What processes do you do to judge the quality of the scan/scanner?

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akeane
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What processes do you do to judge the quality of the scan/scanner?

Post by akeane »

Using Cyclone core for this, but I'm more proficient with realworks.

Suppose you've just gotten a brand new scanner and know nothing about it, what processes do you undertake to judge the quality of a scan and/or registration?

Previously what I've done in the past is scan a flat surface such as a whiteboard, granite surface, or a finished precast wall, and then take a horizontal cross section and look and the range of the bands of points. Ie i would expect in a 50mm thick cross section there would be <3mm variation of points (depending on distance), with the mean being the correct value.

I would see what the direct fit of an observation of 3 BW targets against the same 3 targets measured with a total station.

I would also inspect the .fls images from the instrument perspective to see if there is any obvious tearing.

To compare the accuracy of the overall registration, i would colour each scan by the station, then look at the overlap of the scan data to see if there is a strong correlation.

I'm sure there are other tricks; feel free to write yours below.
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Re: What processes do you do to judge the quality of the scan/scanner?

Post by smacl »

In addition to the above I'd also consider the following (coming from a roads and topo background);
  • Check a level surface (as opposed to a flat one that may not be level) to check the compensator
  • Check sharpness of intensity returns, coloring by intensity and looking at something like road markings
  • Compare relative position of a road marking when coloring by intensity versus coloring by RGB to check camera alignment
  • Check noise levels on dark matt surfaces and dark shiny surfaces, some scanners struggle here
  • Check how easy it is to adopt external control
  • For mobile mapping, check the density and pattern of scan points, preferring parallel even spacing over scattergun patterns.
  • Check field to finish time, from starting to scan to having a clean, registered point cloud
Shane MacLaughlin
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www.atlascomputers.ie

SCC Point Cloud module
akeane
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Re: What processes do you do to judge the quality of the scan/scanner?

Post by akeane »

Thanks Shane, this was very informative
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