Vehicle recording geometry of railway site structures
Geometry is measured by photographing the trace of a rotating
laser beam on the facing of the structure under check. Beam rotation is obtained by a
mirror turning at 50 revs per second.
The images are retrieved by a high-resolution CCD camera:
1000 x 1000
Thanks to computer processing of the grey levels, resolution
is increased to 4000 x 4000 pixels (field resolution = 3 mm).
Laser telemetry Geometry measurements are also made with a
modulating laser enabling resolutions of around 1 cm to be obtained for distances of
around 30 metres at a rate of 40,000 measurements per second. Associated with a rotating
mirror system, this telemetry system measures positions and shapes :
