ITE Journal July 2018 - 40

2. Install or apply scaling control markers. Pavement nails with
fluorescent orange markers were driven into the pavement
(Figure 2a and Figure 2b). Measurements between these control
markers are used to scale the imagery collected by the UAS.
3. Mark critical items that may have reduced visibility in aerial
imagery. The start and end of the skid mark on the pavement
were marked using white marking paint (Figure 1b). The control
markers were labeled according to Purdue Police convention
using the paint (Figure 2c).
4. Measure the distances between the scaling control markers.
A tape measure was used to find the distance between the 6
control markers (Figure 2d). Only 2-3 manual measurements are
needed for scaling control, but additional measurements were
obtained to provide an independent check of the final ortho-rectified image.
5. Identify a safe flying altitude. The UAS pilot must check that
there are no obstacles within the intended flight path. This can
be done by raising the UAS to different altitudes and checking
by eye for any potential hazards. Common obstacles to watch for

include trees, telephone wires and poles, buildings, and vehicles.
For this mission, the flight altitude was 20 meters above ground
level.
6. Plan and fly a mission. Most consumer-grade UAS can follow a
pre-programmed flight plan and there are various applications
that can be used to plan a mission.
7. Clear the incident scene as per standard traffic incident
management policies.

UAS imagery
UAS can be used to collect images that cover a larger area than
ground-based photography. Occlusion of vehicles and objects of
interest become less of an issue at greater heights. Oblique images
(Figure 3a) from above the crash scene can provide good situational
context that a single ground-based photo cannot. However,
these images are difficult to scale, are challenging in identifying
common features for ortho-rectification, and have more occlusions.
Nadir-looking images (Figure 3b) can be easily scaled and
ortho-rectified. The altitude of the UAS determines the resolution

(a) Installation of control markers

(a) Oblique image

(b)Close-up of control marker 1

(c) Spray painting label for control
marker 1

(d) Manual measurement of distance between control markers 1 and 2

(b) Nadir-looking image

Figure 2. Establishment of scaling control markers for staged crash scene.

Figure 3. Example images from UAS camera.

40

J ul y 2018

i te jo urn al



Table of Contents for the Digital Edition of ITE Journal July 2018

ITE Journal July 2018 - Cover1
ITE Journal July 2018 - Cover2
ITE Journal July 2018 - 3
ITE Journal July 2018 - 4
ITE Journal July 2018 - 5
ITE Journal July 2018 - 6
ITE Journal July 2018 - 7
ITE Journal July 2018 - 8
ITE Journal July 2018 - 9
ITE Journal July 2018 - 10
ITE Journal July 2018 - 11
ITE Journal July 2018 - 12
ITE Journal July 2018 - 13
ITE Journal July 2018 - 14
ITE Journal July 2018 - 15
ITE Journal July 2018 - 16
ITE Journal July 2018 - 17
ITE Journal July 2018 - 18
ITE Journal July 2018 - 19
ITE Journal July 2018 - 20
ITE Journal July 2018 - 21
ITE Journal July 2018 - 22
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ITE Journal July 2018 - 24
ITE Journal July 2018 - 25
ITE Journal July 2018 - 26
ITE Journal July 2018 - 27
ITE Journal July 2018 - 28
ITE Journal July 2018 - 29
ITE Journal July 2018 - 30
ITE Journal July 2018 - 31
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ITE Journal July 2018 - 33
ITE Journal July 2018 - 34
ITE Journal July 2018 - 35
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ITE Journal July 2018 - 37
ITE Journal July 2018 - 38
ITE Journal July 2018 - 39
ITE Journal July 2018 - 40
ITE Journal July 2018 - 41
ITE Journal July 2018 - 42
ITE Journal July 2018 - 43
ITE Journal July 2018 - 44
ITE Journal July 2018 - 45
ITE Journal July 2018 - 46
ITE Journal July 2018 - 47
ITE Journal July 2018 - 48
ITE Journal July 2018 - 49
ITE Journal July 2018 - 50
ITE Journal July 2018 - Cover3
ITE Journal July 2018 - Cover4
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