Creating coordinate system from a model

[gisilpals]

Hey there,

I have a set of images I made a model from by creating markers on the fly. There was no associated coordinate system or geolocations. I now want to use that initial model to generate coordinates for GCPs to use for another model of the same place. It is very obvious that my model has an internal coordinate system, but there is no way to display XYZ. Can anyone help with this?

I'm basically just comparing two models taken of the same phenomenon at different times, in arbitrary space, where the first model is used to control for the second model based on elements in the two models that are recognizably identical.

[william]

The Python API has a method chunk.exportMarkers(), and also a method chunk.importMarkers(). So those should probably work. But it seems like what you really need is a way to automatically detect the markers in the 2nd model, so that you can automatically align the 2nd model to the 1st one.

Assuming you're not using PhotoScan's auto-detectable markers, it seems like the best thing to do is manually locate the markers in both models, then chunk.exportMarkers() from both, and do whatever analysis you would like to compare the two sets of coordinates.

[SB]

As said above, or

If you ware wanting to combine with laser scan data you should use scale bars to get the coordinates as close to laser coordinates as possible.  You can use many 3D model viewing applications to pick a point and get xyz data.  I like CloudCompare.

You may find it easier to get several xyz points from the data that you will import into Photoscan first and then assign your markers the same xyz coordinates (in essence make some GCPs with data from the other coordinate system to get Photoscan
in the same plane)  GCPs do not have to be real world coordinates...

You will need Photoscan Pro to do any of what I'm suggesting though.

SB

[Packy_GIS]

Actually - if you want to establish your local coordinate system, than you require at least 2 points. You choose one as the beginning of the coordinate system [0, 0, elevation], than measure distance to the second point and this point will have coordinates [0, distance, elevation]. Based on this you may start calculating the other point's coordinates using trigonometry or measure the points using a total station. The laser scanning should you the exactly same coordinate system and the point clouds should match exactly!
I do exactly the same when I am documenting archaeological research in desert, where is no coordinate system nor RTK GPS available.
Packy

[Alexey Pasumansky]

Hello gisilpals,

If you are using the latest release version of PhotoScan Pro, then you can use Create Marker tool on the 3D model and the newly created marker instance in the Reference pane would contain the 3D coordinates of the point in the Source values tab, according to the current internal coordinate system. So it would also work for unreferenced models.