GCP Interface


#1

Hello, I have searched the forum but did not find any help. I am having trouble exporting a GCP file from the interface and finding it hard to understand what I am doing wrong :slight_smile: All help is appreciated…

So if I understand it correctly you need a minimum of 15 references in 3 (5 ref point in each?) or more photos to create a good/accurate GCP file. So before my missions I marked 6 GCPs on the ground and flew a couple of missions that generated 100 - 200 photos for each mission.

I have a Trimble Juno T41 and did all the measurements for the 6 GCPs with this unit.

First of all I tried looking for high-contrast objects in the mission images and the interface map as suggested, the problem with this is that I usually work were buildnings are few in numbers and also high-contrast objects can be hard to find. But I marked my mission images (5 ref points in each) and then marked them as accurate I could in the map. I did so in three different images from a singles mission.

GCP_1
GCP_2

I assume I am doing something wrong. It did not generate a GCP file.

I would like to mark the GCPs with my dGPS measurements for better accuracy. If I understand it correctly I will need to upload all the mission images were you can see my GCPs on the ground (the more images you mark/ref the better accuracy on the GCP file??).
I will need to mark/lock the refpoints (GCPs) in the interface/mission images and add the coordinates in “custom mode” in the interface map?? Can somebody please give me some tips on how to do this, I do not get this to work - and the most important, is it meant to work like I am trying to explain :slight_smile: ??
With this method I will introduce 1 reference point in the gcp interface to each mission image that have the visiable GCP on the ground. Off-course i will need to create atleast 15 different points to 15 different mission images, and as mentioned before - more reference point = better GCP file. Do I undestand this correctly.

GCP_3

Please help a webodm/GCP beginner :slight_smile:


#2

Can you paste the coordinates file you used for the map coordinates?


#3

Hi @mattias, you’ll need to lock each of the points to their respective points on the opposite side. They are locked to each other when they both turn green and when you mouse over one, and it highlights the one on the opposite side.


#4

Thanks alot for your input. I think my question is more realated to the (my) workflow in the GCP interface.

@dakotabenjamin this is the GCPs I need to use with this mission. I added 1 1 image.JPG to get the interface to add my points in the map.

WGS84 UTM 33N
592836 6582077 62.396884 1 1 1.JPG
592844 6582090 62,277474 1 1 2.JPG
592839 6582058 65.513986 1 1 3.JPG
592860 6582022 70.642407 1 1 4.JPG
592880 6582051 68.319541 1 1 5.JPG
592866 6582075 65.551683 1 1 6.JPG

Instead of adding the points to the map via the method above, I would like to add only images, then find my GCP in the uploaded image/s and then write the correct XYZ in the custom window, press apply and have a point to push/relate the point in the image. But maybe this is not the way it is suppose to work?

I did process the images without GCPs, I ended ut with an xy error of 0,6-2,3 meters for the 6 GCPs. Is that a normal error?

GCP_1

I then uploaded my images and found my GCPs in my imaged and ref. them to the GCP_list points in the map.

GCP_2

I ended up with 20 images (5 "images from the gcp_list) and 15 correctly ref with GCP points in image and map. I was not able to take away the “images” generated from the gcp_list. I exported the file.

GCP_3
GCP_4

I erased the “gcp_list” points and as you can see - no Z-value followed from the points, and all were set to 0.

GCP_5

I did need to add the correct z-value to the gcp_list. I am at the moment processeing the same images WITH the gcp_list.

Obviously I am doing something wrong, I can not figure out how to add the correct xyz point to the map to be able to ref it to the gcp point in the image.

Regards Mattias


#5

If I understand correctly, you have your correct locations and want to apply those geographic locations to the image locations.

If so, the format for your input should be similar to as follows: https://github.com/OpenDroneMap/odm_data_copr/blob/master/gcp_list_noimg.txt


#6

Hi @smathermather-cm, thanks for your reply.

Yes - you understand it correctly. I am trying to create a .txt file like yours.

  1. The interface will not load the points and will not load the file.

EPSG:32633
gcp01 592836 6582077 62.396884
gcp02 592844 6582090 62.277474
gcp03 592839 6582058 65.513986
gcp04 592860 6582022 70.642407
gcp05 592880 6582051 68.319541
gcp06 592866 6582075 65.551683

  1. The interface will accept/load the file but not project/show the points.

WGS84 UTM33N
gcp01 592836 6582077 62.396884
gcp02 592844 6582090 62.277474
gcp03 592839 6582058 65.513986
gcp04 592860 6582022 70.642407
gcp05 592880 6582051 68.319541
gcp06 592866 6582075 65.551683

  1. The interface will load and show the points, but only display gcp01 and gcp03. ??

+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
gcp01 592836 6582077 62.396884
gcp02 592844 6582090 62.277474
gcp03 592839 6582058 65.513986
gcp04 592860 6582022 70.642407
gcp05 592880 6582051 68.319541
gcp06 592866 6582075 65.551683

  1. The interface will load and show all the points correctly - but z = 0?

+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
gcp01 592836 6582077 0
gcp02 592844 6582090 0
gcp03 592839 6582058 0
gcp04 592860 6582022 0
gcp05 592880 6582051 0
gcp06 592866 6582075 0

Why can you not assign z to the gcp_list ? Or am I missing/not understanding something?

//Mattias


#7

Hmm, this seems like a bug (or two). Can you create an issue here: https://github.com/posm/posm-gcpi/issues ?

Thanks!


#8

Hello, yes I will post it there. Thanks.


#9

Link back to issue: https://github.com/posm/posm-gcpi/issues/41