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topography troubleshooting

Hello everyone,

I have been tasked by my company to test Pix4d to determine if this technology is something that will be useful for our company. We will primarily be using this technology to create elevated topographys for earthwork estimating/ design purposes. After watching a few webinars I went out and used a Phantom 3 to capture an area that has changed since the last manual topo was generated. there is a road to the east side that is easily recognizable, and should not have changed. After processing with 5 survey grade gcp’s, the road is off by up to 3 feet in some areas(elevation wise). What are some things I can trouble shoot that might be affecting my map? I would think that if everything was correct, that the road should be within a few inches of the old topo.


Thanks in advance,



What did the quality report say?  You may not have had sufficient overlap.  

Also, you do need GCP’s outside the survey area to nail down the edges of the model (model perimeter can still bowl if it’s outside the GCP area).    

Another thought is can you confirm the manual topo and your GCP’s are the exact datum?

You should be able to reproduce elevation results within (2-3X) your model’s resolution.