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Pix4d GCP errors show small errors but orthomosaic ground targets and gcp coordinates are far apart when exported to ArcMap


I processed my imagery (~2000 images) with my GCPs input into Pix 4D, and I found myself getting pretty small Geolocation errors (x,y)(less than 5 cm RMS in the quality report), and the GCPs lining up really well with the the center of my visual targets shown on the interface for my processed 3d model. However, when I load my exported Pix4D-made orthomosaic and my GCPs into my ArcMap 10.4 for other processing, my ground targets that I can see in my orthomosaic are over half a meter away from my marked GCPs. What’s going on here? I feel like my entire orthomosaic shifted one direction about 0.7 meters, and now I can’t do the ArcMap processing that I needed with a reliable orthomosaic. I already made sure that everything was in the proper coordinate system and projection in both softwares, so that’s not the issue.


Any advice? 

Hi Colby,

It could have something to do with the coordinates systems that were selected in Pix4Dmapper and in ArcMap 10.4. Could you give us some more information about the coordinate systems you selected in both software (name, EPSG code, .prj)?

Are the coordinate systems of the GCPs and the outputs the same?

Is this an issue that you experienced with multiple projects?


Hi there, 

In Pix4Dmapper all of my GCPs are in WGS 84 / UTM  zone 17N (egm96). The output coordinate system is set to WGS 84/ UTM zone 17N (egm 96) as well.

In ArcMap I have my data frame and GCP shapefile both projected in WGS 84 / UTM Zone 17 N, as well as the orthomosaic. I don’t think that that is the problem. So far this is the only data set I have fully processed so I am not sure if my other three projects will have the same problem once I finish them.