Support Website Contact Support Blog

Need Help - Great Coverage w/ High Error?

Been using the software for a few years and like it.  Recently conducted a flight and captured imagery at 80% forward 70% sidelap with a gimbal.  GSD is less than an inch but RMS error on check points is +1.7-FEET?  Also the point cloudy is very noisy - too noisy to convert to a decent CAD file.  I attached a screen shot of the point cloud and the GCP/CGP locations as well as a link to the quality report.

Help would be greatly appreciated.

https://drive.google.com/open?id=1E5gKzKWSNi4d7e280DltWi5LZMZ9LAjs 

 

Hello James,

I would check the following:

  • Are your GCPs and checkpoints given in feet or US survey foot? Please consider that your coordinate system is defined as indicated here. Pix4D is expecting US survey foot

  • Was your flight flown at once? By looking at your Quality Report, I see that although there is only block, there seems to be an area in the middle not so well-connected. I had a similar case some days ago and all of the points (GCPs and checkpoints) fit after processing each day independently. For one reason or another, the internal camera parameters changed from one flight to another (maybe it was hit accidentally or who knows) and it was necessary to define two different cameras (one for each flight).

  • The GCP accuracy is set to 0.02 feet. I would say that is too low. The lower the accuracy you set up, the more weight the GCPs will have in the computation. If the accuracy is overestimated, the block can have tensions. Setup the most realistic accuracy considering not only the measurement in the field but also the manual measurement in the software. For example, if the images are blurring, you cannot expect too much accuracy when measuring in the images.

I hope this information helps you.