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Close GCP and different Altitude


I have been processing large scale Images along with DTM, DSM and Contours.(Aprox 1,000,000 M²) many have been proceed with a satisfactory result.

But my last product produce a very noticeable difference between the DTM and the Contours, i asked fro help to a GIS expert and he told me some GCP were too close and different Altitude and might cause the software (PIX4D) to get confused.

Is this somewhat true? Does close GCP at different altitude might confuse a Mapping software? 


(In case you Wonder…The two points that seems to be together (532&499) i deleted one of those before processing)

I had the understanding that GCP are absolute, and they are tied to the exact Point they are pointed, not matter how close each other they are. 

My principal goal to have close point at different altitude was to help the software differentiate the changes on elevation.

I would like the support of the software’s Devs and more understanding(than me of course) people, on Mapping/Geo-processing.


Thanks you very much in advance. 



Thanks for explaining the issue. I have some troubles to understand the content of the screenshot. Are these several projects or only one? There are some more visible tiles than others and some areas are blurry. I circled some of the tiles in blue: 

Could it be that there are blurry images in the project? These could be used in the creation of the orthomosaic and create those blurry patches.

Please share the quality report of a project where you had issues between the DTM and the contours. This can be a good first step for the investigation.

Normally, placing GCPs, if they are correctly marked and the accuracy is well defined should not create such issues as they serve as reference. 

Greetings and Thanks for the answer, 


Yess during the flights i had a cloudy day, but since i was schedule to finish i had to make do with that. Most of the orthographic was blurry, i had to fix the key points with mosaic editor, replacing the blurry homes with more clear image.

I believe the issues between DTM and Contours are due to the blurry images, but since some one else blamed the GCP i wanted to find more info. 

I got the Workstation processing another Batch, once done i will upload the report.


Thanks again

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