Presented by Don Ferguson at 2012 WVAGP Membership Meeting.

1. Geospatial Modeling for the Optimization
of Search and Rescue Strategies
Don Ferguson, PhD
Mountaineer Area Rescue Group
A member of
Appalachian Search and Rescue Conference
WVAGP Membership Meeting
November 27, 2012
Sutton, WV
Appalachian Search and Rescue Mountaineer Area Rescue Group
Conference

2. Where Do We Start Looking?
 “Search” for a missing subject could
be considered the proverbial “needle
in a haystack”
Time is limited - Search is an emergency
Subject may be injured / will not survive
indefinitely
Clues deteriorate over time
Weather
Improve PSR by
Availability of resources
reducing the
 Goal of search management is to search area
maximize the probability of success at
the greatest rate possible.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

3. Improving the Success Rate
 Majority of searches are resolved within a few hours
Only about 1% – 3% required Extended Planning of
operations
 Extended searches typically encompass relatively
large geographical areas
 Two options for improving the Success Rate
Reduce the search area
Search in most likely areas first
Increase the rate of detection
Proper resource allocation
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

4. Application of Operational Research to SAR
 Need a systematic method to prioritize regions within the
search area and evaluate progress.
SAR operations typically time and resource limited
 OR provides framework to aid in decision-making and
improve efficiency.
Developed during WWII to search for enemy submarines and
improve resource allocation1
Bayesian Probability Theory
Assigning a probability to a hypothesis and adjusting the probability
through testing without needing to fully resolving the hypothesis
a1, a2, …, ak are mutually exclusive events
(hypothesis), of which none has a zero probability.
b is any event (data used to test the hypothesis).
1. Koopman, B.O., “Search and Screening: General Principles with Historical
Applications”, Pergamon Press, New York, 1980., 2003.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

5. Defining the Search Area
 Search area is defined by a
collection of methodologies
Theoretical
Distance traveled
Historical/Categorical mobility
data
Statistical
Historical/categorical search
25%
data 50%
Subjective-Deductive 75%
Subject and environment
specific Autistic
Distance from IPP (km)
Theoretical and
n 20 Statistical Search
25% 0.6 Area
50% 1.6 ISRID Data
75% 3.7
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group
95% 15.2

6. Theoretical Search Area
This is the distance that the subject could have
traveled in the time elapsed. How far, how fast?
Subject can theoretically travel in any direction
3.14 * (1mile)2 = 3.14miles2
Identifying a clue or DOT
could help to limit the
search area 10 mile radius
Could also alter
theoretical distance
by considering terrain
and environmental
impedance
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

7. Theoretical Search Area…cont
Cost Surface
- High slope impassable
- Reclassify NLCD Travel Time
- Roads, Trails, Streams, Hours
Utilities, Fenceline, 1
Water bodies 2
3-4
5-6
7-8
9 - 10
11 - 12
13
Tobler, W. 1993. Three presentations on geographical analysis and
modeling. Technical report. 93-1, National center for geographic information
and Analysis, University of California, Santa Barbara.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

8. Subjective / Deductive Area
 Formulate a series of hypotheses based on all available information
(geospatial, subject profile, etc).
 Compare hypotheses to determine most likely scenario (Analysis of
Competing Hypotheses)
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

9. Subjective / Deductive Area: Probability Regions
 A Region is a defined subset of the
Search Area within which there is a
uniform distribution of the likelihood of
containing the search object1 –
Probability of Containment (POC)
 Assign “a priori” probability of the
subject being in a location
 Based on scenarios comprised of
Theoretical Search Area
Statistical Search Area
Surrounding geography
Natural and man-made features
Physical and Behavioral profiles of the
missing subject
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

10. Develop Searchable Segments
 Sub-divisions of Probability Regions based on
logistical and operational issues associated with
conducting the search itself
Resource capabilities / availability
Well defined field recognizable
boundaries
 Segment POC
Area-weighted POC associated
with the Region POC.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

11. Tracking Success
 Segments are assigned based on POC with most
likely locations being searched first.
 Goal is to reduce (minimize) the
POC of a segment to zero
Hopefully locate the subject sooner
 Update POC after search of
each segment
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

12. Statistical Search Area
 Statistical data from previous searches involving
persons that could be considered categorically
similar could provide valuable insight in defining the
search area
Doherty, P., Guo, Q., Liu, Y., Wieczorek, J., and Doke, J., “Georeferencing Incidents
from Locality Descriptions and its Applications: a Case Study from Yosemite
National Park Seach and Rescue”, Transactions in GIS, 15(6): 775-793, 2011..
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

13. Statistical Search Area
 Assume you are the
administrator for a
regional park.
 The park consists of a
series of trails with 11
different trailheads.
 This park is used
primarily by day hikers
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

14. Statistical Search Area
 Other the course of the
previous year you had 100
SAR incidents occur within
your park.
Limited the dataset to only
subjects reported as missing.
Although your subjects ranged
in age from 15 – 85 they all
reported being in the park to
hike.
As a result of good record
keeping you had coordinates
for both the find and the IPP.
In 100% of the cases the IPP
was a subject’s vehicle parked
at one of the trailheads.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

15. Statistical Search Area
 Although you did not have
data reporting the actual
distance the subject had
traveled from the IPP to the
point that they were
found, you can measure the
straight-line (crow-flies)
distance between the IPP
and the find location.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

16. Statistical Search Area
 With the IPP-Find Distance from IPP to Find (km)
distances plotted 16
we can easily see
14
the min and max
values (Range) 12
Distance (km)
Min = 0.4 km 10
Max = 14.5 km 8
6
 Also may be 4
interested in the
2
mean or average
distance recorded 0 13
17
21
25
29
33
37
41
45
49
53
57
61
65
69
73
77
81
85
89
93
97
1
5
9
Mean = 5.8 Incidents in Chronological Order
 While interesting, the distances could contain “outliers” that could
impact the value of the statistics.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

17. Statistical Search Area
 If however, the Distance from IPP to Find (km)
distances are 16
sorted by length
14
we can obtain the
“median” value 12
Middle value of an
Distance (km)
10
ordered set of
8
numbers
Median = 5.2 km 6
4
2
0
0 20 40 60 80 100 120
Incidents Sorted by Distance (low - high)
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

18. Statistical Search Area
 If however, the Distance from IPP to Find (km)
distances are 16
sorted by length
14
we can obtain the 12.0 km
“median” value 12
75%
Distance (km)
Middle value of an 10
ordered set of 95%
numbers
8 50%
8.0 km
Median = 5.2 km 6 25%
4
5.2 km
 Quartiles 2
3.23 km
Divide the 0
distances into four 0 20 40 60 80 100 120
equal groups Incidents Sorted by Distance (low - high)
25%, 50%, 75%
and 100%
 Due to outliers, the 100% distance may not be of interest so limit the
data to 95%.
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19. Statistical Search Area…Application
 Return to the original
IPP and find locations.
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20. Statistical Search Area…Application
 Let’s consider only the
IPP for a moment.
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21. Statistical Search Area…Application
 Let’s collapse all of the
IPP’s to a single virtual
IPP as shown on the
map.
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22. Statistical Search Area…Application
 If we now re-plot
virtual find locations at
the same distances of
our actual IPP-Find
distances we would
end up with a
distribution that looks
similar to this
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

23. Statistical Search Area…Application
 If we divide up the
100 find locations into
groups of 25
Draw a ring around the
closest 25
Draw a second ring
around the next closest
25…and so on
 If we assume that
behaviors of “hikers”
within the park is
similar then we would
expect other lost
hikers within the park
to be found at similar
distances. However, we are not always just looking for lost
More data is better hikers and sometimes we need to look for subjects
outside of our own park.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

24. Statistical Search Area…Find Locations
 What if you also had collected data on the find
location and categorized it by a predominate feature.
Feature Percent
Road 3% Find features for “Hikers”
Fields 4%
Woods 88%
Using readily available
geospatial data to “reclassify”
spatial data to coincide with
Find Locations
Koester, R.J., “Lost Person Behavior: A search and
rescue guide on where to look - for land, air and
water”, dbS Productions LLC, 2008.
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

25. Statistical Search Area…Find Locations
 Utilize: roads, trails and drainage layers along with
land cover data (from National Land Cover Database)
Roads, Trails
and Drainages
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

26. Statistical Search Area…Find Locations
 Identify features where finds are made. These
features may or may not represent attractants for the
subject category
Find Locations
Roads – 3%
Fields – 4%
Woods – 88%
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

27. Statistical Search Area…Track Offset
Consider the shortest distance
between a linear feature
(roads, trails, drainages, power
line ROWs, etc) and where the
subject was found.
Track Offset
(meters)
25% 70
50% 126
75% 254
100% 964
Feature (0-20 m)
25% (21-70 m)
50% (71-126 m)
75% (127-254 m)
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

28. Statistical Search Area…Elevation
Consider the difference
in elevation between
the IPP and where the
subjects were found.
Elevation (meters)
3% +/-20
42% +21 : 1701
55% -1606 : -21
+/- 20 m
+31 : 1701 m
-1606 : -21 m
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

29. Statistical Search Area…Mobility
 Similar to the Theoretical Search Area, data is
collected from subjects regarding the length of time
they were mobile.
Because we can predict travel
time from spatial data (land
cover, terrain, travel aides, etc)
we can estimate travel time
within the search area.
Mobility (hrs)
25% <3
Mobility (hours)
50% <5
1
100% 9 2
Note: Steep slopes inhibit 3
access within this area. In 4
this hypothetical situation the 5
IPP (orange symbol) was
6
adjusted due to its original
location being position on a 7
steep slope. 8
>8
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30. Statistical Search Area
International Search and Rescue Database
 ISRID project began in 2002 focused on the
collection of information from missing/lost person
incidents for the purpose of understanding lost
person behavior
Currently contains over 50,000 missing/lost person incidents
41 subject categories
Statistical Search Area defined as the straight line distance
(“Crow Flies”) from the Initial Planning Point (IPP – typically
the last known location of the subject) to the find location.
Additional analysis provided on the nature of the find
location (structure, water, woods, etc).
Koester, R., “Lost Person Behavior”, dbS Productions, Charlottesville, VA, 2008
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

31. Statistical Search Area
 Utilize historical data to predict location of current
missing subject.
We are all a creature of habit even when we are lost.
 Results from ISRID have been published in “Lost
Person Behavior”
Data from various eco-regions and includes 41 different
subject categories
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group

32. Modeling Lost Person Behavior
Statistical Search Mobility Model Elevation Find Location
Area Difference Model Model
Track Offset Hazardous
Model Terrain Model Operational
Appalachian Search and Rescue Conference Map
Mountaineer Area Rescue Group

33. Questions?
Contact information:
Don Ferguson
Mountaineer Area Rescue Group
dferguso@mix.wvu.edu
(304) 290-9118
Appalachian Search and Rescue Conference Mountaineer Area Rescue Group