Epsg:8083 gcp

Looking through similar questions, I’ve seen responses that EPSG should be supported directly. However, when loading the GCPs, I get the “Unknown projection EPSG:8083” error. What should I use instead (as the first line in the GCP file)?

EPSG:8083 → NAD83(CSRS)v6 / MTM Nova Scotia zone 5

EPSG:8083
gcp1 25518761.52880 4905394.50872 2.68864
gcp2 25518771.86487 4905361.67780 2.64688
gcp3 25518783.57559 4905366.86062 3.03977
<...>

Thanks!

g

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I had the same problem

Try a proj4 string.

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Right, that’s the answer I see the most but nothing explaining how to build a proper proj string for something like NAD83(CSRS)v6 / MTM Nova Scotia zone 5 (or any MTM).

Thanks!

This page normally has proj4 for all ESPG but it doesn’t appear to be one for the one you got.

It does but it appears the page is not rendering properly.

I will see if I can make sense of the raw XML.

Thanks!

Not sure if this is the same one:
https://spatialreference.org/ref/sr-org/8083/

I had seen that before posting the question. That puts me south of Australia.

Here is a related discussion, which is way over my head:

https://groups.google.com/g/lastools/c/uFlm2nb3W1w/m/keAbtgDICQAJ?pli=1

Ah, well Isenburg was a genius, rest his soul, so no surprise the thread is hard to follow.

Without diving into that, which may go deeper than we need, do you have an existing .prj for your coordinate system? If so, we can probably munge together our own proj4 string.

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Not really. I use WGS 84 / UTM zone 20N for everything. QGIS can load those EPSG:8083 GCPs fine. Let me see if there is a way to transform it (this is a hobby so it’s not like I know what I’m taking about…)

Thanks!

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This is what QGIS is doing:

Inverse of MTM Nova Scotia zone 5 v2 + Inverse of ATS77 to NAD83(CSRS)v6 (4) + ATS77 to WGS 84 (1) + UTM zone 20N

  • Scope: Spatial referencing.
  • Scope: Approximation at the +/- 1-2m level.

Area of use: Canada - Nova Scotia - west of 63°W, Canada - Nova Scotia, Canada - New Brunswick, World - N hemisphere - 66°W to 60°W

Identifiers: INVERSE(EPSG):8081, INVERSE(DERIVED_FROM(EPSG)):9106, DERIVED_FROM(EPSG):1688, EPSG:16020

+proj=pipeline +step +inv +proj=tmerc +lat_0=0 +lon_0=-64.5 +k=0.9999 +x_0=25500000 +y_0=0 +ellps=GRS80 +step +inv +proj=hgridshift +grids=NS778302.GSB +step +proj=hgridshift +grids=NB7783v2.GSB +step +proj=utm +zone=20 +ellps=WGS84

For what’s worth, in QGIS, if you export the (previously loaded GCP) layer as a CSV file, you can define the target CRS and it will spit out the point list in the corresponding CRS. That should do it. Now I need to go figure out how to actually load the GCPs into WebODM :stuck_out_tongue_winking_eye:

Thanks!

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Perfect! Awesome.

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