Photogrammetry - What is it? Why use it? Does it Work?
What is it?
Photogrammetry is the science of extracting measurements (metry) from photographs (Photogram). Photogrammetry has been around in some form since the second world war when photography started to take an important role in remote sensing.
Computational photogrammetry has been around since the early days of computers. The increasing power of computers, the introduction of the modern graphical user interface, and the introduction of the mouse in the 1980's and 1990's allowed computational photogrammetry to be run on everyday desktop computers.
Why use it?
Photogrammetry is a valuable measurement tool in all areas of forensic investigations and has been a very powerful tool to us as forensic crash reconstruction experts. From measuring the height of subjects in surveillance video, measuring blood spatter and measuring crash scene evidence and vehicles, photogrammetry is a tool we frequently use.
Does it work?
Yes, very well! There frequently are occasions when important scene evidence is missed or not measured at the scene of crash but is captured within scene photographs. Photogrammetric analysis using PhotoModeler software has repeatedly permitted us to plot and measure the evidence within the photographs for further forensic analysis in determining what happened in the case.
We are experienced, trained and certified in the use of the industry leading photogrammetry software called, PhotoModeler (exterior link: here ) which we frequently used in our forensic tool-set to render our expert opinions.
Real World Examples of Photogrammetry -
Two Vehicle Collision - No Police Measurements Taken at the Scene
A collision reconstruction analysis was performed in a case where no crash scene measurements were taken by law enforcement but scene photographs were taken. Photogrammetry was used to measure the crash scene and determine how the collision occurred. The diagram files below were generated from CAD data exported from PhotoModeler: (Click on each image to open the diagrams in a seperate window)
Fatal Motorcycle Crash - Police Missed the Pre-impact Motorcycle Skid Mark
A fatal motorcycle versus pickup truck occurred. Law enforcement personnel missed a pre-impact motorcycle skid mark during their scene processing but the skid mark was visible in multiple scene photographs. We were able to plot and measure the pre-impact skid mark generated by the motorcyclist prior to impact.
There are no diagrams available for this case but the images to the left show a red line visible within the roadway, which is the PhotoModeler overlay line-work from the photogrammetry project.
Here are some real world examples where photogrammetry was used to measure scenes