1. What is a typical use of Lightpoint's exemplar database?
A substantial portion of our customers use our photogrammetry exemplar package to solve unknown camera projects (crush from scene or appraisal photographs) in Photomodeler or iWitness. The other major portion of our customers use the DXF / CSV exemplar files to merge with their damaged model (typically measured by hand, total station or laser scanner) for straightforward crush measurement. The models can also be merged easily with a photogrammetry project of a damaged vehicle, of course.
2. Do I have to be a photogrammetry user to make use of your exemplar database?
No. If you measured the damaged vehicle by hand, or using a total station, the exemplar DXF / CSV files can be merged with your measurements in any CAD program, and is likely the product for you.
3. Exactly what is included with each purchase?
Each exemplar package includes: at least eight high-quality photographs, completed Photomodeler and iWitness photogrammetry projects, related camera calibration information, photogrammetry result reports, a DXF drawing, and a CSV file.
4. Does Lightpoint offer any guarantee?
Yes. If you are not satisfied with any portion of the exemplar package just let us know and you'll receive a 110% refund for your trouble.
5. What measurements are included in Lightpoint's models?
Measurements are obtained on the side at the sill height and mid-door height, which is the height at which crush measurements are taken during the NHTSA crash tests that provide the information to derive relevant stiffness coefficients. With respect to the front / rear, measurements are documented at the frame height, as well as on relevant areas of the hood / trunk. Additionally, the center of each wheel is measured. Other targets are placed around the vehicle in case more unusual measurements are needed and to assist in solving the model photogrammetrically.
6. Why not just use a rectangular "exemplar" based on published vehicle specifications?
Simply put, accuracy. Modern vehicles are not rectangular, and as a result, an analysis performed under such an assumption may lead to drastic overestimation of the amount of deformation sustained by the involved vehicle, and ultimately, inflated speed calculations. The image below shows a rectangular "exemplar" placed over our 2011 Chevrolet Cruze exemplar. The gray highlights the difference in the bodyline, while the blue highlights the difference at the sill.
7. But, don't modern vehicles have Event Data Recorders?
Yes, many modern vehicles do indeed have Event Data Recorders. However, in most cases it is necessary to support that data with traditional collision reconstruction practices such as conservation of momentum and crush analysis. Attempting to testify without such support is risky.
8. Why aren't targets placed in a manner that would capture the entire curvature of the wheelwell opening, and why are some targets on bumpers placed at different heights?
As the models are for the purpose of crush analysis, priority is given to the X-Y plane (aerial view). For that reason, a target near the central portion of the bumper cover may be placed above the license plate bracket, while others on the bumper are not, to capture the proper profile of the bumper itself. Similarly, the X-Z plane curvature of the wheelwell opening is not important for crush analysis.
9. I am interested in a specific measurement that is not targeted in the model, could the measurement be obtained?
Usually, yes. If you are a photogrammetry user, most measurements of interest can be obtained post-haste since you'll have access to a complete photogrammetry project. If the points you're interested in can be referenced in at least two photographs, the program will solve for their location. For the DXF / CSV package, if you need a specific measurement that's not included, please contact us and we'll likely be able to add the measurement for a minimal fee (or in some cases, no cost).
10. Will I be able to download the exemplar information immediately?
Yes. The information is available for download immediately upon payment via the link shown after payment or the link sent to the provided email.
11. How accurate are the measurements Lightpoint provides?
We recently performed an in-depth analysis that shows our models are accurate to 1.2 mm when compared with a FARO Arm. More details on the topic can be found here.
12. Can your photogrammetry models be used to solve inverse cameras? In other words, if I'm provided photographs of a crushed vehicle, but don't know anything about the camera used to take those photographs, could I create a model of the crush using Lightpoint's exemplar models?
Yes. Our photogrammetry models can be used to supply the necessary control points to solve an unknown camera. PhotoModeler has an in-depth tutorial detailing the process, which can be found here.
13. I'm not a photogrammetry user, is there any documentation provided detailing the accuracy and validity of the model that does not require access to either program?
Yes. Reports showing the results of the photogrammetry project can be supplied if requested. In addition, you can cite our thorough research, which will be published in SAE in April of 2016).
14. Does Lightpoint ensure the exemplar vehicles used for their models have not been in collisions?
We ensure there is no unrepaired damage that would affect the exemplar model as it pertains to crush analysis. For example, if there is evidence that a door was repainted at some point, but the repair was performed properly and there are no unusual bodylines or protruding edges, the vehicle is deemed acceptable. Similarly, if there is a dent on the roof, that damage will not affect the model and therefore the vehicle is acceptable. Vehicles with blatant damage, or damages not properly repaired, are not included in the database.
15. What are the measurement units of the supplied DXF files?
Inches. However, if you wish to receive the DXFin another format, please just let us know.
16. I cannot open the supplied DXF file with my CAD program.
No problem. Just email email@example.com and specify the CAD program you're using and a compatible DXF will be supplied right away.
17. I don't see the vehicle I need in the database, do you take requests?
Yes. We can obtain exemplar measurements of most vehicles within 5 business days.
18. How do your exemplars save me time or money?
Instead of taking the time to locate, travel to/from, and measure an exemplar vehicle (a process that typically requires 3-4 hours) our packages are available for immediate download. If you are billing $175/hr, it would cost your client $525+ for an exemplar model compared to our $250. Therefore, you can save yourself time and your client money, which will keep your client happy and loyal.
19. Are there any published studies validating the use of photogrammetry for collision reconstruction?
Many. The most recent of which is a 2010 paper published by the Society of Automotive Engineers and written by Bryan Randles, Brian Jones, Judson Welcher, et al, titled "The Accuracy of Photogrammetry vs. Hands-on Measurement Techiques used in Accident Reconstruction." Additionally, Dan Mills of DCM Technical Services, Inc., wrote a similarly useful paper in 2005 that can be found here. Many other papers have addressed the issue and found the technique to be valid in our field. In addition, as mentioned throughout our site, we have recently completed a study that has been submitted to SAE for publication, the abstract can be found here.
20. What payment methods are accepted by Lightpoint?
Visa, Mastercard, American Express, and Discover are accepted for immediate downloads. Checks and POs are accepted as well, but the product download link will not be sent until payment has cleared.
21. Does Lightpoint offer a subscription based service?
Annual pricing will be offered very shortly.
22. Has photogrammetry been accepted at trial?
Yes, many times. Click here to download a partial list of known cases.