Crash Technology Bulletins



Crash Technology Bulletin #1

A common question: Are satellite images accurate enough for crash reconstruction purposes?

Watch the video to see the answer to this question.


These days, more and more crash reconstructionists are using satellite or aerial images as part of the standard 2D scene diagram. It is probably the most interesting and informative technology that has been applied to crash reconstruction in recent years. As a result, more and more software developers have created an interface to Google maps or Bing maps so the accident scene location image can be directly imported by accessing that function from the program interface.

Important facts to know about using satellite images:

1.

Some rumours have been spread in the industry that satellite images from Google or Bing are taken at an angle which makes them inaccurate and useless for crash reconstruction. That is not true. Although it is true the image sensor relative to the area of interest may not be orthogonal, the image is orthorectified and can be relied upon to be accurate. To understand that the images are accurate, reconstructionists using the imagery must understand the orthorectification process utilized before we access and apply the satellite images to crash reconstruction, as you may be required to explain the accuracy in court.

2.

Digital satellite images and aerial photographs play an important role in general mapping, as well as GIS data acquisition and visualization. In addition, the secondary and perhaps more vital role, is to provide a basis for analyzing spatial information such as images used in crash scenes. Before this information can be gathered in a manner that is useful for a mapping or GIS system, the satellite image data or aerial photographs must be prepared in a way that removes distortion from the image. This process is called orthorectification. Without this process, you wouldn't be able to rely on accurate measurements of distances, angles, positions, and areas.

3.

Many tests have been done to match the x,y positions of survey points to the corresponding points on Google images and they match perfectly time after time. Therefore, the images are perfectly accurate and suitable for use in accident reconstruction diagrams.

4.

At FARO Technologies Inc. we have conducted tests matching total station points to corresponding satellite photo points and have found precise accuracy in all cases.

Conclusion

If you are using aerial images that have not been orthorectified, you are using inaccurate information and will need to find a way to orthorectify those photographs. Otherwise, you may face stiff criticism at trial. However, you can use satellite images with confidence as long as they are properly scaled because those images have been orthorectified.




If you have any questions, please contact us at 1.877.814.2360 or send an email to info@aras360.com.