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Scene Mapping

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Scene Mapping – PowerPoint PPT presentation

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Title: Scene Mapping


1
Scene Mapping
Gwinnett County Police Department Accident Invest
igation Unit
2
Purpose for Mapping
  • Investigation / Reconstruction
  • Show vehicle positions, impact points, vehicle
    paths, and traffic control
  • The maps are used to obtain measurements to
    calculate vehicle speeds, positions in relation
    to each other based on time, sight distance
    problems
  • Re-creation of the collision

3
Purpose for Mapping
  • Court / Prosecution
  • Show vehicle positions, impact points, vehicle
    paths, and traffic control to the judge and jury
  • By changing the scale, the size of the map can be
    enlarged to become an important visual exhibit
  • Its furnished to the defense and they can see
    the case is well prepared for court.

4
Several Ways to Create
  • Measuring Tape (Two Dimensional)
  • Coordinate Offset Method
  • Triangulation
  • Total Station (works on a type of triangulation)
    (Three Dimensional)
  • Real Time Kinetics (Global Positioning System)
    (Three Dimensional)
  • Photogametry (Three Dimensional)

5
Total Station
  • Components
  • Head
  • Data Collector
  • Tri-pod
  • Survey Rod with prism (adjustable height from
    .25ft to 25ft

6
Total Station
  • Components
  • Head

7
Total Station
  • Components
  • Data Collector

8
Total Station
  • Components
  • Tri-pod

9
Total Station
  • Components
  • Survey Rod with prism

10
Application
  • Widely in use
  • Good for every type of scene
  • Accesses points that are hidden behind objects
  • Can be used at night and in moderately foul
    weather conditions
  • Setup is about 5 minutes
  • Can be used while emergency crews are on scene

11
Manpower Requirements
  • One operator and one person for each prism. At
    least one prism is necessary.
  • There are systems that can be operated by one
    person.
  • Once the data is collected, it must be uploaded
    onto a computer to process

12
Different Types of Usage
  • May be used during the on-scene investigation
  • May be used after the scene is cleared by having
    the evidence marked
  • May be used again to add points not previously
    collected.
  • The data may be merged onto an aerial view of the
    scene. Combining Total Station and Photogametry

13
Typical Application
  • If used during the on-scene investigation, the
    investigator would place the prism at each point
    of reference and a shot would be taken. This
    would be repeated for each point of reference,
    the vehicles, roadway evidence, and traffic
    control. The dimensions of the roadway may also
    have be referenced.

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15
Typical Application
  • The base would be placed and marked so it could
    be used again if necessary.
  • Using the system while the on-scene investigation
    is being made extends the time on-scene. Whether
    this is best for the situation depends on the
    roadway and traffic conditions.

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18
Typical Application
  • If the evidence is marked, the scene can be
    shot on a better date and time for the traffic
    conditions. All the obstructions would be gone
    and the traffic can be controlled with better
    planning and appropriate manpower.

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21
Aerial Photogametry
  • If the investigator has access to aerial
    photogametry he need only shoot a few reference
    points and the collision evidence. The reference
    points are used to match the data with the aerial
    and produce the roadway by tracing the aerial.

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23
Conclusion
  • The best method of producing a scale diagram of a
    collision scene is a combination of the two
    systems. The Total Station is the best method for
    the on-scene evidence and works well in all
    situations and almost all types of weather. Its
    generally not limited by terrain characteristics.
    The investigator needs to only be trained on one
    system.

24
Conclusion
  • Rather than survey the roadway dimensions, the
    computer operator uses the aerial photogametry
    and combines the data with the aerial view. The
    result is a merging of the two systems.
  • By marking the evidence with traffic paint or
    nails and returning at a better date and time to
    collect the reference information, the traffic
    disruption is minimized.
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