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Height precision in surveys

Since I use Pix4Dmapper each day I’m happier from the facility of managing data in this software, especially points (MTPs or GCPs) and polylines. The only issue its the height precision. We cannot expect that it will give you 1 cm height when your GCPs have 1 cm precision in quality report. You can expect 3 to 8 cm height difference between model and points surveyed in the field.

Another is the positioning of GCPs. You should every 60 to 100 meters have one GCP or Check point to control the quality of your model , or if the area is to small at least 5 GCPs well distributed in the model.

Great peace of software but, steel missing point classification

Good Job everybody in Pix4D and thanks

Hi Jorge,

The distribution of GCPs depends on the project:

It is also important to set correct accuracy values in the GCP/MTP Manager. If the expected vertical accuracy of GCPs is 1cm then you need to change the “Accuracy Vert [m]” to 1cm. More here: https://support.pix4d.com/hc/en-us/articles/202558329

As for your remark about the vertical accuracy. You need to keep in mind that the expected vertical accuracy of outputs is 1-3 times the GSD, e.g. if your GSD is 3cm then the expected vertical accuracy is 3 - 9cm.

Regards,

 

I finished an experiment where I flew a parking lot with my P4P drone 120’ above ground (37m). I did use GCPs. I also independently took 60 shots with survey grade GNSS. I brought the drone survey into AutoCAD and I also brought the 60 points into AutoCAD. The average elevation difference I had with the drone survey and the 60 points was 1.5 cm or 0.05 feet. This is also in the range of the accuracy of the GNSS, so the drone survey might be even better!

I’m very pleased with my choice of using Pix4D. I feel it is the dominant and best software out there for this type of work. 

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