Close range scan of some heavy vehicles.

With occlusion “false”, it is difficult to see foreground pounts because of may additional layers of data in the background. Rendering speed is also lower because of the higher number of points in the dataset.

With occlusion “true” (below) the foreground points are now much easier to see due to background data being hidden. Note that windows, doorways amd other surface “holes” are correctly handled.

Laser scanning collision investigation

TERRADAT recently untertook a trial of laser scanning for a two car collision with the help of South Wales Police.

The Topcon GLS-1000 laser scanner was used on two stations either side of the scene. The stations were referenced using the BS/OBS method (stations and one BS target were georeferenced with a total station).

A test was also carried out to investigate the use of a grey masking spray to increase the reflectance of the car body panels. Click here to view the data and photographs from the survey.

The main conclusions are as follows:

- the silver and green cars gave usable returns although low intensity
- spraying the grey masking paint significantly improved things (see
comparison images) and enabled the tyres to be scanned
- the rear bumper of the Fiat was not resolved. I think this was due
to the incident angle in relation to the scanner.
- the skid marks on the ground caused by the Fiat were mapped
- the test was very quick: we achieved two scans, and coordinated them
using a total station to enable quick registration in under 45 minutes
- the scanner also picked up surroundings within a range of around 175m which could be of interest for getting a scene overview

The data could be measured and analysed in the free Topcon Imagemaster
viewer. I will send you the project to look at in the viewer.