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7. Table of Contents
Start Here ................................................................................................................................... 1-1
What’s New in Transportation Manager 6.0.3....................................................................... 1-1
Overview of the Document .................................................................................................... 1-2
Documents Delivered............................................................................................................. 1-3
Document Conventions.......................................................................................................... 1-4
Introduction to Linear Referencing ......................................................................................... 2-1
What is Linear Referencing?.................................................................................................. 2-1
Linear Referencing and GeoSpatial Technology ................................................................... 2-2
LRS Linear Features and Event Data..................................................................................... 2-3
Multilevel Linear Referencing Systems (MLRS) .................................................................. 2-5
Linear Referencing Analysis................................................................................................ 2-14
Linear Referencing System Maintenance ............................................................................ 2-16
Introduction to Working with Multilevel LRSs...................................................................... 3-1
LRS Analysis Using a Multilevel LRS .................................................................................. 3-1
Maintaining a Multilevel LRS ............................................................................................... 3-8
Working with the LRS Metadata Definition Command........................................................ 4-1
The LRS Metadata Definition Command Workflow to Create New Metadata Definitions .. 4-4
The LRS Metadata Definition Command Workflow to Modify an Existing LRS Definition 4-9
Working with the Interactive LRS Calibration Command ................................................... 5-1
The Interactive LRS Calibration Command Workflow ......................................................... 5-2
Working with the LRS Calibration Command....................................................................... 6-1
The LRS Calibration Command Workflow ........................................................................... 6-2
Working with the LRS Validation Command ........................................................................ 7-1
The LRS Validation Command Workflow ............................................................................ 7-2
Working with the Reformat Linear Collections Command .................................................. 8-1
The Reformat Linear Collections Command Workflow........................................................ 8-2
Working with the Create Intersection Markers Command .................................................. 9-1
The Create Intersection Markers Command Workflow ......................................................... 9-4
Working with the Insert LRM Segment Command ............................................................. 10-1
The Insert LRM Segment Command Workflow.................................................................. 10-1
i
8. Working with GeoMedia Transportation Manager
Working with the Split LRM Segment Command ................................................................ 11-1
The Split LRM Segment Command Workflow ................................................................... 11-2
Working with the Redigitize LRM Segment Command ...................................................... 12-1
The Redigitize LRM Segment Command Workflow .......................................................... 12-3
Working with the Merge LRM Segments Command........................................................... 13-1
The Merge LRM Segments Command Workflow............................................................... 13-2
Working with the Delete LRM Segment Command............................................................. 14-1
The Delete LRM Segment Command Workflow ................................................................ 14-1
Working with the Output Linear Datum Command ........................................................... 15-1
The Output Linear Datum Command Workflow ................................................................. 15-3
Working with the Interactive Multilevel LRS Conflation Command ................................ 16-1
The Interactive Multilevel LRS Conflation Command Workflow ...................................... 16-3
Working with the Multilevel LRS Conflation Command .................................................... 17-1
The Multilevel LRS Conflation Command Workflow ........................................................ 17-3
Working with the Multilevel LRS Validation Command .................................................... 18-1
Data Integrity Rules ............................................................................................................. 18-1
Geometry Rules.................................................................................................................... 18-2
LRM Rules........................................................................................................................... 18-4
Schema ................................................................................................................................. 18-6
The Multilevel LRS Validation Command Workflow......................................................... 18-7
Working with the Display LRM Command .......................................................................... 19-1
The Display LRM Dialog Box............................................................................................. 19-1
The Display LRM Command Workflow ............................................................................. 19-3
Working with the LRS Event Overlay Command................................................................ 20-1
The LRS Event Overlay Command Workflow .................................................................. 20-11
Working with the Resolve LRS Event Overlaps Command................................................ 21-1
The Resolve LRS Event Overlaps Command Workflow..................................................... 21-2
Working with the LRS Event Conversion Command.......................................................... 22-1
The LRS Event Conversion Command Workflow .............................................................. 22-1
Working with the Convert Intersection Referenced Events Command ............................. 23-1
The Convert Intersection Referenced Events Command Workflow.................................... 23-1
ii
9. Table of Contents
Working with the LRS Event Generation Command .......................................................... 24-1
The LRS Event Generation Command Workflow ............................................................... 24-2
Working with the Create Intersections and Midblocks Command .................................... 25-1
The Create Intersections and Midblocks Command Workflow........................................... 25-3
Working with the Insert LRS Event Command ................................................................... 26-1
The Insert LRS Event Command Workflow........................................................................ 26-1
Working with the LRS Keys for Coordinate Events Command ......................................... 27-1
The LRS Keys for Coordinate Events Command Workflow............................................... 27-1
Working with the Routes and Sections to LRS Command .................................................. 28-1
The Routes and Sections to LRS Command Workflow....................................................... 28-1
Working with the LRS Event Transform Command........................................................... 29-1
The LRS Event Transform Command Workflow ................................................................ 29-1
Working with the LRS and Marker Properties Dialog Boxes............................................. 30-1
The LRS Properties Dialog Box Workflow for an LRS Feature Class................................ 30-1
The Marker Properties Dialog Box Workflow for a Marker Feature Class ......................... 30-2
Working with the Event Properties Dialog Box.................................................................... 31-1
The LRM-based Event Properties Dialog Box Workflow ................................................... 31-1
The Datum-based Event Properties Dialog Box Workflow................................................. 31-3
Working with the Coordinate System Dialog Box................................................................ 32-1
The Coordinate System Dialog Box Workflow ................................................................... 32-1
Working with the LRS Data Preparation Workflows.......................................................... 33-1
Reformat Linear Collections ................................................................................................ 33-1
Validate and Fix Geometry .................................................................................................. 33-2
Validate and Fix Connectivity ............................................................................................. 33-3
Calibrate the LRS................................................................................................................. 33-5
Validate the LRS .................................................................................................................. 33-5
Fix the LRS .......................................................................................................................... 33-6
Index the LRS ...................................................................................................................... 33-6
Working with Intersection Preparation Workflows............................................................. 34-1
Intersection Preparation for Single Level LRSs................................................................... 34-1
Intersection Preparation for Multilevel LRSs ...................................................................... 34-8
iii
10. Working with GeoMedia Transportation Manager
Working with the Single Level to Multilevel LRS Conversion Workflow ......................... 35-1
Data Model Design .............................................................................................................. 35-1
Source Data Preparation....................................................................................................... 35-3
Data Conversion................................................................................................................... 35-4
Final Touches ....................................................................................................................... 35-4
Working with the LRS Annotation Workflows .................................................................... 36-1
Annotate Digitizing Direction.............................................................................................. 36-1
Annotate Begin and End Measurements .............................................................................. 36-3
Annotate Even Measures Along the LRS ............................................................................ 36-8
Working with the LRS Analysis Workflows ......................................................................... 37-1
Aggregate Point Event Data onto Linear Segments............................................................. 37-1
Aggregate Point Event Data onto Intersections ................................................................... 37-7
Aggregate Linear Event Data within Boundaries .............................................................. 37-12
Aggregate Segment Event Data onto Linear Segments by Proportion .............................. 37-18
Introduction to Routing .......................................................................................................... 38-1
What is a Routing Network? ................................................................................................ 38-1
Edge-Node Connectivity...................................................................................................... 38-2
Impedance ............................................................................................................................ 38-4
Turn Tables .......................................................................................................................... 38-4
Restrictors ............................................................................................................................ 38-6
Stops..................................................................................................................................... 38-8
Routing Analysis.................................................................................................................. 38-9
Routing Maintenance ......................................................................................................... 38-10
Working with the Build Network Command ........................................................................ 39-1
The Build Network Command Workflow............................................................................ 39-1
Working with the Stop Manager Command......................................................................... 40-1
The Stop Manager Workflows ............................................................................................. 40-1
Working with the Turn Editor Command ............................................................................ 41-1
The Turn Editor Workflow .................................................................................................. 41-1
Working with the Restrictor Editor Command.................................................................... 42-1
The Restrictor Editor Workflow .......................................................................................... 42-1
Working with the OneWay Editor Command ...................................................................... 43-1
The OneWay Editor Workflow ............................................................................................ 43-1
Working with the Blockage Editor Command...................................................................... 44-1
The Blockage Editor Workflow ........................................................................................... 44-1
iv
11. Table of Contents
Working with the Display OneWays Command................................................................... 45-1
The Display OneWays Workflow........................................................................................ 45-1
Working with the Display Blockages Command .................................................................. 46-1
The Display Blockages Workflow ....................................................................................... 46-2
Working with the Easy Path Command................................................................................ 47-1
The Easy Path Workflow ..................................................................................................... 47-2
Working with the Best Path Command................................................................................. 48-1
The Best Path Workflow...................................................................................................... 48-2
Working with the Find Closest Stops Command.................................................................. 49-1
The Find Closest Stops Workflow ....................................................................................... 49-2
Working with the Network Coverage Command ................................................................. 50-1
The Network Coverage Command Workflow ..................................................................... 50-2
Working with the Generate Path Directions Command ...................................................... 51-1
The Generate Path Directions Command Workflow ........................................................... 51-1
Working with the Configure Network Dialog Box ............................................................... 52-1
The Configure Network Dialog Box Workflow .................................................................. 52-1
Working with the Stop Properties Control ........................................................................... 53-1
The Stop Properties Control Workflow ............................................................................... 53-1
Working with the Routing Data Maintenance Workflows .................................................. 54-1
The Dynamic Routing Data Maintenance Workflow .......................................................... 54-1
Manual Routing Data Maintenance – The Initial Network Creation Workflow.................. 54-2
Manual Routing Data Maintenance – The Network Update Workflow .............................. 54-3
The Routing Network Validation Workflow ..................................................................... 54-10
Working with the LRS-based Routing Restrictions Workflow........................................... 55-1
A. How to Reach Intergraph.................................................................................................... A-1
Electronic Self-Help Support ................................................................................................ A-1
B. GeoMedia Transportation LRS Data Structures...............................................................B-1
Overview................................................................................................................................B-1
Single Level LRS Data Structures .........................................................................................B-2
Additional Multilevel LRS Data Structures .........................................................................B-13
Event Data Structures...........................................................................................................B-14
v
12. Working with GeoMedia Transportation Manager
Additional Multilevel LRS Event Structures .......................................................................B-19
Multilevel LRS Supporting Tables ......................................................................................B-21
GeoTrans Transportation Data Model….............................……………………………….B-24
C. Working With Oracle LRS and ArcView Data ................................................................ C-1
Working with Oracle LRS Data .............................................................................................C-1
Working with ArcView Data .................................................................................................C-1
Index .......................................................................................................................................... IN-1
vi
13. Start Here
What’s New in Transportation Manager 6.0.3
The major new feature of GeoMedia Transportation Manager 6.0.3 is the option to create
and use Multilevel LRSs. This is important functionality that addresses many common
problems facing transportation agencies, including:
• Handling multiple linear referencing methods – This allows Event data collected using
a wide variety of route measurement and naming schemes to be used together when
analyzing a transportation system.
• Handling multiple network representations – This harmonizes the use of multiple
network representations that perhaps originate from other transportation agencies at
different levels of government. You can choose to analyze your Event data using any
of the available network representations.
• Securing Event data location stability – One of the dangers of a linear referencing
system is that as the network changes (for example, road name changes, realignments,
and recalibrations), the location of Event data can be incorrectly changed.
Intergraph’s Multilevel LRS can prevent this from happening.
• Preserving the history of the network – When used with GeoMedia Transaction
Manager, Intergraph’s Multilevel LRS provides the ability to create, maintain, and
analyze a temporal history of a linear referencing system and the Event data associated
with it. This is a powerful tool for analyzing the effectiveness of maintenance and
corrective actions executed by the agency.
Of course GeoMedia Transportation Manager also has the tools to create and maintain a
Multilevel LRS. Beyond the introduction of Multilevel LRS support, this release also
provides important new functionality in the following areas:
• LRS Conflation – Conflation, the selective copying of data from one source to
another, is especially tricky for transportation networks due to the fact that no two
representations of the same network are modeled or segmented in the same way. The
conflation tools in this release overcome those obstacles. Furthermore, when used in
conjunction with the tools in the GeoMedia Fusion product, GeoMedia Transportation
Manager can perform conflation for an entire data set in a very automated manner.
• LRS Definitions – With this release, the LRS Property settings can be stored centrally
in your enterprise database where they can be set once and be available to all users.
• Region IDs – We have introduced the concept of Region IDs, which allows you to
subdivide your network into logical units. This often improves performance when the
entire network is not needed for a particular analysis.
1-1
14. Working with GeoMedia Transportation Manager
• Intersection-referenced Events – We now support Event data that is located by its
distance and direction from intersections. This even includes the capability to resolve
ambiguous locations associated with roads that cross more than once.
• Aggregation – Often transportation agencies like to analyze their network at
intersections and the “midblocks” between intersections. This release provides a tool
to make these analyses easier, more accurate, and the end results more useful.
• Routing improvements – This release has two improvements to our routing tools.
One is the option to enforce turn restrictions at intermediate stops, which is important
for applications such as large vehicle routing. Another improvement is the ability to
edit the restrictors used by an existing path query via the Query Properties dialog
box, which facilitates what if analyses.
Overview of the Document
This document contains information on using GeoMedia Transportation Manager for linear
data analysis and routing analysis. The structure of this document is as follows:
• There are two major divisions: Chapters 2-37 pertain to Linear Referencing Systems
(LRS), and Chapters 38-55 pertain to Network Routing.
• Chapter 2 provides an introduction to the basic concepts behind linear referencing, and
Chapter 3 provides a good overview of how to work with Multilevel LRSs.
• Chapters 4-18 provide step-by-step instructions on how to use each of the LRS (Linear
Referencing System) Maintenance commands.
• Chapters 19-29 provide step-by-step instructions on how to use each of the LRS
Analysis commands.
• Chapters 30-32 provide step-by-step instructions on how to use four of the elements
common to many of the LRS commands included in this product: the LRS Properties
dialog box, the Markers Properties dialog box, the Event Properties dialog box, and
the Coordinate System dialog box.
• Chapters 33-37 provide instruction on common workflows used in the preparation and
analysis of linear data.
• Chapter 38 provides an introduction to the basic concepts behind network routing.
• Chapters 39-46 provide step-by-step instructions on how to use each of the Routing
Maintenance commands.
• Chapters 47-51 provide step-by-step instructions on how to use each of the Routing
Analysis commands.
• Chapters 52-53 provide step-by-step instructions on how to use two of the elements
common to many of the Routing commands included in this product: the Configure
Network dialog box and the Stop Properties control.
1-2
15. Start Here
• Chapters 54-55 provide instruction on common workflows used in Routing
maintenance and analyses.
• Appendix B provides details of the LRS data structures supported by the GeoMedia
Transportation product line.
• Appendix C provides instruction for using Oracle LRS or ArcView data with the
GeoMedia Transportation product line.
Each section of this document takes you through a systematic process to use the software
commands.
Documents Delivered
The following online documents are delivered with GeoMedia Transportation Manager:
Document Number Description
Working with DJA0845 An overview of the workflows and commands for
GeoMedia Online only performing most software tasks. Available online in
Transportation .pdf format at Start > All Programs > GeoMedia
Manager Transportation Manager > User Documentation >
Working with GeoMedia Transportation Manager.
Installing DJA0853 Instructions for installing the product. Available online
GeoMedia Online only in .pdf format at Start > All Programs > GeoMedia
Transportation Transportation Manager > User Documentation >
Manager Installing GeoMedia Transportation Manager.
GeoMedia Online only Programmer's guide for objects, methods, and
Transportation properties. Available from the Program
Manager Object FilesGeoMediaHelp folder or at Start > All Programs >
Reference GeoMedia Transportation Manager > Developer
Documentation > GeoMedia Transportation Manager
Object Reference.
GeoMedia Online only Object diagrams for programmers. Available online in
Transportation .pdf format at Start > All Programs > GeoMedia
Object Diagrams Transportation Manager > Developer Documentation >
GeoMedia Transportation Object Diagrams.
GeoMedia Online only Workflow diagrams for programmers. Available online
Transportation in .pdf format at Start > All Programs > GeoMedia
Workflow Transportation Manager > Developer Documentation >
Diagrams GeoMedia Transportation Workflow Diagrams.
Visit our web site at http://support.intergraph.com/Documentation.asp for the latest
version of these documents.
1-3
16. Working with GeoMedia Transportation Manager
Document Conventions
Typeface Conventions Used in the Documents
ALL CAPS Keyboard keys.
If keys are separated by a comma, press them in
sequence. For example: ALT, F5. If they are
joined by a plus sign, press them at the same time.
For example: CTRL+z.
Bold An item in the graphical interface, such as the title
unserifed of a dialog box or a tool. Paths through menus use
type right angle brackets between items you select.
For example: Select File > Open to load a new file.
Courier Information you type.
type
For example: Type original.dat to load the
ASCII file.
Italic type A document title, the first occurrence of a new or
special term, folder and filenames, or information
about what the software is doing.
1-4
17. Introduction to Linear Referencing
The purpose of this chapter is to outline the basic concepts behind the linear referencing
capabilities of GeoMedia Transportation Manager. Both single-level and Multilevel linear
referencing systems (LRSs) are described in some detail. Lastly, the various LRS analysis
and maintenance tools are described.
What is Linear Referencing?
Linear Referencing is simply the tracking and analysis of data that is associated with
locations along a linear network. Some road transportation examples include tracking the
location of and condition of signage, the condition of pavement, and the location and
severity of accident occurrences. The biggest uses of linear referencing are Asset Tracking
and Asset Analysis.
Asset Tracking primarily encompasses the following
four items:
• What, where, and when of the assets (for example,
a pothole at kilometer post 41.7 along Route 66,
reported June 6th, 2002)
• Asset conditions (for example, a stretch of
pavement with rutting and cracking)
• Incidents along the network (for example, a traffic
accident)
• Activities along the network (for example,
construction projects)
Asset Analysis includes such activities as “hot-
spotting” (finding areas with an unusual density of a
given type of problem) and cross-discipline analysis
(for example, cross analyzing areas that have both run-
off-the-road accidents and no guardrails). This type of
analysis can be important for any number of areas, including the following:
• Protecting the public (for example, finding areas of high-density accidents and finding
the common contributing factor)
• Optimizing usage of assets (for example, locating areas with both high volume and low
number of lanes in order to identify areas of congestion)
• Optimizing budget usage (for example, locating the areas with the most traffic and the
worst pavement conditions to be first priority for resurfacing)
2-1
18. Working with GeoMedia Transportation Manager
Linear Referencing and GeoSpatial Technology
The main impetus to merge linear referencing with geospatial technology can be summed
up simply: it is often desirable to view location data on a map. It also opens up a lot of
other analysis capabilities, such as summing up data within an area feature (for example,
the kilometers of rail track that require maintenance within a given jurisdiction) or finding
data within a proximity of linearly referenced data (for example, finding residences within
a buffer zone of a construction project).
Using GeoMedia Transportation Manager is not the only way to merge linear referencing
and geospatial technology, but it is certainly the easiest. GeoMedia Transportation
Manager enables you to create map features, including pavement conditions, accident data,
and average daily traffic. This kind of information will help you plan improvements for
deteriorating assets, will identify where your organization is spending its money, and will
provide critical information clearly and accurately to all participants involved in your
projects. GeoMedia Transportation Manager increases the value of your data by turning it
into business-critical, decision-support information.
4.1
3.2
3
2 1.8
Hwy 6
0.9
The preceding diagram shows a portion of road on the left and its geospatial representation
on the right. The road has kilometer posts that indicate cumulative linear measures along
the road. It also has a road name, Highway 6 in this example. A section of fencing along
the road is also shown in both the left and right views. Based on the kilometer posts, it can
be determined in the field that this stretch of fence runs along Highway 6 from kilometer
measure 2.0 to 2.6.
On the geospatial side, we have three linear features, known as LRS Linear Features, that
will all have a road name and begin and end measure attribution. These LRS Linear
Features are the backbone of the LRS and are used in automating the mapping of linearly
referenced data, such as this stretch of fencing, onto our map view.
2-2
19. Introduction to Linear Referencing
Of course, this mapping of linearly referenced data does not have to be automated. Without
GeoMedia Transportation Manager, you can estimate where kilometer measures 2.0 and
2.6 are along the road, and then you can digitize a linear feature between these two points
and along the road. This is not too hard for a few features, but what if you have a tabular
report for hundreds or thousands of linearly referenced items that you want to map? With
GeoMedia Transportation Manager, all of these items can be mapped with a single
command.
The methodology used by GeoMedia Transportation Manager to do this bulk mapping of
linearly referenced tabular data is called Dynamic Segmentation (or linear geocoding). This
methodology interpolates the location of linearly referenced data along the LRS Linear
Features by making use of the road (or rail, ferry line, and so on) name and measurement
attributes stored on those features.
LRS Linear Features and Event Data
As mentioned before, LRS Linear Features are the backbone of the LRS. But working with
the linearly referenced tabular data, known as Event Data, is the whole reason for building
the LRS in the first place. Although the data structures of these two components are
described in detail in Appendix B: GeoMedia Transportation LRS Data Structures, we will
provide a brief summary here of what is known as traditional, or single-level, LRS. We
will address Multilevel LRS (MLRS) in the next section.
The LRS Linear Features represent the network itself. Each LRS Linear Feature table is a
linear feature class that has the following fields:
• ID – This is a long integer value that uniquely identifies each feature within the table.
• LRSKeys1-4 – This is one to four fields that together define the “route” that this
feature belongs to.
• StartMeasure – This is a numeric value that contains the measurement value for the
beginning of this feature.
• EndMeasure or Duration – This is a numeric value that contains either the
measurement value for the end of this feature or the length measurement for this
feature.
• BeginMarker (optional) – This field stores a name for the beginning position of this
feature. This is referred to as an internal marker.
• EndMarker (optional) – This field stores a name for the end position of this feature.
This is referred to as an internal marker.
• ReversedGeometry (optional) – This Boolean (True/False) field declares whether the
GeoMedia Transportation Manager software should treat this linear feature as if (False)
or as if its digitizing direction were reversed and its beginning were its end, and vice-
versa (True).
2-3
20. Working with GeoMedia Transportation Manager
The Event Data represents the linearly referenced data. Note that Event Data can either be
point data (occurring at just one spot on the linear network) or linear data (occurring at a
span of distance along the linear network). Each Event Data table is (usually) a non-
graphic table that has the following fields:
• ID – This is a long integer value that uniquely identifies each record within the table.
• LRSKeys1-4 – This is one to four fields that together define the “route” that this record
lies along.
• Measurement data (pick one of the following options)
- Measure Option – For point event data, this consists of one numeric Measure field
that indicates the relative location of the point event record on the “route” defined
by the LRS Key fields. For linear event data, this consists of two numeric fields: a
StartMeasure field and an EndMeasure field. These define the relative location of
the start and end points of the linear event record on the “route” defined by the
LRS Key fields.
- Marker Offset Option – For point event data, this consists of a Marker name
field and a numeric Offset distance field. The point event data is located by
first locating the marker and then by adding the offset distance to that location.
For linear event data, there are two Marker fields and two Offset fields
defining the start and end of the linear event record.
- Coordinate Option – For point event data, this consists of two fields which,
depending on the referenced Coordinate System File, may by either projected
coordinates (for example, Northing & Easting) or geographic coordinates
(Latitude & Longitude). For linear event data, there are four fields defining the
coordinates for both the start and the end of the linear event record.
- Duration Option – This is a slight variation on the Measurement Option and
only applies to linear event data. It consists of a StartMeasure field and a
Duration (or Length) field that together define the relative location of the
record along its “route.”
• Other Attributes (optional) – These are optional, but they are also the whole reason for
doing linear referencing. For bridge events, these will store bridge data; for accident
events, they will store accident data; and for pavement events, they will store pavement
data.
Optional components of the LRS that we have not discussed as yet are the External
Markers. External Markers mark points along the network just like the Internal Markers
discussed earlier, but these are not bound to just the beginning and end of LRS Linear
Features. External Markers can occur anywhere along the LRS network and are
functionally equivalent to point event data using the Measure option. They are useful for
modeling milestones and monuments that are commonly used to measure locations from.
They can be used, along with Internal Markers, to locate event data using the Marker
Offset option.
2-4
21. Introduction to Linear Referencing
Each External Marker table is (usually) a non-graphic table that has the following fields:
• ID – This is a long integer value that uniquely identifies each record within the table.
• LRSKeys1-4 – This is one to four fields that together define the “route” that this record
lies along.
• Measure – This is a numeric field that indicates the relative location of the External
Marker on the “route” defined by the LRS Key fields.
• MarkerName – This field stores a name for this Marker.
Detailed information on how to create a LRS Linear Feature class is provided in the “LRS
Data Preparation Workflows” chapter. Information on at least one way to populate Event
Data and External Marker tables is provided in the “Working with the Insert LRS Event
Command” chapter.
Multilevel Linear Referencing Systems (MLRS)
GeoMedia Transportation Manager and GeoMedia Transportation Analyst now support
Multilevel LRSs (MLRS) as well as the traditional, single-level LRSs. Multilevel LRS has
been a topic of discussion since at least the early 1990s and the original NCHRP (National
Cooperative Highway Research Program) 20-27 study. The Multilevel LRS model that
Intergraph uses is known as the GeoTrans model and is derivative of the NCHRP 20-27
model.
Since the inception of the concept of Multilevel LRS, there have been numerous
implementations and attempted implementations. The reason for the interest is very
understandable. This kind of model addresses a variety of problems that are common to
almost all transportation agencies, which raises the question as to why this kind of model is
not more common. First, let’s summarize some of the problems a Multilevel LRS solves,
and then we will explore why these models are not in use everywhere.
Multiple Linear Referencing Methods
Perhaps the key issue addressed by Multilevel LRSs is the need to support multiple Linear
Referencing Methods (LRMs). Most transportation agencies have various sub departments
and external sources that collect data about their transportation network using a variety of
different measurement methods and sometimes different road- or rail-naming conventions.
A few example LRMs are shown here:
2-5
22. Working with GeoMedia Transportation Manager
County Border
State Border
175 Main St.
Route 50 Main St.
87.60 mi Address Range:
100 to 200
State Cumulative Street Address
with Spruce Ave.
with Elm Ave.
County Border
Intersection
Intersection
State Border
Route 50 Main St.
5.4 mi 200 ft East
County Cumulative Marker Offset
Support of these different LRMs is key to being able to compile the data collected by these
different methods for analysis. For example, if accidents are located by GPS and guardrail
inventory is located by milepost, then you would need to be able to use these different
LRMs together in order to locate an accident in which a car runs off the road where there is
no guardrail.
Multiple Geometric Representations
Another issue that can be addressed by Multilevel LRSs is the need that many
transportation agencies have to support more than one geometric representation of their
network. One case for this is where different levels of generalization are used for different
map products. Agencies would like to be able to use the same event data (also known as
distributed attribute data) against different geometric representations, depending on
whether they are doing large-scale or small-scale analysis.
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23. Introduction to Linear Referencing
A second common use case for multiple geometric representations is where some of the
data comes from a regional agency and some of it comes from one or more local agencies.
There may be considerable overlap of the data coverage, but there may also be many roads
covered by the local data that are not covered by the regional data. For some analyses, the
user will want to see all of the local roads; but for others, he or she will only want to use
the major roads.
Without a Multilevel LRS, users have to duplicate 100% of their LRS data maintenance
efforts for each geometric representation that they want. And even then, they are not
assured that each LRS is in sync with the other and will give similar analysis results.
Agencies want to be able to easily switch back and forth between geometric
representations without worrying if this will affect the validity of their analysis. This is
possible with Multilevel LRSs.
2-7
24. Working with GeoMedia Transportation Manager
Event Location Stability
One of the toughest challenges facing managers of transportation information is how to
handle the effects of changes that are made in the transportation network over time. These
changes include road-name changes, realignments, recalibrations, and so on. To illustrate
these effects, we have an example of a small piece of a network with some point and linear
event data associated with it. We will say that the point events represent accident locations
along a road and that the linear event represents pavement conditions. This is our “before”
picture:
Before network changes
0 5 7 11 13 18
Now let’s see what happens to our data when our road gets realigned and recalibrated.
Because dynamic segmentation is an interpolation based on the road names, measures, and
geometry, all of these changes can cause our linearly referenced event data to shift
locations with a traditional LRS. In this case, these errors show accident data where
accidents never happened, and they show pavement conditions for a now-abandoned piece
of roadway as if the data relates to a new stretch of road.
After network changes
– with Single Level LRS
0 5 7 11 13 18
10 12 17
Now let’s look at this same example using the GeoTrans data model, which has some
special features to address this particular problem. Here we see that our accidents and
pavement conditions do not shift. Furthermore, these pavement conditions show up only on
the segments of the road on which this data actually occurred – even with linear event data.
After network changes
– with GeoTrans model
0 5 7 11 13 18
10 12 17
2-8
25. Introduction to Linear Referencing
Data with incorrect locations is bad data and can lead to bad decisions. So, the desired
effect is that we should see those events, and only those events, that pertain to the current
version of the network. This should work for both point and linear events. GeoMedia
Transportation Manager and the GeoTrans data model make this possible.
To take this further, many agencies would like to be able to look at the state of their
networks for a specific time period and to see only those events that pertain to those
networks as they existed at that specific time. When GeoMedia Transportation Manager is
used in conjunction with GeoMedia Transaction Manager, this type of temporal analysis
and temporal data management is made easy. This is discussed in more detail below and in
the “Working with Multilevel LRSs” chapter.
Why do so few transportation agencies use MLRS?
In the last few sections, we have seen a few of the important benefits (there are others) of
using Multilevel LRS. So why are most transportation agencies still using traditional,
single-level LRS?
Part of the reason is that implementations have been costly because of the lack of
availability, until now, of an off-the-shelf solution. Implementations have had to be
custom. The toughest part of these custom implementations has not been analysis, but
rather it has been data maintenance. As we will see in the next section, the data in the
GeoTrans model is spread over multiple, connected layers. Because of this, a single change
affects multiple layers and the relationships between those layers. Because of this, it is
understandable that the hardships associated with Multilevel LRSs have been too high a
hurdle for most agencies to overcome.
GeoMedia Transportation Manager has overcome these obstacles by providing a tool that
is available off-the-shelf that integrates the benefits of Multilevel LRS with the tools used
to maintain and make use of it. So GeoMedia Transportation Manager, while also
supporting traditional, single-level LRS, also has a complete set of tools for building,
maintaining, and analyzing a Multilevel LRS. These tools are designed to take much of the
complexity out of using this powerful model, while still giving all of the benefits. This will
allow for better, more accurate, and more complete analyses of transportation data and will
make the promise of Multilevel LRS a reality.
GeoTrans Data Model
In this section, we review the development and structure of the GeoTrans data model that is
the core of our MLRS solution. As mentioned before, the GeoTrans data model is
derivative of the NCHRP 20-27 model. However, we have made some tweaks to improve
event location stability and temporality and to allow for more flexible segmentation.
Before we get into the GeoTrans data model let’s start by looking at a logical
representation of the traditional, single-level LRS. A single-level LRS consists of an LRS
linear feature class with geometry, name, and measurement data. This LRS linear feature
class is the foundation for linearly referencing any number of event tables. The LRS
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26. Working with GeoMedia Transportation Manager
Linear feature class and the event tables are “joined” via dynamic segmentation. This
model works fine for a static network with just one LRM and just one geometric
representation of the network and has been the state of the art for years.
Event Event Event
1 2 N
LRS
Now, what do we do if we have a network that changes over time (road-name changes,
realignments, and so on), if we have more than one LRM, or if we have more than one
geometric representation of our network? The theory behind Multilevel LRS is to abstract
out into separate entities those parts of the network that change independently. Towards
that end, we have abstracted the route naming and measurement part into an LRM layer
that can contain any number of LRMs. We have also abstracted the geometric
representation part into a Geometry layer that can contain any number of physical
representations of our network. We have tied both of these to a Linear Datum. The Linear
Datum acts as a non-changing anchor that these other layers can tie to. A unique feature of
the GeoTrans model is that the Linear Datum records can neither be edited nor deleted.
They can only be added to when there are new roads or realignments. This permanence is,
as we shall see, the key to Event Location Stability.
Event Event Event Event Event Event Event Event Event
1/1 1/2 1/N 2/1 2/2 2/N N/1 N/2 N/N
Event
Data
LRM LRM LRM
1 2 N
Linear
Referencing
Methods
Linear Datum Datum
Cartographic Geom Geom Geom
Representations 1 2 N
So from a practical stand point, how do we relate the individual LRMs and Geometries
back to the Linear Datum? When we need a one-to-one or a one-to-many relationship in a
database, we use a Join where one field in one table exactly matches a field in another
table. However, if we do not want to force our model to have all geometries and LRMs
segmented identically, then what we have is a many-to-many relationship. This is handled
by having an intermediate table to store the relationship. The ability to have completely
independent segmentation is a unique feature of the GeoTrans data model. We accomplish
this by not using a standard many-to-many join, but rather by using dynamic segmentation
to establish our relationships.
2-10
27. Introduction to Linear Referencing
In the following diagram, we show the intermediate tables that store this many-to-many
relationship. We call these cross reference tables (G-D xRef refers to Geometry to Datum
cross reference, and L-D xRef refers to Datum to LRM cross reference). The diagram also
shows the multilevel dynamic segmentation that relates each of these tables together. This
complexity is handled for you by the software so that you get the benefits of the model
without the extra trouble.
LRM
Event BegMeas EndMeas Attributes
Key(s)
LRM Rev
LRM LRMID BegMeas EndMeas
Key(s) Geom
Datum LRM
L-D xRef
ID BegMeas EndMeas ID BegMeas EndMeas
Linear Datum DatumID Length Description
Geometry Datum
G-D xRef
ID BegMeas EndMeas ID BegMeas EndMeas
Geometry GeomID BegMeas EndMeas Geometry
Another key part of the model pertains to our Event Location Stability methodology. By
way of contrast, we will describe two common alternative methods that some have used to
accomplish this same thing.
The first alternative method is sometimes referred to as Permanent Event Geometry, which
simply means storing geometry created during dynamic segmentation permanently with the
event data. The upside of this methodology is its simplicity. One downside is that it only
works well if you have only one geometric representation and you never expect to update it
with newly collected geometry. Another downside is that it does not handle temporality
well. If a road gets realigned, this method will still show event data along the old alignment
that no longer exists.
The second alternative method is sometimes referred to as Cascading Edits. This method
develops database triggers that will change the measures of all event data associated with
an LRS any time the LRS changes. The upside of this method is that the custom code it
contains gives a lot of flexibility. However, it has several downsides. First, as in most
transportation agencies, there could be a performance issue when a large number of tables
are affected. Second, it assumes that all event tables are stored in the central database and
thus are accessible to these triggers. Third, this problem is fairly difficult to implement for
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28. Working with GeoMedia Transportation Manager
events associated with the segment of the LRS that is actually changed. Lastly, it has the
additional problem that once the measures are changed, they no longer are in the correct
location in relation to the “old” version of the LRS. This creates an event location stability
problem if you try to look at a temporal view of the data the way it once was. Thus this
method is ill-suited for temporal analysis.
The method we have implemented in the GeoMedia Transportation products and the
GeoTrans data model is called Event Registration. The downside of this method is that it
requires users to do a one-time Event Registration step whenever they bring in new event
data. The upside is that it has none of the downsides described above.
The Event Registration step is done with the LRS Event Transform command (see the
“Working with the LRS Event Transform Command” chapter). One of the options of this
command is to convert LRM-based names and measures on Event tables to Datum-based
names and measures. Once this simple step is done, this event data can be used regardless
of how the network changes over time. Road names can change, routes can be recalibrated,
and realignments may occur – but the event data will still locate correctly.
The following figure shows the complete GeoTrans logical model. Note that this model
shows some events as “LRM” Events and others as “Datum” Events. The Datum Events
are those that have gone through Event Registration and thus will receive the benefit of
Event Location Stability. Also shown on this diagram are the two types of external markers
now supported by the GeoTrans data model. The ones labeled “LRM” Markers are the
same as those used by traditional, single-level LRS. The ones labeled “Datum” Markers are
LRM Markers that have gone through Event Registration and, therefore, have the same
location stability as Datum Events.
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29. Introduction to Linear Referencing
Event Event Event
1/1 1/2 1/N
Event Event Event
2/1 2/2 2/N
‘LRM’ Events
Event Event Event
N/1 N/2 N/N
LRM LRM LRM
1 2 N
‘LRM’
Markers
xRef xRef xRef
1 2 N
Event
D/1
Event
Linear Datum
D/2
‘Datum’
Markers
Event
D/N
‘Datum’ Events xRef xRef xRef
1 2 N
Geom Geom Geom
1 2 N
Another important consideration in the design of this model is support for temporality.
Many agencies want to not only be able to analyze their transportation network as it is –
but also how it was (for trend analysis) or how it might be (for design and planning
purposes). When you use the GeoMedia Transportation products with GeoMedia
Transaction Manager, you can automatically store historical versions of the network as it is
being edited in order to represent the latest changes to your network. Likewise, you can
model designs for future changes to the network without destroying the current
representation. With events that have been registered, you can view both the network and
linearly referenced event data correctly for any time for which you have data. (Please note
that GeoMedia Transaction Manager is not required in order for you to use the GeoMedia
Transportation products, but without it only current network analysis is possible.)
More details about the GeoTrans data model are discussed in Appendix B: GeoMedia
Transportation LRS Data Structures.
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30. Working with GeoMedia Transportation Manager
Linear Referencing Analysis
This section provides brief descriptions of the major LRS Analysis tools provided by
GeoMedia Transportation Manager. Detailed instructions on how to use each of these
commands is provided elsewhere.
Display LRM – This command creates an LRM query and works with either single-level
or Multilevel LRSs. It works in conjunction with the LRS Metadata command, which is
used to populate the choices the user has. For an MLRS, those choices are which LRM and
Geometry to use. For single-level LRSs, the choice is only which single-level LRS to use.
In both cases, the resultant query carries along metadata which simplifies the use of many
of the other commands. When this query is used as the LRS Feature Class, the appropriate
LRS Properties are automatically filled in. For more information see the “Working with the
Display LRM Command” chapter.
Dynamic Segmentation – This command, which has already been referred to above, takes
linearly referenced tabular data and creates a graphic query class from it that can be viewed
in the map view. This lets you visualize your organization's inventory of assets more
clearly than by simply reviewing tabular data. For more information see the “Linear
Referencing” chapter in Working with GeoMedia or Working with GeoMedia Professional.
Note: The Dynamic Segmentation command is now located on the GeoMedia
Professional menu bar under Analysis.
LRS Event Overlay – This command compares two different Event Data tables and
calculates intersections, differences, or unions of the two tables and presents the results as a
graphic query class that can be viewed in the map window. An example of this is to map
all the locations with run-off-the road accidents and no guard rails. For more information
see the “Working with the LRS Event Overlay Command” chapter.
Resolve LRS Event Overlaps – This command takes a single linear Event Data table and
provides a very user-definable method for removing overlaps in the data. For example, in a
table of pavement conditions you may have many overlapping records, but you may want
to only see the most current pavement condition records. For more information see the
“Working with the Resolve LRS Event Overlaps Command” chapter.
LRS Precision Location – This command allows you to get real-time LRS locations of
your cursor location in the map view. It also allows you to use key-ins of LRS locations to
place points in the map view. These points may just be used for orientation, but they also
can be used for placing vertices of new geometry. For more information see the “Linear
Referencing” chapter in Working with GeoMedia or Working with GeoMedia Professional.
Note: The LRS Precision Location command is now located on the GeoMedia
Professional menu bar under Tools.
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31. Introduction to Linear Referencing
LRS Event Conversion – This command allows you to convert the measurement portion
of your event data from one measurement option to another (these options were described
earlier). This can allow you, among other things, to convert event data collected in a
number of ways to a single measurement method for more consistent reporting. For more
information see the “Working with the LRS Event Conversion Command” chapter.
Convert Intersection-referenced Events – This command takes intersection-referenced
event data and converts it into marker-offset event data that is compatible with the
GeoMedia Transportation products. It has a special tool for handling the ambiguity
associated with intersection-referenced event data associated with roads that cross more
than once. This command works in conjunction with the Create Intersection Markers
command. For more information see the “Working with the Convert Intersection
Referenced Events Command” chapter.
LRS Event Generation – This command provides you with a number of ways to generate
event data at various defined points along the LRS network. This comes in handy for both
annotation and aggregation workflows. For more information see the “Working with the
LRS Event Generation Command,” “LRS Annotation Workflows,” and “LRS Analysis
Workflows” chapters.
LRS Keys for Coordinate Events– This command will take Event data that has coordinate
data but no LRS Key data and add the LRS Key data to it. This will make this kind of
Event Data, commonly collected using GPS instruments, usable with the other analysis
commands, such as Dynamic Segmentation and LRS Event Overlay. For more
information see the “Working with the LRS Keys for Coordinate Events Command”
chapter.
Routes and Sections to LRS – This command takes the two component classes from an
ArcRoute system (Routes and Sections) and creates a single query of an LRS class that is
usable with the other commands within GeoMedia Transportation Manager. For more
information see the “Working with the Routes and Sections to LRS Command” chapter.
Insert LRS Event – This command allows you to interactively create event data by
clicking on the map view to define LRS key, begin measures, and (for linear events) end
measures. This will allow you to create event data via “heads-up” digitizing. For more
information see the “Working with the Insert LRS Event Command” chapter.
LRS Event Transform – This is an MLRS command that can transform an event feature
class in any of the following ways:
• LRM-based to Datum-based Event feature class (Event Registration)
• Datum-based to selected LRM-based Event feature class in the same linear referencing
system
• Source-LRM-based to target LRM in the same linear referencing system
For more information see the “Working with the LRS Event Transform Command”
chapter.
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32. Working with GeoMedia Transportation Manager
Linear Referencing System Maintenance
This section provides brief descriptions of the major LRS Maintenance tools provided by
GeoMedia Transportation Manager. Detailed instructions on how to use each of these
commands is provided elsewhere. A good overview of LRS maintenance is provided in the
“LRS Data Preparation Workflows” chapter.
LRS Metadata Definition – This command provides the capability to define and modify
LRS Metadata for either single-level or Multilevel LRSs. This allows a one time
identification of the key tables and fields associated with the LRS so that others can make
use of this definition without duplication of effort. This command works closely with the
Display LRM command in order to simplify the use of the various LRS Analysis and
Maintenance commands. For more information see the “Working with the LRS Metadata
Definition Command” chapter.
Interactive LRS Calibration – This command can be used to name and calibrate (that is,
populate measure values in) LRS features one route at a time. For more information see the
“Working with the Interactive LRS Calibration Command” chapter.
LRS Calibration – This command can be used to calibrate (that is, populate measure
values in) LRS features an entire feature class at a time. For more information see the
“Working with the LRS Calibration Command” chapter.
LRS Validation – This command can be used to validate that a linear feature class is also
a working LRS feature class that will provide accurate results. It queues up errors for easy
correction. For more information see the “Working with the LRS Validation Command”
chapter.
Reformat Linear Collections – This command can be used to repair some of the problems
common to data sets containing geometry collections. It assures that components of
geometry collections are in order and have correct and consistent digitizing directions. This
helps assure an LRS that provides correct analysis results. For more information see the
“Working with the Reformat Linear Collections Command” chapter.
Create Intersection Markers – This command creates an Intersection Markers feature
class for an input LRS feature class. The Intersection Markers feature class will be a point
feature class that represents all valid intersections in the input LRS feature class. This
command is used in conjunction with the Convert Intersection-referenced Events
command. For more information see the “Working with the Create Intersection Markers
Command” chapter.
Create Intersections and Midblocks – This command creates two feature classes. The
Intersection feature class covers the portions of the network within a user-specified
distance of each valid intersection and has attribution identifying associated roads. The
Midblock feature class shows that portion of the network in between these Intersection
features and also includes identifying attribution. Both of these feature classes are very
useful in aggregation workflows. For more information see the “Working with the Create
Intersections and Midblocks Command” chapter.
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33. Introduction to Linear Referencing
Insert LRM Segment – This command is a special MLRS command to simplify the task
of inserting new features into a Multilevel LRS dataset. For more information see the
“Working with the Insert LRM Segment Command” chapter.
Split LRM Segment – This command is a special MLRS command to simplify the task of
splitting features in a Multilevel LRS dataset. For more information see the “Working with
the Split LRM Segment Command” chapter.
Redigitize LRM Segment – This command is a special MLRS command to simplify the
task of redigitizing features or portions of features in a Multilevel LRS dataset. For more
information see the “Working with the Redigitize LRM Segment Command” chapter.
Merge LRM Segments – This command is a special MLRS command to simplify the task
of merging features in a Multilevel LRS dataset. For more information see the “Working
with the Merge LRM Segments Command” chapter.
Delete LRM Segment – This command is a special MLRS command to simplify the task
of deleting features in a Multilevel LRS dataset. For more information see the “Working
with the Delete LRM Segment Command” chapter.
Output Linear Datum – This command provides the capability to display the linear
datum graphically. It has special abilities to show the entire datum even if the entire datum
is not represented in any one geometric definition. This command is primarily used by the
two LRS Conflation commands. For more information see the “Working with the Output
Linear Datum Command” chapter.
Interactive Multilevel LRS Conflation – This command can be used to update an existing
MLRS with new data from a separate linear feature class. In the Update mode of this
command, the user identifies the related portions of both the new and existing data and which
LRM and/or Geometry tables to update (while maintaining Linear datum definitions). In Insert
mode, the user needs only to identify the pertinent potions of the new data and what LRM
and/or Geometry tables to add to. For more information see the “Working with the
Interactive Multilevel LRS Conflation Command” chapter.
Multilevel LRS Conflation – Like the Interactive Multilevel LRS Conflation command, this
command can be used to update an existing MLRS with new data from a separate linear feature
class. The difference is that instead of interactively identifying related portions of new and
existing data, this command makes use of the Links database, which can be populated using
GeoMedia Fusion. Even without GeoMedia Fusion, this command is useful for converting
single-level LRSs into MLRSs. For more information see the “Working with the Multilevel
LRS Conflation Command” chapter.
Multilevel LRS Validation – This is an Oracle-only command used to validate the
MLRSs. It works in conjunction with the LRS Validation command to find MLRS data
errors. For more information see the “Working with the Multilevel LRS Validation
Command” chapter.
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35. Introduction to Working with
Multilevel LRSs
This chapter provides general guidance for working with Multilevel LRSs. The focus is on
how to make use of a Multilevel LRS after its initial creation. It covers using this kind of
LRS for analysis as well as the maintenance of the LRS. Therefore, this chapter is broken
into two major sections: LRS Analysis using a Multilevel LRS
• Maintaining a Multilevel LRS
Before reading this chapter, it is recommended that you first read the “Multilevel Linear
Referencing Systems (MLRS)” section of the “Introduction to Linear Referencing” chapter
for a basic description of the GeoTrans Multilevel LRS data model. Also recommended is
the “Single Level to Multilevel LRS Conversion Workflow” chapter for help in initial
creation and population of a Multilevel LRS.
LRS Analysis Using a Multilevel LRS
In this section, topics pertaining to performing analysis with a Multilevel LRS are
examined. The topics to be explored are as follows:
• Intelligent LRS features
• Region IDs
• Event location stability
• Multiple LRM Support
• Temporal analysis
Intelligent LRS Features
Perhaps the key concept in using Multilevel LRSs is the role of intelligent LRS features.
These features are created using the Display LRM command (see the “Working with the
Display LRM Command” chapter) in conjunction with the LRS Metadata Definition
command (see the “Working with the LRS Metadata Definition command” chapter). The
LRS Metadata Definition command defines the tables that make up a Multilevel LRS and
which fields in those tables play which roles. The Display LRM command uses that
metadata to display an intelligent LRS feature class using the user’s selected
LRM/Geometry combination.
This intelligent LRS feature class can then be used in any command that asks for “LRS
Features.” The benefit is that intelligent LRS feature classes have extra information tagged
3-1
36. Working with GeoMedia Transportation Manager
to them so that all LRS Model information is automatically filled out when it is used in
LRS analysis.
Use the Display LRM command to create an intelligent LRS feature class.
Use Display LRM’s intelligent feature class with any command that asks for LRS features.
LRS model and properties are automatically filled in.
3-2
37. Introduction to Working with Multilevel LRSs
Region IDs
A second key concept is Region IDs. One of the options given in the LRS Metadata
Definition command (see the “Working with the LRS Metadata Definition Command”
chapter) is to define Region IDs. This is a way of subdividing your network into logical
units. This is usually done using political boundaries. As shown in the previous example,
the Display LRM command (see the “Working with the Display LRM Command”
chapter) allows you the option to filter your output by these region IDs. This provides a
convenient way to minimize the amount of data you are working with at any particular
time and thus to improve performance.
Region IDs are made even more useful by the ability to edit the Region settings of an
intelligent LRS feature. This is done as with any query using the Query Properties dialog
box. This means the Display LRM query does not have to be re-created as you move
around to work with one region to another. Also, due to the dynamic pipe architecture of
the GeoMedia products, queries based on this intelligent LRS feature class will update to
reflect the new region settings.
Region IDs can minimize the amount of data being used and can improve performance.
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38. Working with GeoMedia Transportation Manager
Region ID settings can be edited. Analyses based on the intelligent LRS feature will update.
Event Location Stability
The GeoTrans Multilevel LRS data model is designed to provide for event location
stability. This topic is introduced in the “Event Location Stability” section of the
“Introduction to Linear Referencing” chapter. This is an optional capability.
The basic principle is that route names, measures, and even geometric representations are
volatile in that they may change over time. Therefore we recommend that you convert
your event data’s location information to a non-volatile format. We refer to this non-
volatile format as a Datum based location reference.
LRM LRM
Linear
LRM LRM
Datum
LRM
LRM
The Linear Datum is the foundation of Intergraph’s MLRS.
3-4
39. Introduction to Working with Multilevel LRSs
This location format conversion is implemented via a method referred to as Event
Registration using the LRS Event Transform command. Simply choose the LRM to
Datum transform mode when using this command. For linear events, also choose any
attributes that you want to be proportioned in case events need to be split.
The LRS Event Transform command is used to perform Event Registration.
This is a one-time process. The resultant converted event feature class should be saved as
the permanent version of the event table. That’s it! Your data has been protected.
To simplify usage of this converted event data, the commands that use event data have
been modified to use either LRM based or Datum based event data. If all of your data is
converted to a Datum based location format, you can use all of your event data together.
So, for instance, guardrail data originally collected with one LRM can be analyzed versus
accident data originally calculated using another LRM using the LRS Event Overlay
command.
Event data that has been registered can be used directly with all of GeoMedia
Transportation’s commands that use event data.
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40. Working with GeoMedia Transportation Manager
Multiple LRM Support
Although Event registration to a Datum based location reference is the recommended way
to work with event data collected using various LRMs, it is not the only way. The LRS
Event Transform command can convert event data directly from one LRM to another.
Simply choose the LRM to LRM transform mode when using this command. For linear
events, also choose any attributes that you want to be proportioned in case events need to
be split. But note that by using this method, the benefits of event location stability are not
attained.
The LRS Event Transform command can convert event data between LRMs.
Temporal Analysis
The GeoMedia Transportation products are designed to be able to be used either with or
without GeoMedia Transaction Manager. One can reap almost all of the benefits of using a
Multilevel LRS without using GeoMedia Transaction Manager, with one exception. That
exception is temporal data capture and analysis. GeoMedia Transaction Manager gives
you the ability to model your network as it changes over time and then to use it for
analyses such as evaluating the cost/benefit of various roadway improvement strategies or
performing trend analysis for congestion, safety, and so on.
This subsection addresses temporal analysis. Temporal data capture is covered later in this
chapter. In depth coverage of setting up and using GeoMedia Transaction Manager is
covered in the Working with GeoMedia Transaction Manager document. This is only
meant as an overview.
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41. Introduction to Working with Multilevel LRSs
Regarding temporal analysis, there are two tools for reviewing data that represents a given
time or time period. The first tool uses a “Valid Time filter.” This can be set using the Set
Valid Time Options button on the Transaction Manager Settings dockable control, shown
below. Simply set the Valid Time filter date to the date you want to see, and all the
features in that connection will display the portion of your data that represents that date.
You can set which date you wish to view via the Transaction Manager Settings control.
The second tool is the Temporal Query command. This tools lets you pick a specific date
as did the Valid Time filter, but it also has the option to pick a time range. It has two other
differences. First, the Temporal Query command works on one feature class at a time as
opposed to an entire connection. Second it can be run multiple times. That means you
might want to show your road network as it was between 1995 and 2000 in one color and
between 2000 and 2005 in another.
The Temporal Query command can be used to see a given date or a time range
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42. Working with GeoMedia Transportation Manager
Maintaining a Multilevel LRS
In this section, topics pertaining to maintaining a Multilevel LRS are examined. The topics
to be explored are as follows:
• Temporality During Editing
• Intelligent Editing
• Interactive Multilevel LRS Conflation
• Bulk Multilevel LRS Conflation
• Calibration
• Validation
• Routing
• Production tables
Temporality During Editing
This subsection covers how to use GeoMedia Transaction Manager to capture real-world
history while you are editing. In-depth coverage of setting up and using GeoMedia
Transaction Manager is covered in the Working with GeoMedia Transaction Manager
document. This is only meant as an overview.
GeoMedia Transaction Manager is designed to do several things, two of which are very
pertinent to editing transportation networks. The first is long-term transactions. That
means that while you are editing, your revisions are invisible to the normal user up until
the point you have accepted them and are ready to reveal them to the general user
population. You also have the option to discard some or all of your revisions. This way
any “mistakes" can be made and caught before affecting general system users.
The second pertinent capability of GeoMedia Transaction Manager is capturing temporal
history. By default it captures transactional temporal history. This means you can see
what your database looked like at any point in time. However, much more important to
transportation users is the optional ability to capture real-world temporal history. This
means you can see the database’s representation of the world as it existed at any point in
time. It can also be used to capture future representations of the world.
Both of these capabilities are very easy to use. The basic workflow is as follows:
1. Create a Revision Set (start an editing session).
2. Edit as usual.
3. Commit or Discard your changes, and Retire your Revision Set.
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43. Introduction to Working with Multilevel LRSs
GeoMedia Transaction Manager is used for the first and third steps. The second step is the
topic of the rest of this chapter that follows this subsection. You can think of GeoMedia
Transaction manager as bookends that come just before and just after your normal editing.
The first step, creating a revision set, is very easy. Just use the New option of the Revision
Sets command. The New Revision Set dialog box, shown below, has several key parts.
The Name and Description entries can be whatever you want and are usually used to
describe the types of edits you are making. The Options section tells GeoMedia
Transaction Manager whether you are using Pessimistic or Optimistic transactions. A full
description of these choices is in the Working with GeoMedia Transaction Manager
document, but Pessimistic is the correct choice in most situations.
The Valid from date is the date that you want your edits to represent. So, for example, if
you are editing your network to show a curve realignment that went into service on
7/7/2003 and will stay in service indefinitely, you would fill out the dialog box as shown
below.
If you know the date your changes will go out of effect, then use an actual date for the
Valid until date as opposed to Valid until Modified. Lastly, but very importantly, if your
edits are to represent some real-world change, you would check Capture Valid Time for
Updates and Deletes, as shown here. However, if your edits are just to correct data, then
you would not check either of these. Note that Inserts are always stamped with the Valid
from/Valid until dates, so make sure to set these dates appropriately regardless of which
capture Valid Time options you choose.
The New Revision Set dialog sets the parameters for editing with GeoMedia Transaction
Manager.
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