Stuck with coordinates for control point file

Hi nice to meet you all.
I’m new at this, trying hard and with a lot of enthousiasm.

I got these coordinates out of a GNSS but I can’t find the way to convert them to use in the GCP Interface. (been trying for half a day now…)
This is what I got: (one line)

|Comment|GNSS Height|Vert Prec|Horz Prec|Std Dev|Latitude|Longitude|
|beek1|68,33|0|0|0,00742|50 53 40,778276300 +|4 44 14,896675696 +|

This is an example of where I want to go:
+proj=utm +zone=37 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs
gcp01 529356.250827686 9251137.5643209 8.465
gcp02 530203.125367657 9250140.80991621 15.781

I can’t convert these 50 53 40,778276300 + 4 44 14,896675696 + coordinates to UTM,
only Convert Coordinates
seems to accept this format, but the UTM coordinates that it converts to don’t work in the control point file.

Could someone show me the way? (and explain me why the ‘+’)

Thank you so much :slight_smile:

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Welcome!

Can you tell us what GNSS you were using, and what mode or what CRS it was set to record into? Most default to WGS84 of some sort, unless it has been configured for a more precise local CRS/datum combination.

Thank you for your reply :slight_smile:

It’s a Trimble Geo7X cm precision.
Coordinate System: Belgium
Zone: Lambert 72 (correctiongrid) HBG18

Does this answer your question?

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It certainly helps!

Do you have them in a geodata format, like shp or gpkg?

I’m curious about them, and to be honest, don’t have much experience with using GCPs in WebODM.

Shp

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You’ll have to enable sharing outside of your organization, or host that file somewhere else with public sharing.

Sorry, please try this:

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In the meantime I found a website where I can convert the coordinates:

Screenshot 2021-03-12 at 14.01.59

But when I can’t find how to put these coordinates in the correct format for the requested file, this is where I am now:

+proj=utm +zone=31u +north +ellps=WGS84 +datum=WGS84 +units=m +no_defs
gcp01 5639499 622220 66,62

When I load this file in the GCP Editor, the point is somewhere close to Las Palmas :)))

And when I check http://epsg.io/ for zone 31, its in Norway…
So confusing…
I thought people were the most complicated on earth, this is worse lol

2 Likes

Who is preparing your geodata? None of those have PRJ (projection files) that define their CRS.

You probably want US style decimals:

gcp01 5639499 622220 66.62
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Now I’m getting somewhere.
I should have seen that… :man_facepalming:

THANK YOU SO MUCH !

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One more thing about gcp selection.
Is it necessary to select all possible gcp’s in every picture or are 3 pictures per gcp sufficient?
I also have some pictures with 2 gcp’s in, do I select them both or just one?

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Piero had some good guidance here:

I don’t believe it will be a problem to tag multiple GCPs in a single photo, but I may well be wrong. Maybe someone else who has used them more can offer help.

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Multiple tags in single photos are just fine, perhaps even beneficial.

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