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Overview
There are two types of scene diagramming possible with PhotoModeler: a) using a calibrated camera to photograph a current scene, and b) working with photographs from unknown cameras of a scene from the past. On this page we discuss the first, which is using a calibrated camera to document a scene before it has been cleared of vehicles. This process is typically carried out by a police department's incident team.
The two main benefits of using photogrammetry to document an accident scene are speed and cost.
A complex scene that required accurate measurement was often captured with a surveyor's total station but this was very time consuming. There is a lot of pressure on law enforcement agencies to reopen roads as soon as possible, but they have a duty to properly document the scene - as that evidence may be needed by a court at a later date. By using their own camera and some evidence markers they can document the scene quickly and accurately, and then reopen the road far faster than if they used other measurement and diagramming techniques.
The reduced cost comes from the low cost and portability of a camera vs a total station. Within a fixed budget, an agency can get more cameras and sets of evidence markers into service vehicles than total stations.
Examples
Here are two examples of accident scenes diagrammed using PhotoModeler.
| From Photos to 3D Court Presentation |
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| Courtesy of DCM Technical Services |
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This incident between a GMC pickup and a Saturn at a rural intersection was documented with photographs from a police-owned camera and evidence markers. Not only was a scene diagram created, but an ortho-photo was used to check tire mark shape, and some crush measurement was done at the scene (again using PhotoModeler).
The top image is a photograph of the scene with the pickup truck in the foreground with skid marks, and the Saturn sedan in the far background on the field.
The second image is a 2D diagram created in CrashZone from the data exported from PhotoModeler. PhotoModeler is a full 3D package but can easily export data projected on a plane for 2D mapping.
The third image is an ortho-photo of part of the road surface showing the skid marks. One cannot get the true shape of the skid mark in a photograph taken at ground level due to perspective distortion. The rectification and ortho-photo function of PhotoModeler creates an output image that removes the perspective distortion - as if the photograph was taken from in the air over the road. The true shape of the skids can be studied in such an image.
The last image shows a 3D view of the 2D diagram in CrashZone - suitable for court and jury presentation, as some may find it easier to understand.
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| Combining Aerial and Ground Photos |
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This incident, which involved fatalities and a major vehicle fire, was photographed from the ground and from an aircraft and then modeled by one of the state police agencies.
The top image shows one of the aerial photos that was combined into the project. The middle image shows PhotoModeler with some of the ground photos. The bottom image shows the resulting scene diagram. |
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