Five Reasons to Use Photogrammetry

Photogrammetry has been gaining popularity in the forensics community recently, especially in the field of accident/collision reconstruction, and here are five reasons why. 

1. Never miss another measurement. Have you ever come back from measuring a vehicle with a total station or crush jig only to find you missed a measurement? With photogrammetry, you'll never be in that situation again. Measurements can be added post-haste when you get back to the office even if the point of interest wasn't targeted. 

2. Measure Crush from Appraisal Photographs. This is simply something that can't be done with any other method. With insurance budget cuts, we (reconstructionists) are often hired years after the collision occurred in preparation for trial, and the vehicles are no longer available for inspection. Need to perform a crush analysis? As long as two good photos of the damage exist, it's no problem. Fire up Photomodeler or iWitness, download an exemplar from Lightpoint Data for control points, and solve away. There is a video tutorial documenting the process in Photomodeler here

3. Speed. Measuring vehicle crush using photogrammetry is almost always faster, and scene mapping can be as well at times. 

4. Visual error. This is someting Randles, et al, discuss briefly in SAE 2010-01-0065. Any errors become blatant by analyzing the residual error reports in Photomodeler or iWitness. The erroneous points can then be viewed in the project photographs to determine if the point was improperly marked, or if there is a more serious systemic problem. If a total station measurement was taken improperly, there may not be a way to know, or correct it. 

5. Easy to prove accuracy and share. When asked to document the validity of your model, you can simply supply the curious party with a project report from Photomodeler of iWitness. In addition, you can supply the actual project, so other reconstructionists can see for themselves if there are any issues with your model. 

If your firm isn't using photogrammetry yet, it's time. There are too many benefits to ignore.

Thanks for reading,

Louis Peck, MSME
ACTAR #1663
Lightpoint Data