GeoSLAM traj_ref.txt – Export Reference Points

Lately, after buying our GeoSLAM system we did our first campaign and we found out we needed to Export Reference Points from the processed data.
This operation used to just work with GeoSLAM Hub, unfortunately we cannot use GeoSLAM Hub to process data as our scanner is equipped with the GeoSLAM Vision camera, that is only supported by the newest GeoSLAM Connect.

While writing, GeoSLAM Connect does not offer Export Reference Points function, luckily it is providing users with a file named traj_ref.txt file, containing coordinates and some other useful data.
The bad news is that such Data is *NOT related* to the Base/CrossHair.

What does that mean?

It means that you cannot just use coordinates contained in traj_ref.txt as Reference Points of your resulting dataset.

First 3 columns coming from traj_ref.txt are providing us with emitter-related coordinates, they are and not CrossHair/Base-related

Coordinates there are far from a real Reference Point measured with the CrossHair on the base: about 20cm off on Z axis and about 11cm on 2D axis (X+Y)

When measuring a reference point on a vertical wall the offsets are reversed: (11cm off on Z axis, 20cm off on 2D)

The following image shows Yellow Crosses as real positions, Magenta Circles are placed according to traj_ref.txt Coordinates.

What to do then?

We know traj_ref.txt contains X,Y,Z (emitter-related coordinates) and angular informations.

Such data, together with some device-internal data can be used to reproject emitter-based coordinates to CrossHair-based coordinates.
As we didn’t get any offical data yet from support, it became a matter of some Hamiltonian maths and some experimental physics to recover some data within an acceptable accuracy.

Ok, but I am no math genius! How to do that?

We did all of that for us, and decided to put this work online for people to use it.

This comes from a ten of samples we did by ourselves, it can be not so much to accurate: if your results seem to be inaccurate please stop by and send us your data, so that we can improve our algorithm!

We are still keeping in contact with producer: we hope to get official reprojecting data soon or just to get the export function applied on Connect, stay tuned!

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