Problems with gcp help!

WebODM
,
#1

@pierotofy
@SaijinNaib

Hello friends , im having issues with the final result of the orthophoto,the final result is out of position, and is not matching with the gcp, it has a displacement between 4 and 7 meters,
im not sure if i have to change something with the configuration, or something else
this are my gcp

WGS84 UTM 17N
642376.099 985011.667 17.369 5472 3078 DJI_1492.JPG
642376.099 985011.667 17.369 5472 3078 DJI_1530.JPG
642376.099 985011.667 17.369 5472 3078 DJI_1680.JPG

642364.573 984781.589 21.370 5472 3078 DJI_1368.JPG
642364.573 984781.589 21.370 5472 3078 DJI_1468.JPG
642364.573 984781.589 21.370 5472 3078 DJI_1554.JPG

642494.661 984640.211 18.754 5472 3078 DJI_877.JPG
642494.661 984640.211 18.754 5472 3078 DJI_939.JPG
642494.661 984640.211 18.754 5472 3078 DJI_1035.JPG

642540.891 984428.860 12.576 5472 3078 DJI_51.JPG
642540.891 984428.860 12.576 5472 3078 DJI_618.JPG
642540.891 984428.860 12.576 5472 3078 DJI_748.JPG

642311.671 984373.747 13.239 5472 3078 DJI_1243.JPG
642311.671 984373.747 13.239 5472 3078 DJI_1413.JPG
642311.671 984373.747 13.239 5472 3078 DJI_1425.JPG

642720.272 984459.399 16.774 5472 3078 DJI_290.JPG
642720.272 984459.399 16.774 5472 3078 DJI_370.JPG
642720.272 984459.399 16.774 5472 3078 DJI_383.JPG

642848.071 984609.716 16.332 5472 3078 DJI_502.JPG
642848.071 984609.716 16.332 5472 3078 DJI_559.JPG
642848.071 984609.716 16.332 5472 3078 DJI_478.JPG

642645.423 984604.972 27.354 5472 3078 DJI_82.JPG
642645.423 984604.972 27.354 5472 3078 DJI_153.JPG
642645.423 984604.972 27.354 5472 3078 DJI_201.JPG

thanks for the help

1 Like
#2

A quick observation. All of the photo coordinates in your GCP file are the exact same coordinates 5472 3078. They should be unique numbers corresponding to the location of the image of the GCP in each photo

2 Likes
#3

those are the pixel size, they must be equal

1 Like
#4

You are correct that they refer to pixels, but it is the position, in x,y pixels, of the GCP in that specific .jpg image. When using either of the two GCP interfaces to create gcp.txt, it retreives the x,y position, in pixels, of the point you tag. See below:

GCP file format:

geo_x geo_y geo_z im_x im_y image_name [gcp_name] [extra1] [extra2] …

Example:

+proj=utm +zone=10 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
544256.7 5320919.9 5 3044 2622 IMG_0525.jpg 544157.7 5320899.2 5 4193 1552 IMG_0585.jpg 544033.4 5320876.0 5 1606 2763 IMG_0690.jpg

More details are available here:

https://docs.opendronemap.org/gcp/

It took me several tries to finally create a working gcp.txt file.

3 Likes