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GCPs & coordinate system

I am currently using V2.0.83 (64 bit). I am experiencing frustrating problems with the GCPs list which I load as a .csv file.

In previous versions, I formatted the GCPs as Lat/Long/Alt (and optionally, precision), using the same coordinate system as in the images EXIF. This worked very well.

But now, the same .csv file stopped working because PIX4D interprets the GCPs coordinates input as meters, i.e. it interprets the numbers as projected coordinates rather than lat/long points.

Digging a little further, I figured out that PIX4D expects the GCP file to be in the same units as the inferred images coordinates system. Follow me on this one… Here is the step-by-step:

a) Load images with the EXIF GPS set as WGS84 (lat/long)

b) From the images, PIX4D finds the UTM projection (18N for example)

c) It now expects the GCPs to be expressed as 18N projections and the drop-down menu for importing GCPs only shows meters or feet. There is no lat/long.

d) The software will still load the csv file, but it will interpret the lat/long from the CSV file as meters, with the result that the GCPs all appear close to Greenwich, England, and this will of course make the software warn you that your GCPs are far outside the area covered by the images.

I found a cumbersome way around the problem. Before loading the GCPs, set the GCPs geo format to arbitrary. You’ll have to find the EPSG number for the datum you used in your images and the GCPs; in the case of WGS84, this would be EPSG 4326. Select this as the arbitrary coor system. As a result, the GCPs table headers now display lat/long and the numbers will be correctly interpreted.

Frederic Charpentier

Experiencing the same issue, version 2.1.47 - output coordinate system is always set to x,y,z coordinate system rather than lat,long.

Cannot find a way to change this for the output coordinate system at the moment, but as in the post above, to allow import of lat,long,alt GCP csv file, in the GCP/MTP manager

 

  1. edit GCP coordinate system

  2. set coordinate system definition to arbitrary, click OK

  3. edit GCP coordinate system again, select know coordinate system, click OK

headers change to lat, long and csv file can be imported.

 

A strange issue, thanks for pointing out the workaround.

 

Charlie

 

I’m having the same problem, but even once I change the coordinate system to arbitrary and then back to the correct system, the headings still say meters. I’m using version 3.2.23. Any suggestions?

Hi, 

As Frederick already mentioned it is possible to import GCPs in latitude/longitude format if you choose the correct coordinate system, e.g. WGS84 (EPSG 4326) in the GCP/MTP Manager. There is no need to set is as arbitrary. 

When you import GCPs in latitude/longitude format they will be shown will only 3 decimals but in fact all decimals are imported. If you close and open the GCP/MTP Manager you will see all decimals. 

Best,