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GIS in the Rockies
                          presents
Introduction to LiDAR



                                                               September 19, 2012


 Engineering | Architecture | Design-Build | Surveying | GeoSpatial Solutions
Presenter Bio


       Bruce Adey, GISP
       • LiDAR/Photogrammetry Discipline Lead
         (GeoSpatial Solutions, Merrick & Company)

       •    Geospatial professional since 1999


        Professional     experience includes working directly with
            Project Managers in developing schedules and budgets for
            current & future projects, supervising the production staff to
            ensure that the data collected and delivered meets or
            exceeds industry/client standards, and also technical
            support and development of MARS® software.

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Copyright © 2010 Merrick & Company All rights reserved.
Presenter Bio


       Mark Stucky, GISP

       •       MARS® Technical Support Specialist
               Senior GIS Analyst (GeoSpatial Solutions,
               Merrick & Company)

       •    Geospatial professional since 1990

       •    Professional experience includes MARS® software
            sales, licensing, design, testing, and technical support;
            ArcGIS geodatabase design, editing, and QC;
            extensive work with the FEMA DFIRM flood map
            modernization effort
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Copyright © 2010 Merrick & Company All rights reserved.
Corporate Overview
          Corporate headquarters: Aurora, Colorado
          Founded in 1955; employee-owned
          $115M annual revenue (FY11)
          ~ 500 employees at 10 national + 3 international offices
          Market Focus
                           Energy
                           Security
                           Life Sciences
                           Infrastructure
          Business                           Units
                           GeoSpatial Solutions          Civil Engineering Solutions
                           Military / Gov’t Facilities Fuels & Energy
                           Science & Technology          Nuclear Services & Technology
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Copyright © 2010 Merrick & Company All rights reserved.
Office Locations



            Aurora, CO
          (Headquarters)                                                         Ottawa, Canada

                                                                                 Washington, DC
       Colorado Springs, CO
                                                                             Charlotte, NC

                   Los Alamos, NM                                             Oak Ridge, TN

                                                                            Duluth, GA
                      Albuquerque, NM
                                                                            Atlanta, GA




                                                          San Antonio, TX

                Guadalajara, Mexico (MAPA)



                       Mexico City, Mexico (MAPA)




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Copyright © 2010 Merrick & Company All rights reserved.
Workshop Agenda
                                      Workshop                  Objectives
                                      LiDAR                Technology Review
                                      LiDAR                Applications
                                      Data               Processing Workflow
                                      Project              Data Deliverables
                                      <<<                15 minute Break >>>
                                      LiDAR                Data Demonstration
                                      Project              Planning (Airborne)
                                      LiDAR                QC
                                     Q           &A
                                      Online               Resources
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Copyright © 2010 Merrick & Company All rights reserved.
Workshop Objectives


          • Provide an objective and practical review of project
               requirements and technical information regarding
               airborne LiDAR data acquisition projects

          • Educate, communicate and evangelize the benefits of
               airborne remote sensing, especially as it pertains to
               LiDAR and the practical applications of laser
               scanning technologies

          • Informal conversation  feel free to ask questions!


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LiDAR Technology Overview




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What is LiDAR?

        LiDAR      (Light Detection And Ranging) is an active
            optical technology that uses pulses of laser light to
            strike the surface of the earth and measure the
            time of each pulse return to derive an accurate
            elevation.

        LiDAR                          data acquisition system includes:
             •     LiDAR sensor
             •     Digital camera(s)
             •     Airborne GPS
             •     IMU (Inertial Measurement Unit)
             •     Power Supply / Data Storage
             •     Pilot / Flight Operator
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Copyright © 2010 Merrick & Company All rights reserved.
LiDAR Data Acquisition




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Laser Scan Patterns

  Elliptical Pattern   Rotating Optical Pattern   Sinusoidal Pattern   Saw Tooth Pattern
  Used by the AHAB      Used by Riegl / TopoSys     Used by Leica        Used by Optech
DragonEye and TopEye




• Advantages and disadvantages with each scan pattern (ex.
  data uniformity, power consumption, duplicate points,
  accuracy along edge, field of view, etc.)
• Some LiDAR data will look different, based on the sensor
LiDAR Return Display
                                   First Returns          Second Returns




                                 Third Returns            Fourth Returns




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Profile View

            Cross-section view of trees, rendered by return values




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Advantages of LiDAR

         Accessibility:     LiDAR is a non-intrusive method to
              collect data in areas of limited, risky, or prohibited
              access

         Day      or Night: LiDAR data collection not limited to
              daylight hours

         Collection     Area: Large areas may be collected in a
              short timeframe (ex. 300 – 500 square miles per lift)

         Simultaneous     Collection: Shortens overall project
              schedules and reduces post-processing rectification
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Copyright © 2010 Merrick & Company All rights reserved.
Advantages of LiDAR

          Multiple    Collection Platforms: LiDAR can be collected
              from fixed-wing aircraft, helicopter, unmanned aerial
              vehicle (UAV), truck, train, tripod, etc.


          Canopy     Penetration: LiDAR can penetrate vegetation
              canopy to derive ground detail better than traditional
              photogrammetric approaches


          Better   Accuracy: LiDAR accuracy is much better in
              vegetation compared to traditional photogrammetric
              methods; ±10 cm horizontal, ±15 cm vertical

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Copyright © 2010 Merrick & Company All rights reserved.
Challenges of LiDAR

            Data     density increasing rapidly! Data volumes
                 growing exponentially!!


            Optimal      weather conditions necessary for data
                 collection


            Large      point cloud data sets are cumbersome to
                 store, manage, analyze and distribute


            Water                      / snow typically absorbs or scatters laser
                 pulses
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Copyright © 2010 Merrick & Company All rights reserved.
Common LiDAR Misconceptions
           LiDAR is a raster data product.
             False – LiDAR refers to a randomly distributed point cloud data set



           First return points are always canopy or last return points are always
            ground.
             False – First and last returns can either be ground or canopy


           ‘Middle’ return information is unnecessary.
                  False – Client should require that all returns (1 – 4) are present within
                   LiDAR data deliverables (raw and classified)


           LiDAR ≠ GIS  users Should Not (and cannot in most software) add,
            delete, or move LiDAR points!


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Data Acquisition Platforms




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Data Acquisition Platforms




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Copyright © 2010 Merrick & Company All rights reserved.
Airborne Systems
Fixed Wing
    Typical Altitude: 3,000’ – 12,000’ feet / 1,000 – 4,000 meters (AGL)
    Mainly used for large, wide-area collections
    1 – 8 points per square meter
    Common to collect LiDAR & digital imagery simultaneously


Rotary (Helicopter)
    Typical Altitude: 500’ – 2,500’ feet / 200 – 1,000 meters (AGL)
    Well-suited for narrow corridors (ex. utility, transportation) and small
     area, high-density collections
    10 – 1,000+ points per square meter!
    System may include digital cameras, video camera, meteorological
     sensors, thermal sensors, etc.
Airborne LiDAR – Fixed-Wing




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Airborne LiDAR - Helicopter




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Data Differences – Higher LiDAR Density
       Fixed-Wing LiDAR Example                           Helicopter LiDAR Example
                    Approx. 1 - 2 points / square meter     Approx. 20 - 30 points / square meter




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Mobile LiDAR – Road Corridor




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Terrestrial LiDAR – Electric Substation




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LiDAR Applications




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Floodplain Mapping / Inundation Modeling




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                                                          © 2010 URISA
Water Resources Modeling




  Sediment plume in wetlands from the creek, can’t see this from imagery or
PREXXXX 28 remotely derived elevation sources, heavy vegetation in the area
  other
Copyright © 2010 Merrick & Company All rights reserved.
Watershed Delineation


                         Streams (blue)
                        Catchments (red)
Transmission Line Mapping




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Utility Vegetation Management




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Transportation - Railroad




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                                                          © 2010 URISA
Land Cover Classification




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Land & Commercial Development




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Infrastructure




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Historic Preservation / Urban Planning
Geologic Mapping – Karst Study
3D Visualization - Planning
…More Applications…!!!
                       Homeland                           Security
                       Disaster  / Emergency Preparedness &
                           Response
                       Pipeline                          Mapping
                       Forensic                          Investigations
                       Conservation                          Management
                       Mining
                       Levee                     Recertification
                       Airfield                     Obstructions (Approach / Take-off)
                       Vegetation                          Mapping
                       Archaeology

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Copyright © 2010 Merrick & Company All rights reserved.
Data Processing Workflow




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Copyright © 2010 Merrick & Company All rights reserved.
Raw LiDAR
 LiDAR  is collected in a proprietary format, based on the
 sensor’s manufacturer. This data is typically referred to as
 “raw” (unprocessed) LiDAR point cloud data.


 Sensormanufacturers have their own post-processing
 software that combines raw scan data with GPS (position)
 data and IMU (orientation) data to produce a georeferenced
 LiDAR file (LAS).


 Atthis point, the point cloud data is “dumb” – no data
 classifications have been assigned; typically organized by
 individual flight lines
Post-Processing
 Coverage      Check
     Identifies data voids and verifies that LiDAR dataset covers the entire
      project extent

 Generate LAS files from hardware vendor’s post-processing
 software (i.e. merge GPS, IMU and LiDAR sensor inputs
 based on time)

 Validate    & adjust relative accuracy of adjacent flight lines
     Adjust flight line data for roll bias and/or other data collection issues

 Shift
      entire LiDAR point cloud to match ground control
 points
LAS File Format
 The LAS file format is an open, public file format for the
 interchange of 3D point cloud data between users (as
 defined by ASPRS)

 Developed by ASPRS in conjunction with LiDAR vendors
 and industry members of the ASPRS Standards Committee

 Binary   format (smaller); high performance (faster)


 http://www.asprs.org/society/committees/standards/LiDAR_
 exchange_format.html
Which LAS File Format?
        The    LAS file format and Point Data Record Format
            determine what information can be stored at the file level
            and point level
                     (e.g.; GPS time, RGB info, waveform data)


        Includes     all relevant LiDAR attributes  classification,
            intensity, return info, timestamp, flightline info, RGB values,
            etc.


        LAS                Versions 1.0, 1.1, 1.2, 1.3, 1.4, 2.0 (under review)



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Copyright © 2010 Merrick & Company All rights reserved.
LAS File (Header) Properties
LAS Point Properties
LiDAR Classification (aka Filtering)



                     LiDAR data classification is a filtering process
                       by which raw laser data is organized into
                        logical collections (i.e. data layers). The
                         filtering process is based on the point’s
                      attributes and geometric relationships of the
                                laser data in the point cloud.




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Copyright © 2010 Merrick & Company All rights reserved.
ASPRS LiDAR Data Classifications*
                   Classification Code                                Class
                                      0                    Created, never classified
                                      1                    Unclassified
                                      2                    Ground
                                      3                    Low Vegetation
                                      4                    Medium Vegetation
                                      5                    High Vegetation
                                      6                    Building
                                      7                    Low Point (Noise)
                                      8                    Model Keypoints
                                      9                    Water
                                      10                   Reserved for ASPRS Definition
                                      11                   Reserved for ASPRS Definition
                                      12                   Overlap Points
                                      13 - 31              Reserved for ASPRS Definition
                 *Source: LAS Specification, Version 1.2
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Copyright © 2010 Merrick & Company All rights reserved.
Point Cloud Classification

          The    LiDAR data classification value is the only point
              cloud attribute that can be modified


          The     number, name and description of the point cloud
              data classifications is project-specific and must be
              defined by the client


          Typical                        data classifications include:
                               1 = Unclassified, 2 and/or 8 = Ground, 3/4/5 = Vegetation,
                               6 = Buildings, 7 = Low Points / Noise, 9 = Water,
                               13 = Superseded (junk)


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Project Data Deliverables




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Project Data Deliverables

                     Raw,                   boresighted LiDAR (organized by flight line)
                     Classified,                          georeferenced, tiled LiDAR (LAS) data
                     Color                   Digital Orthophotography
                     Digital                   Elevation Model – DEM (grids)
                     Linear                    / polygonal breaklines (hydro-enforcement)
                     Digital                   Terrain Model – DTM
                     Elevation                           Contours (topography)
                     Tile              Scheme
                     Control                       Report
                     Project                      Metadata (FGDC-compliant)
                     Project                      Summary Report
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Derivative Surface Models


         DSM                                                 DTM




                                                            DTM,
                                                           showing
           DEM                                            breaklines




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Breaklines

 Definition:
            Linear vector features that describe an abrupt
 change in the elevation of the terrain which might affect
 contours, hydrology and other engineering models

 Natural   breaklines (hard):
     Ridge lines
     Toe of hill
     Edge of water body (ex. pond, lake) or stream

 Soft   (man-made) breaklines:
     Roads
     Retaining Walls
     Dams
Breaklines - Waterbodies
Elevation Contours (Topography)
15 minute Break
LiDAR Data Demonstration




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Copyright © 2010 Merrick & Company All rights reserved.
Project Planning
                                                          (Airborne)




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Project Objective?

            Understanding & communicating the project objective
            allows the vendor to properly scope the data collection
                   plan to meet stated project requirements!


        What                   is the purpose of this project?
                  We need updated elevation data for new floodplain
                   modeling program…
                  The county engineer requires updated terrain model for
                   storm water / surface water runoff and hydrologic
                   modeling…
                  The county assessor needs to update GIS system with
                   more accurate elevation data and generate new 2’
                   contours for the cadastral system…
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Copyright © 2010 Merrick & Company All rights reserved.
Project Specifications
 LiDAR    - Ground Sample Distance (GSD)
    Average distance between LiDAR points on the ground
    Can also be expressed in ‘points per square meter’ (PPSM)
    Example: One (1) meter GSD to support generation of 2’ contours

 LiDAR    - Vertical Accuracy
    Absolute accuracy of LiDAR points to known ground surface
    Example 1: ± One (1) foot vertical accuracy at 95% confidence
    Example 2: Root Mean Squared Error (RMSEZ) = 0.60 foot = 7.2
     inches

 Orthophotography       (pixel resolution)
    Example: One (1) foot orthophotos (typically georectified using
     LiDAR-derived surface model)
Point Density vs. Point Spacing
                      Point Density = 1 / Point Spacing2
                                   1 meter Point Spacing

                             1 meter                     1 meter


                                           1 meter
                             Point Density = 1 point / sq. meter

                                                           2 meter Point Spacing


 0.5 meter Point Spacing
                      0.5 meter           2 meters
1 meter
                                                                   2 meters
          0.5 meter
 Point Density = 4 points / sq. meter            Point Density = 0.25 points / sq. meter
Flight Plan Example


   LiDAR / Ortho Collection Parameters
              131.13 square miles
              34 flight lines; 389 flight miles
              1 meter GSD
              1’ foot color imagery
              13,500’ MSL / 5,930’ AGL
              34 flight lines; 2,516 photos
              12 flight hours
              18 photo control / control points
              100 knot flight speed



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Copyright © 2010 Merrick & Company All rights reserved.
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Copyright © 2010 Merrick & Company All rights reserved.
                                                          © 2010 URISA
‘Forgotten’ Project Issues
        Data                  Quality Control (QC)
              Who is responsible for verifying compliance to the project
               specifications?
              How will QC be completed?
              What tools are needed to perform comprehensive data QC?


        Hardware                               Resources
                  Data Storage - clients must plan to receive, manage, distribute
                   and store LiDAR, imagery, and other data deliverables
                                                      Examples: Classified LAS – 400 MB / mile2
                                                                ESRI raster grid (2-foot cell size) - 7 MB / mile2

                  PC workstations – do users have the proper PC equipment to
                   efficiently visualize, analyze, and process LiDAR deliverables?

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Copyright © 2010 Merrick & Company All rights reserved.
‘Forgotten’ Project Issues

        Human                         Resources

                  End-user training - clients should train & prepare employees on
                   basic LiDAR concepts prior to data delivery


                  Clients should obtain necessary LiDAR viewing/processing
                   software in advance to allow time for employees to learn to
                   properly exploit the data


                  For first-time projects, expect some “ramp-up” time as with any
                   new technology or software


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Copyright © 2010 Merrick & Company All rights reserved.
Other Challenges

            Optimal      weather conditions necessary for data
                 collection

            Leaf-off                         preferred for best ground penetration

            Ground      conditions - snow cover and standing
                 water/saturated ground typically absorb or scatter
                 laser pulses

            Nearest                           secure airport with necessary services (ex.
                 fuel)

            Accessibility                                and safety for the crew
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Copyright © 2010 Merrick & Company All rights reserved.
Keys to a Successful Project

 Understand your mapping requirements and the purpose for
 completing a LiDAR project.

 Utilize
      a qualification-based selection process to select your
 LiDAR consultant.

 Stayaway from low price bid projects! Price-based selection
 causes some firms to cut corners (ex. offshore labor) to
 lower project cost.

 Hire   a photogrammetric firm that owns a LiDAR sensor.

 Request    a quality control plan.
Keys to a Successful Project

 Dedicate the appropriate number of internal resources to
 the project.

 Know exactly how the quality control is going to be
 performed by the consultant and internally.

 Understand the differences in LiDAR technology. The age
 of the sensor determines capabilities; pulse rate, roll
 compensation, field of view are unique to each system.

 Determinewhich accuracy specification is going to be
 adhered to (i.e. ASPRS, NDEP, etc.)
Keys to a Successful Project

 Hybrid accuracy standards should only be used as long as
 there is very detailed metadata and documentation that
 clearly explain the accuracy results.


 Do   not exclude the ground truth surveying from a project.


 Request a LiDAR flight plan in the Request For
 Qualifications that clearly demonstrates the consultant’s
 understanding of the data acquisition issues.
Factors that Affect Price
        Size                 of Project Area
                  Area-of-Interest (AOI) size
                         Very small areas (< 50 square miles) tend to be more
                          expensive
                         Larger areas tend to cost less per square mile
                  AOI Shape – irregularly shaped AOIs may increase project cost

        Equipment                                   Mobilization (aka ‘mobe’)
                  Cost to move equipment & personnel to/from project area
                  Weather en route can cause delays
                  Vendors seek to ‘bundle’ work in same area to reduce
                   mobilization fees

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Copyright © 2010 Merrick & Company All rights reserved.
Factors that Affect Price

           Weather                             / Flying Conditions
                      Air traffic, inclement weather, dust, humidity affect ability to
                       acquire airborne data

           Platform                            Choice
                      Helicopter is much more expensive than fixed-wing


           Project                        Specifications (ex. GSD, accuracy, etc.)
                      More aggressive specifications usually cost more to deliver
                      Greater overlap or cross flights may be needed (vegetation)


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Factors that Affect Price

           Project                        Data Deliverables / Delivery Schedule

           Map                   Accuracy Specifications
                      ASPRS, FEMA, USGS…….select one!
                      Accuracy reporting specifications
                             Example: USGS - Fundamental Vertical Accuracy (FVA)


           Quality                        Control Process
                      Project & client specific – requires coordination



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LiDAR Quality Control




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QC Introduction

          Many      automated steps and mechanical devices
              that can cause systematic error

          Good    LiDAR companies understand both their
              procedures and equipment

          Knowing    sources of error can help prevent issues
              and check for them

          Known     mechanical / system error can often be
              corrected


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QC Recommendations

        Require     a QC plan & a report as part of the project
            deliverables!

       A     well-written quality control plan must be tailored to properly
            analyze data deliverables, especially as it relates to meeting /
            exceeding the project objective and vertical accuracy
            specifications

        QC     analysis must be quantifiable and representative of the
            entire data set

        Client   / end-users must have sufficient technical knowledge to
            understand QC results (and how issues can be mitigated!)

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True or False?




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Quality vs. Cost?
         Poor quality data is often the trade-off to push the price
         down

                    Data providers vary the procedure, frequency, and extent
                     of their LiDAR calibration

                    Less-skilled (cheaper) technicians and operators may
                     not recognize when problems, failures, and errors occur

                    Often times, little or no documented QA / QC procedures
                     to validate approach or allow for testing duplication

                    Vendor may not provide a summary report or ground
                     control report
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Quality vs. Cost?

                    Some vendors “cheat” to get around proper calibration and
                     other QC tasks


                           Clipping off or reclassifying edge lap to avoid dealing with LiDAR
                            boresight

                           Shifting tiles to a custom geoid (derived from the vertical error to
                            ground control)

                           Some vendors can hide error through other creative techniques
                            (especially if they discover problems after the plane has left the
                            project site!!!)




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Potential Sources of Error

        Planning

              Incorrect project boundary (missing buffer)
              Wrong horizontal and/or vertical datum
              Coordinate conversions & translations (ex. US foot
               vs. international survey foot)
              GSD inadequate to meet accuracy expectations
              Pulse rate not correct for desired flying altitude and
               vertical accuracy
              Field of view too wide for adequate penetration in
               vegetation
              Too small edge lap could cause data voids (missing
               data)
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Potential Sources of Error

        During the Mission

              Electrical problem or equipment failure (ground-based or
               airborne)
              System operator error
              Pilot error (not following flight plan)
              Weather and/or ground conditions


        Post-processing

              Incorrect boresighting
              Auto and manual classification (filtering)
              Poor breakline compilation
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Visual QC Approaches




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Flight Line Information
   • Flight line info allows for a quality control check to be performed in overlap areas
   • If a shift is detected within a flight line, this shift can be corrected if flight line
        information is present
   • You should request unique flight line information in your LiDAR dataset




       Unique flight line IDs. Flight line ID 4           Non-unique flight line IDs. Flight line ID
      (pink) is shifted +1 foot. Flight line ID 5         1 (green) is shifted +1 foot. Flight line ID
      (yellow) is not shifted. This data can be               1 (green) is not shifted. This data
                      corrected.                                    cannot be corrected.

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Other Visual QC Methods

          Viewing                             LiDAR points by classification values


          Overlaying                                     contours generated by flight line


          Comparing                              same X,Y location from adjacent flight
              lines (                          Z or flight line separation)


          Hillshade    analysis of ground classifications – “pits”
              and “spikes”

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Copyright © 2010 Merrick & Company All rights reserved.
Visual Hillshade Analysis (Ground)

          Allows     users to visually inspect the ground classification for
              anomalies. Quickly identifies the effectiveness of bare-earth
              extraction capabilities of the vendor.




                      Points rendered by data             Hillshade image of
                           classification                  the ground class
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Visual Analysis - Profile View




                                            Profile of Ground & Vegetation Classes




                                                          Profile of Ground Class
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Quantitative QC Approaches




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LAS File Statistics
       A simple method to analyze LiDAR data deliverables
       is to review the statistics of the point cloud.

                  Zmin & Zmax  provide insight into data filtering results
                  Point Density
                  Average Ground Sample Distance (GSD)
                  Return Information (1st, 2nd, 3rd, etc.)
                  Data Classifications – has the data been classified into
                   the specified classes?
                  Flightline information – is it present?
                  Statistics allow users to thematically map results in GIS
                   applications, which can help identify “problem” areas,
                   trends or data anomalies
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Copyright © 2010 Merrick & Company All rights reserved.
Control Report
        To    verify compliance to the project’s vertical accuracy
            specification, vendors compare ground control
            “checkpoints” to the derived ground classification /
            surface

        American      Society of Photogrammetry and Remote
            Sensing (ASPRS), National Map Accuracy Standards
            (NMAS) and National Standard for Spatial Data
            Accuracy (NSSDA) maintain their own vertical accuracy
            specifications

        Can     also be used to report the attainable accuracy of
            contours generated from smoothed, gridded LiDAR
            data
PREXXXX 88
Copyright © 2010 Merrick & Company All rights reserved.
USGS-NGP LiDAR Base Specification
                    Version 1.0




PREXXXX 89
Copyright © 2010 Merrick & Company All rights reserved.
Purpose and Scope
        USGS:      “The U.S. Geological Survey (USGS)
            intends to use this specification to acquire and
            procure light detection and ranging (lidar) data, and
            to create consistency across all USGS National
            Geospatial Program (NGP) and partner funded
            lidar collections, in particular those undertaken in
            support of the National Elevation Dataset (NED).”

        The    USGS specification is the basis for most of the
            American Recovery and Reinvestment Act (ARRA,
            2009) funded LiDAR projects in the U.S.; often used
            as a SOW document for many non-ARRA funded
            LiDAR projects
PREXXXX 90
Copyright © 2010 Merrick & Company All rights reserved.
USGS LiDAR Specification
        “Unlike most other “lidar data procurement specifications”,
            which are focused on the products derived from lidar point
            cloud data; such as the bare-earth Digital Elevation Model
            (DEM), this specification places unprecedented emphasis
            on the handling of the source lidar point cloud data.”

        Defines     minimum parameters for compliance; additional
            project upgrades listed (ex. increased vertical accuracy)

        Specification                                    divided into four (4) main sections:
                  Collection
                  Data Processing and Handling
                  Hydro-Flattening Requirements
                  Data Deliverables

PREXXXX 91
Copyright © 2010 Merrick & Company All rights reserved.
Collection Requirements
                          Returns                         (minimum of three)
                          Intensity                       values
                          Point                  Density / Nominal Point Spacing (NPS)
                          Data                  Voids
                          Spatial                        Distribution Verification
                          Scan                   Angle
                          Vertical                       Accuracy
                          Relative                        Accuracy
                          Flightline                       Overlap
                          Collection                        Area (coverage check)
                          Collection                        Conditions (weather)
PREXXXX 92
Copyright © 2010 Merrick & Company All rights reserved.
Data Processing & Handling Requirements

                                LAS                      Format (v1.2 or v1.3)
                                Waveform                       Data (*.wdp auxiliary files)
                                GPS                      Time Type
                                Datums                      (horizontal & vertical)
                                Projections
                                Units                    of Measure
                                File                Sizes
                                File                Source ID (unique per swath)


PREXXXX 93
Copyright © 2010 Merrick & Company All rights reserved.
Data Processing & Handling Requirements

                                  Point                  Families (return information)
                                  Swath                   Coverage
                                  Noise                   Classes & Withheld Points
                                  Overlap                   Points
                                  Positional                  Accuracy Validation
                                  Classification                 Accuracy / Consistency
                                  Tiles                  (orientation and overlap)



PREXXXX 94
Copyright © 2010 Merrick & Company All rights reserved.
Hydro-Flattening
                                                   Visual only – no automated testing yet




                LiDAR only – no breaklines                                      Hydro-Flattened
                defining water boundaries                                           LiDAR

PREXXXX 95
Copyright © 2010 Merrick & Company All rights reserved.
Other Standards




PREXXXX 96
Copyright © 2010 Merrick & Company All rights reserved.
Industry Accuracy Standards
          Guidelines    for Digital Elevation Data (released by the
              NDEP (National Digital Elevation Program.)
              Guidelines are available online at
              http://www.ndep.gov/NDEP_Elevation_Guidelines_Ver1
              _10May2004.pdf


          ASPRS       Guidelines Vertical Accuracy Reporting for
              LiDAR Data. Guidelines were subsequently adopted
              from NDEP, and are available online at
              http://www.asprs.org/society/committees/LIDAR/Downlo
              ads/Vertical_Accuracy_Reporting_for_LIDAR_Data.pdf



PREXXXX 97
Copyright © 2010 Merrick & Company All rights reserved.
Industry Accuracy Standards

          The     USGS (United States Geologic Survey) publishes
              an accuracy standard called the NMAS (National Map
              Accuracy Standard.) This document is available
              online at
              http://rockyweb.cr.usgs.gov/nmpstds/nmas.html


          The     FGDC (Federal Geographic Data Committee) is
              an interagency committee that created the NSSDA.
              This set of guidelines are available online at
              http://www.fgdc.gov/standards


PREXXXX 98
Copyright © 2010 Merrick & Company All rights reserved.
Questions?
Contact Information

 Bruce   Adey, GISP
         LiDAR/Photogrammetry Discipline Lead
    E-mail:   bruce.adey@merrick.com
    Direct:   (303) 353-3949



 Mark   A. Stucky, GISP
         MARS® Technical Support Specialist
         Senior GIS Analyst
    E-mail:   mark.stucky@merrick.com
    Direct:   (303) 353-3933


                       Thank You!
Online LiDAR Resources

 USGS-NGP          LiDAR Base Specification Version 1.0
    http://pubs.usgs.gov/tm/11b4/TM11-B4.pdf

 FEMA    Guidelines and Specifications for Flood Hazard
    Mapping Partners
    http://www.fema.gov/plan/prevent/fhm/gs_main.shtm

 ASPRS       LAS Specification
    http://www.asprs.org/society/committees/standards/lidar_exchange_f
    ormat.html

   USGS Center for LiDAR Information Coordination and
    Knowledge (CLICK)
    http://lidar.cr.usgs.gov/
Online LiDAR Resources

 International    LiDAR Mapping Forum (ILMF)
    http://www.lidarmap.org

   SPAR Point Group
    http://www.sparpointgroup.com/

   LiDAR News
    http://lidarnews.com/

   National LIDAR Dataset (USA)
    http://en.wikipedia.org/wiki/National_LIDAR_Dataset_-_USA

   USGS National Elevation Dataset (NED)
    http://ned.usgs.gov/

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2012 Workshop, Introduction to LiDAR Workshop, Bruce Adey and Mark Stucky (Merrick & Company)

  • 1. GIS in the Rockies presents Introduction to LiDAR September 19, 2012 Engineering | Architecture | Design-Build | Surveying | GeoSpatial Solutions
  • 2. Presenter Bio Bruce Adey, GISP • LiDAR/Photogrammetry Discipline Lead (GeoSpatial Solutions, Merrick & Company) • Geospatial professional since 1999  Professional experience includes working directly with Project Managers in developing schedules and budgets for current & future projects, supervising the production staff to ensure that the data collected and delivered meets or exceeds industry/client standards, and also technical support and development of MARS® software. PREXXXX 2 Copyright © 2010 Merrick & Company All rights reserved.
  • 3. Presenter Bio Mark Stucky, GISP • MARS® Technical Support Specialist Senior GIS Analyst (GeoSpatial Solutions, Merrick & Company) • Geospatial professional since 1990 • Professional experience includes MARS® software sales, licensing, design, testing, and technical support; ArcGIS geodatabase design, editing, and QC; extensive work with the FEMA DFIRM flood map modernization effort PREXXXX 3 Copyright © 2010 Merrick & Company All rights reserved.
  • 4. Corporate Overview  Corporate headquarters: Aurora, Colorado  Founded in 1955; employee-owned  $115M annual revenue (FY11)  ~ 500 employees at 10 national + 3 international offices  Market Focus  Energy  Security  Life Sciences  Infrastructure  Business Units  GeoSpatial Solutions Civil Engineering Solutions  Military / Gov’t Facilities Fuels & Energy  Science & Technology Nuclear Services & Technology PREXXXX 4 Copyright © 2010 Merrick & Company All rights reserved.
  • 5. Office Locations Aurora, CO (Headquarters) Ottawa, Canada Washington, DC Colorado Springs, CO Charlotte, NC Los Alamos, NM Oak Ridge, TN Duluth, GA Albuquerque, NM Atlanta, GA San Antonio, TX Guadalajara, Mexico (MAPA) Mexico City, Mexico (MAPA) PREXXXX 5 Copyright © 2010 Merrick & Company All rights reserved.
  • 6. Workshop Agenda  Workshop Objectives  LiDAR Technology Review  LiDAR Applications  Data Processing Workflow  Project Data Deliverables  <<< 15 minute Break >>>  LiDAR Data Demonstration  Project Planning (Airborne)  LiDAR QC Q &A  Online Resources PREXXXX 6 Copyright © 2010 Merrick & Company All rights reserved.
  • 7. Workshop Objectives • Provide an objective and practical review of project requirements and technical information regarding airborne LiDAR data acquisition projects • Educate, communicate and evangelize the benefits of airborne remote sensing, especially as it pertains to LiDAR and the practical applications of laser scanning technologies • Informal conversation  feel free to ask questions! PREXXXX 7 Copyright © 2010 Merrick & Company All rights reserved.
  • 8. LiDAR Technology Overview PREXXXX 8 Copyright © 2010 Merrick & Company All rights reserved.
  • 9. What is LiDAR?  LiDAR (Light Detection And Ranging) is an active optical technology that uses pulses of laser light to strike the surface of the earth and measure the time of each pulse return to derive an accurate elevation.  LiDAR data acquisition system includes: • LiDAR sensor • Digital camera(s) • Airborne GPS • IMU (Inertial Measurement Unit) • Power Supply / Data Storage • Pilot / Flight Operator PREXXXX 9 Copyright © 2010 Merrick & Company All rights reserved.
  • 10. LiDAR Data Acquisition PREXXXX 10 Copyright © 2010 Merrick & Company All rights reserved.
  • 11. Laser Scan Patterns Elliptical Pattern Rotating Optical Pattern Sinusoidal Pattern Saw Tooth Pattern Used by the AHAB Used by Riegl / TopoSys Used by Leica Used by Optech DragonEye and TopEye • Advantages and disadvantages with each scan pattern (ex. data uniformity, power consumption, duplicate points, accuracy along edge, field of view, etc.) • Some LiDAR data will look different, based on the sensor
  • 12. LiDAR Return Display First Returns Second Returns Third Returns Fourth Returns PREXXXX 12 Copyright © 2010 Merrick & Company All rights reserved.
  • 13. Profile View Cross-section view of trees, rendered by return values PREXXXX 13 Copyright © 2010 Merrick & Company All rights reserved.
  • 14. Advantages of LiDAR  Accessibility: LiDAR is a non-intrusive method to collect data in areas of limited, risky, or prohibited access  Day or Night: LiDAR data collection not limited to daylight hours  Collection Area: Large areas may be collected in a short timeframe (ex. 300 – 500 square miles per lift)  Simultaneous Collection: Shortens overall project schedules and reduces post-processing rectification PREXXXX 14 Copyright © 2010 Merrick & Company All rights reserved.
  • 15. Advantages of LiDAR  Multiple Collection Platforms: LiDAR can be collected from fixed-wing aircraft, helicopter, unmanned aerial vehicle (UAV), truck, train, tripod, etc.  Canopy Penetration: LiDAR can penetrate vegetation canopy to derive ground detail better than traditional photogrammetric approaches  Better Accuracy: LiDAR accuracy is much better in vegetation compared to traditional photogrammetric methods; ±10 cm horizontal, ±15 cm vertical PREXXXX 15 Copyright © 2010 Merrick & Company All rights reserved.
  • 16. Challenges of LiDAR  Data density increasing rapidly! Data volumes growing exponentially!!  Optimal weather conditions necessary for data collection  Large point cloud data sets are cumbersome to store, manage, analyze and distribute  Water / snow typically absorbs or scatters laser pulses PREXXXX 16 Copyright © 2010 Merrick & Company All rights reserved.
  • 17. Common LiDAR Misconceptions  LiDAR is a raster data product.  False – LiDAR refers to a randomly distributed point cloud data set  First return points are always canopy or last return points are always ground.  False – First and last returns can either be ground or canopy  ‘Middle’ return information is unnecessary.  False – Client should require that all returns (1 – 4) are present within LiDAR data deliverables (raw and classified)  LiDAR ≠ GIS  users Should Not (and cannot in most software) add, delete, or move LiDAR points! PREXXXX 17 Copyright © 2010 Merrick & Company All rights reserved.
  • 18. Data Acquisition Platforms PREXXXX 18 Copyright © 2010 Merrick & Company All rights reserved.
  • 19. Data Acquisition Platforms PREXXXX 19 Copyright © 2010 Merrick & Company All rights reserved.
  • 20. Airborne Systems Fixed Wing  Typical Altitude: 3,000’ – 12,000’ feet / 1,000 – 4,000 meters (AGL)  Mainly used for large, wide-area collections  1 – 8 points per square meter  Common to collect LiDAR & digital imagery simultaneously Rotary (Helicopter)  Typical Altitude: 500’ – 2,500’ feet / 200 – 1,000 meters (AGL)  Well-suited for narrow corridors (ex. utility, transportation) and small area, high-density collections  10 – 1,000+ points per square meter!  System may include digital cameras, video camera, meteorological sensors, thermal sensors, etc.
  • 21. Airborne LiDAR – Fixed-Wing PREXXXX 21 Copyright © 2010 Merrick & Company All rights reserved.
  • 22. Airborne LiDAR - Helicopter PREXXXX 22 Copyright © 2010 Merrick & Company All rights reserved.
  • 23. Data Differences – Higher LiDAR Density Fixed-Wing LiDAR Example Helicopter LiDAR Example Approx. 1 - 2 points / square meter Approx. 20 - 30 points / square meter PREXXXX 23 Copyright © 2010 Merrick & Company All rights reserved.
  • 24. Mobile LiDAR – Road Corridor PREXXXX 24 Copyright © 2010 Merrick & Company All rights reserved.
  • 25. Terrestrial LiDAR – Electric Substation PREXXXX 25 Copyright © 2010 Merrick & Company All rights reserved.
  • 26. LiDAR Applications PREXXXX 26 Copyright © 2010 Merrick & Company All rights reserved.
  • 27. Floodplain Mapping / Inundation Modeling PREXXXX 27 Copyright © 2010 Merrick & Company All rights reserved. © 2010 URISA
  • 28. Water Resources Modeling Sediment plume in wetlands from the creek, can’t see this from imagery or PREXXXX 28 remotely derived elevation sources, heavy vegetation in the area other Copyright © 2010 Merrick & Company All rights reserved.
  • 29. Watershed Delineation Streams (blue) Catchments (red)
  • 30. Transmission Line Mapping PREXXXX 30 Copyright © 2010 Merrick & Company All rights reserved.
  • 31. Utility Vegetation Management PREXXXX 31 Copyright © 2010 Merrick & Company All rights reserved.
  • 32. Transportation - Railroad PREXXXX 32 Copyright © 2010 Merrick & Company All rights reserved. © 2010 URISA
  • 33. Land Cover Classification PREXXXX 33 Copyright © 2010 Merrick & Company All rights reserved.
  • 34. Land & Commercial Development PREXXXX 34 Copyright © 2010 Merrick & Company All rights reserved.
  • 35. Infrastructure PREXXXX 35 Copyright © 2010 Merrick & Company All rights reserved.
  • 36. Historic Preservation / Urban Planning
  • 37. Geologic Mapping – Karst Study
  • 38. 3D Visualization - Planning
  • 39. …More Applications…!!!  Homeland Security  Disaster / Emergency Preparedness & Response  Pipeline Mapping  Forensic Investigations  Conservation Management  Mining  Levee Recertification  Airfield Obstructions (Approach / Take-off)  Vegetation Mapping  Archaeology PREXXXX 39 Copyright © 2010 Merrick & Company All rights reserved.
  • 40. Data Processing Workflow PREXXXX 40 Copyright © 2010 Merrick & Company All rights reserved.
  • 41. Raw LiDAR  LiDAR is collected in a proprietary format, based on the sensor’s manufacturer. This data is typically referred to as “raw” (unprocessed) LiDAR point cloud data.  Sensormanufacturers have their own post-processing software that combines raw scan data with GPS (position) data and IMU (orientation) data to produce a georeferenced LiDAR file (LAS).  Atthis point, the point cloud data is “dumb” – no data classifications have been assigned; typically organized by individual flight lines
  • 42. Post-Processing  Coverage Check  Identifies data voids and verifies that LiDAR dataset covers the entire project extent  Generate LAS files from hardware vendor’s post-processing software (i.e. merge GPS, IMU and LiDAR sensor inputs based on time)  Validate & adjust relative accuracy of adjacent flight lines  Adjust flight line data for roll bias and/or other data collection issues  Shift entire LiDAR point cloud to match ground control points
  • 43. LAS File Format  The LAS file format is an open, public file format for the interchange of 3D point cloud data between users (as defined by ASPRS)  Developed by ASPRS in conjunction with LiDAR vendors and industry members of the ASPRS Standards Committee  Binary format (smaller); high performance (faster) http://www.asprs.org/society/committees/standards/LiDAR_ exchange_format.html
  • 44. Which LAS File Format?  The LAS file format and Point Data Record Format determine what information can be stored at the file level and point level (e.g.; GPS time, RGB info, waveform data)  Includes all relevant LiDAR attributes  classification, intensity, return info, timestamp, flightline info, RGB values, etc.  LAS Versions 1.0, 1.1, 1.2, 1.3, 1.4, 2.0 (under review) PREXXXX 44 Copyright © 2010 Merrick & Company All rights reserved.
  • 45. LAS File (Header) Properties
  • 47. LiDAR Classification (aka Filtering) LiDAR data classification is a filtering process by which raw laser data is organized into logical collections (i.e. data layers). The filtering process is based on the point’s attributes and geometric relationships of the laser data in the point cloud. PREXXXX 47 Copyright © 2010 Merrick & Company All rights reserved.
  • 48. ASPRS LiDAR Data Classifications* Classification Code Class 0 Created, never classified 1 Unclassified 2 Ground 3 Low Vegetation 4 Medium Vegetation 5 High Vegetation 6 Building 7 Low Point (Noise) 8 Model Keypoints 9 Water 10 Reserved for ASPRS Definition 11 Reserved for ASPRS Definition 12 Overlap Points 13 - 31 Reserved for ASPRS Definition *Source: LAS Specification, Version 1.2 PREXXXX 48 Copyright © 2010 Merrick & Company All rights reserved.
  • 49. Point Cloud Classification  The LiDAR data classification value is the only point cloud attribute that can be modified  The number, name and description of the point cloud data classifications is project-specific and must be defined by the client  Typical data classifications include: 1 = Unclassified, 2 and/or 8 = Ground, 3/4/5 = Vegetation, 6 = Buildings, 7 = Low Points / Noise, 9 = Water, 13 = Superseded (junk) PREXXXX 49 Copyright © 2010 Merrick & Company All rights reserved.
  • 50. Project Data Deliverables PREXXXX 50 Copyright © 2010 Merrick & Company All rights reserved.
  • 51. Project Data Deliverables  Raw, boresighted LiDAR (organized by flight line)  Classified, georeferenced, tiled LiDAR (LAS) data  Color Digital Orthophotography  Digital Elevation Model – DEM (grids)  Linear / polygonal breaklines (hydro-enforcement)  Digital Terrain Model – DTM  Elevation Contours (topography)  Tile Scheme  Control Report  Project Metadata (FGDC-compliant)  Project Summary Report PREXXXX 51 Copyright © 2010 Merrick & Company All rights reserved.
  • 52. Derivative Surface Models DSM DTM DTM, showing DEM breaklines PREXXXX 52 Copyright © 2010 Merrick & Company All rights reserved.
  • 53. Breaklines  Definition: Linear vector features that describe an abrupt change in the elevation of the terrain which might affect contours, hydrology and other engineering models  Natural breaklines (hard):  Ridge lines  Toe of hill  Edge of water body (ex. pond, lake) or stream  Soft (man-made) breaklines:  Roads  Retaining Walls  Dams
  • 57. LiDAR Data Demonstration PREXXXX 57 Copyright © 2010 Merrick & Company All rights reserved.
  • 58. Project Planning (Airborne) PREXXXX 58 Copyright © 2010 Merrick & Company All rights reserved.
  • 59. Project Objective? Understanding & communicating the project objective allows the vendor to properly scope the data collection plan to meet stated project requirements!  What is the purpose of this project?  We need updated elevation data for new floodplain modeling program…  The county engineer requires updated terrain model for storm water / surface water runoff and hydrologic modeling…  The county assessor needs to update GIS system with more accurate elevation data and generate new 2’ contours for the cadastral system… PREXXXX 59 Copyright © 2010 Merrick & Company All rights reserved.
  • 60. Project Specifications  LiDAR - Ground Sample Distance (GSD)  Average distance between LiDAR points on the ground  Can also be expressed in ‘points per square meter’ (PPSM)  Example: One (1) meter GSD to support generation of 2’ contours  LiDAR - Vertical Accuracy  Absolute accuracy of LiDAR points to known ground surface  Example 1: ± One (1) foot vertical accuracy at 95% confidence  Example 2: Root Mean Squared Error (RMSEZ) = 0.60 foot = 7.2 inches  Orthophotography (pixel resolution)  Example: One (1) foot orthophotos (typically georectified using LiDAR-derived surface model)
  • 61. Point Density vs. Point Spacing Point Density = 1 / Point Spacing2 1 meter Point Spacing 1 meter 1 meter 1 meter Point Density = 1 point / sq. meter 2 meter Point Spacing 0.5 meter Point Spacing 0.5 meter 2 meters 1 meter 2 meters 0.5 meter Point Density = 4 points / sq. meter Point Density = 0.25 points / sq. meter
  • 62. Flight Plan Example LiDAR / Ortho Collection Parameters  131.13 square miles  34 flight lines; 389 flight miles  1 meter GSD  1’ foot color imagery  13,500’ MSL / 5,930’ AGL  34 flight lines; 2,516 photos  12 flight hours  18 photo control / control points  100 knot flight speed PREXXXX 62 Copyright © 2010 Merrick & Company All rights reserved.
  • 63. PREXXXX 63 Copyright © 2010 Merrick & Company All rights reserved. © 2010 URISA
  • 64. ‘Forgotten’ Project Issues  Data Quality Control (QC)  Who is responsible for verifying compliance to the project specifications?  How will QC be completed?  What tools are needed to perform comprehensive data QC?  Hardware Resources  Data Storage - clients must plan to receive, manage, distribute and store LiDAR, imagery, and other data deliverables Examples: Classified LAS – 400 MB / mile2 ESRI raster grid (2-foot cell size) - 7 MB / mile2  PC workstations – do users have the proper PC equipment to efficiently visualize, analyze, and process LiDAR deliverables? PREXXXX 64 Copyright © 2010 Merrick & Company All rights reserved.
  • 65. ‘Forgotten’ Project Issues  Human Resources  End-user training - clients should train & prepare employees on basic LiDAR concepts prior to data delivery  Clients should obtain necessary LiDAR viewing/processing software in advance to allow time for employees to learn to properly exploit the data  For first-time projects, expect some “ramp-up” time as with any new technology or software PREXXXX 65 Copyright © 2010 Merrick & Company All rights reserved.
  • 66. Other Challenges  Optimal weather conditions necessary for data collection  Leaf-off preferred for best ground penetration  Ground conditions - snow cover and standing water/saturated ground typically absorb or scatter laser pulses  Nearest secure airport with necessary services (ex. fuel)  Accessibility and safety for the crew PREXXXX 66 Copyright © 2010 Merrick & Company All rights reserved.
  • 67. Keys to a Successful Project  Understand your mapping requirements and the purpose for completing a LiDAR project.  Utilize a qualification-based selection process to select your LiDAR consultant.  Stayaway from low price bid projects! Price-based selection causes some firms to cut corners (ex. offshore labor) to lower project cost.  Hire a photogrammetric firm that owns a LiDAR sensor.  Request a quality control plan.
  • 68. Keys to a Successful Project  Dedicate the appropriate number of internal resources to the project.  Know exactly how the quality control is going to be performed by the consultant and internally.  Understand the differences in LiDAR technology. The age of the sensor determines capabilities; pulse rate, roll compensation, field of view are unique to each system.  Determinewhich accuracy specification is going to be adhered to (i.e. ASPRS, NDEP, etc.)
  • 69. Keys to a Successful Project  Hybrid accuracy standards should only be used as long as there is very detailed metadata and documentation that clearly explain the accuracy results.  Do not exclude the ground truth surveying from a project.  Request a LiDAR flight plan in the Request For Qualifications that clearly demonstrates the consultant’s understanding of the data acquisition issues.
  • 70. Factors that Affect Price  Size of Project Area  Area-of-Interest (AOI) size  Very small areas (< 50 square miles) tend to be more expensive  Larger areas tend to cost less per square mile  AOI Shape – irregularly shaped AOIs may increase project cost  Equipment Mobilization (aka ‘mobe’)  Cost to move equipment & personnel to/from project area  Weather en route can cause delays  Vendors seek to ‘bundle’ work in same area to reduce mobilization fees PREXXXX 70 Copyright © 2010 Merrick & Company All rights reserved.
  • 71. Factors that Affect Price  Weather / Flying Conditions  Air traffic, inclement weather, dust, humidity affect ability to acquire airborne data  Platform Choice  Helicopter is much more expensive than fixed-wing  Project Specifications (ex. GSD, accuracy, etc.)  More aggressive specifications usually cost more to deliver  Greater overlap or cross flights may be needed (vegetation) PREXXXX 71 Copyright © 2010 Merrick & Company All rights reserved.
  • 72. Factors that Affect Price  Project Data Deliverables / Delivery Schedule  Map Accuracy Specifications  ASPRS, FEMA, USGS…….select one!  Accuracy reporting specifications  Example: USGS - Fundamental Vertical Accuracy (FVA)  Quality Control Process  Project & client specific – requires coordination PREXXXX 72 Copyright © 2010 Merrick & Company All rights reserved.
  • 73. LiDAR Quality Control PREXXXX 73 Copyright © 2010 Merrick & Company All rights reserved.
  • 74. QC Introduction  Many automated steps and mechanical devices that can cause systematic error  Good LiDAR companies understand both their procedures and equipment  Knowing sources of error can help prevent issues and check for them  Known mechanical / system error can often be corrected PREXXXX 74 Copyright © 2010 Merrick & Company All rights reserved.
  • 75. QC Recommendations  Require a QC plan & a report as part of the project deliverables! A well-written quality control plan must be tailored to properly analyze data deliverables, especially as it relates to meeting / exceeding the project objective and vertical accuracy specifications  QC analysis must be quantifiable and representative of the entire data set  Client / end-users must have sufficient technical knowledge to understand QC results (and how issues can be mitigated!) PREXXXX 75 Copyright © 2010 Merrick & Company All rights reserved.
  • 76. True or False? PREXXXX 76 Copyright © 2010 Merrick & Company All rights reserved.
  • 77. Quality vs. Cost? Poor quality data is often the trade-off to push the price down  Data providers vary the procedure, frequency, and extent of their LiDAR calibration  Less-skilled (cheaper) technicians and operators may not recognize when problems, failures, and errors occur  Often times, little or no documented QA / QC procedures to validate approach or allow for testing duplication  Vendor may not provide a summary report or ground control report PREXXXX 77 Copyright © 2010 Merrick & Company All rights reserved.
  • 78. Quality vs. Cost?  Some vendors “cheat” to get around proper calibration and other QC tasks  Clipping off or reclassifying edge lap to avoid dealing with LiDAR boresight  Shifting tiles to a custom geoid (derived from the vertical error to ground control)  Some vendors can hide error through other creative techniques (especially if they discover problems after the plane has left the project site!!!) PREXXXX 78 Copyright © 2010 Merrick & Company All rights reserved.
  • 79. Potential Sources of Error Planning  Incorrect project boundary (missing buffer)  Wrong horizontal and/or vertical datum  Coordinate conversions & translations (ex. US foot vs. international survey foot)  GSD inadequate to meet accuracy expectations  Pulse rate not correct for desired flying altitude and vertical accuracy  Field of view too wide for adequate penetration in vegetation  Too small edge lap could cause data voids (missing data) PREXXXX 79 Copyright © 2010 Merrick & Company All rights reserved.
  • 80. Potential Sources of Error During the Mission  Electrical problem or equipment failure (ground-based or airborne)  System operator error  Pilot error (not following flight plan)  Weather and/or ground conditions Post-processing  Incorrect boresighting  Auto and manual classification (filtering)  Poor breakline compilation PREXXXX 80 Copyright © 2010 Merrick & Company All rights reserved.
  • 81. Visual QC Approaches PREXXXX 81 Copyright © 2010 Merrick & Company All rights reserved.
  • 82. Flight Line Information • Flight line info allows for a quality control check to be performed in overlap areas • If a shift is detected within a flight line, this shift can be corrected if flight line information is present • You should request unique flight line information in your LiDAR dataset Unique flight line IDs. Flight line ID 4 Non-unique flight line IDs. Flight line ID (pink) is shifted +1 foot. Flight line ID 5 1 (green) is shifted +1 foot. Flight line ID (yellow) is not shifted. This data can be 1 (green) is not shifted. This data corrected. cannot be corrected. PREXXXX 82 Copyright © 2010 Merrick & Company All rights reserved.
  • 83. Other Visual QC Methods  Viewing LiDAR points by classification values  Overlaying contours generated by flight line  Comparing same X,Y location from adjacent flight lines ( Z or flight line separation)  Hillshade analysis of ground classifications – “pits” and “spikes” PREXXXX 83 Copyright © 2010 Merrick & Company All rights reserved.
  • 84. Visual Hillshade Analysis (Ground)  Allows users to visually inspect the ground classification for anomalies. Quickly identifies the effectiveness of bare-earth extraction capabilities of the vendor. Points rendered by data Hillshade image of classification the ground class PREXXXX 84 Copyright © 2010 Merrick & Company All rights reserved.
  • 85. Visual Analysis - Profile View Profile of Ground & Vegetation Classes Profile of Ground Class PREXXXX 85 Copyright © 2010 Merrick & Company All rights reserved.
  • 86. Quantitative QC Approaches PREXXXX 86 Copyright © 2010 Merrick & Company All rights reserved.
  • 87. LAS File Statistics A simple method to analyze LiDAR data deliverables is to review the statistics of the point cloud.  Zmin & Zmax  provide insight into data filtering results  Point Density  Average Ground Sample Distance (GSD)  Return Information (1st, 2nd, 3rd, etc.)  Data Classifications – has the data been classified into the specified classes?  Flightline information – is it present?  Statistics allow users to thematically map results in GIS applications, which can help identify “problem” areas, trends or data anomalies PREXXXX 87 Copyright © 2010 Merrick & Company All rights reserved.
  • 88. Control Report  To verify compliance to the project’s vertical accuracy specification, vendors compare ground control “checkpoints” to the derived ground classification / surface  American Society of Photogrammetry and Remote Sensing (ASPRS), National Map Accuracy Standards (NMAS) and National Standard for Spatial Data Accuracy (NSSDA) maintain their own vertical accuracy specifications  Can also be used to report the attainable accuracy of contours generated from smoothed, gridded LiDAR data PREXXXX 88 Copyright © 2010 Merrick & Company All rights reserved.
  • 89. USGS-NGP LiDAR Base Specification Version 1.0 PREXXXX 89 Copyright © 2010 Merrick & Company All rights reserved.
  • 90. Purpose and Scope  USGS: “The U.S. Geological Survey (USGS) intends to use this specification to acquire and procure light detection and ranging (lidar) data, and to create consistency across all USGS National Geospatial Program (NGP) and partner funded lidar collections, in particular those undertaken in support of the National Elevation Dataset (NED).”  The USGS specification is the basis for most of the American Recovery and Reinvestment Act (ARRA, 2009) funded LiDAR projects in the U.S.; often used as a SOW document for many non-ARRA funded LiDAR projects PREXXXX 90 Copyright © 2010 Merrick & Company All rights reserved.
  • 91. USGS LiDAR Specification  “Unlike most other “lidar data procurement specifications”, which are focused on the products derived from lidar point cloud data; such as the bare-earth Digital Elevation Model (DEM), this specification places unprecedented emphasis on the handling of the source lidar point cloud data.”  Defines minimum parameters for compliance; additional project upgrades listed (ex. increased vertical accuracy)  Specification divided into four (4) main sections:  Collection  Data Processing and Handling  Hydro-Flattening Requirements  Data Deliverables PREXXXX 91 Copyright © 2010 Merrick & Company All rights reserved.
  • 92. Collection Requirements  Returns (minimum of three)  Intensity values  Point Density / Nominal Point Spacing (NPS)  Data Voids  Spatial Distribution Verification  Scan Angle  Vertical Accuracy  Relative Accuracy  Flightline Overlap  Collection Area (coverage check)  Collection Conditions (weather) PREXXXX 92 Copyright © 2010 Merrick & Company All rights reserved.
  • 93. Data Processing & Handling Requirements  LAS Format (v1.2 or v1.3)  Waveform Data (*.wdp auxiliary files)  GPS Time Type  Datums (horizontal & vertical)  Projections  Units of Measure  File Sizes  File Source ID (unique per swath) PREXXXX 93 Copyright © 2010 Merrick & Company All rights reserved.
  • 94. Data Processing & Handling Requirements  Point Families (return information)  Swath Coverage  Noise Classes & Withheld Points  Overlap Points  Positional Accuracy Validation  Classification Accuracy / Consistency  Tiles (orientation and overlap) PREXXXX 94 Copyright © 2010 Merrick & Company All rights reserved.
  • 95. Hydro-Flattening Visual only – no automated testing yet LiDAR only – no breaklines Hydro-Flattened defining water boundaries LiDAR PREXXXX 95 Copyright © 2010 Merrick & Company All rights reserved.
  • 96. Other Standards PREXXXX 96 Copyright © 2010 Merrick & Company All rights reserved.
  • 97. Industry Accuracy Standards  Guidelines for Digital Elevation Data (released by the NDEP (National Digital Elevation Program.) Guidelines are available online at http://www.ndep.gov/NDEP_Elevation_Guidelines_Ver1 _10May2004.pdf  ASPRS Guidelines Vertical Accuracy Reporting for LiDAR Data. Guidelines were subsequently adopted from NDEP, and are available online at http://www.asprs.org/society/committees/LIDAR/Downlo ads/Vertical_Accuracy_Reporting_for_LIDAR_Data.pdf PREXXXX 97 Copyright © 2010 Merrick & Company All rights reserved.
  • 98. Industry Accuracy Standards  The USGS (United States Geologic Survey) publishes an accuracy standard called the NMAS (National Map Accuracy Standard.) This document is available online at http://rockyweb.cr.usgs.gov/nmpstds/nmas.html  The FGDC (Federal Geographic Data Committee) is an interagency committee that created the NSSDA. This set of guidelines are available online at http://www.fgdc.gov/standards PREXXXX 98 Copyright © 2010 Merrick & Company All rights reserved.
  • 100. Contact Information  Bruce Adey, GISP LiDAR/Photogrammetry Discipline Lead  E-mail: bruce.adey@merrick.com  Direct: (303) 353-3949  Mark A. Stucky, GISP MARS® Technical Support Specialist Senior GIS Analyst  E-mail: mark.stucky@merrick.com  Direct: (303) 353-3933 Thank You!
  • 101. Online LiDAR Resources  USGS-NGP LiDAR Base Specification Version 1.0 http://pubs.usgs.gov/tm/11b4/TM11-B4.pdf  FEMA Guidelines and Specifications for Flood Hazard Mapping Partners http://www.fema.gov/plan/prevent/fhm/gs_main.shtm  ASPRS LAS Specification http://www.asprs.org/society/committees/standards/lidar_exchange_f ormat.html  USGS Center for LiDAR Information Coordination and Knowledge (CLICK) http://lidar.cr.usgs.gov/
  • 102. Online LiDAR Resources  International LiDAR Mapping Forum (ILMF) http://www.lidarmap.org  SPAR Point Group http://www.sparpointgroup.com/  LiDAR News http://lidarnews.com/  National LIDAR Dataset (USA) http://en.wikipedia.org/wiki/National_LIDAR_Dataset_-_USA  USGS National Elevation Dataset (NED) http://ned.usgs.gov/