Accuracy of Image collection with RTK GPS

I collected images from drone : Tarot 650, Cannon S-110 and RTK GPS.

Image data : GSD(094cm/pixel), 36 images

After processing them in Pix4D, the quality report showed the accuracy values like RMS(X=.954, Y=2.542, Z=1.756) which was a quite low accuracy even getting from RTK GPS.

What’s wrong with it?

Hi Kijun,

What is the accuracy of your images’ coordinates? The default accuracy in Pix4Dmepper is 5 and 10 m as you can see in the following screenshot:

When using RTK technology, the images’ accuracy should be much better (few centimeters). Please confirm that the accuracy of your images is set correctly in the Image Properties Editor window.

As a general comment, 36 images is a very small dataset. Smaller datasets are prone to errors. I would recommend you to take a dataset of at least 100 images, so that it is more robust.



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You’re right. I just used the default accuracy when I set up the process. But I’ don’t make sure why it effect on the absolute geolocation. Anyway I try to work with small accuracy input.



If there are no GCPs in the project, the absolute geolocation is taken by the images’ coordinates. The software needs to know how much to trust these coordinates, this is why setting the correct accuracy is important.

Hope it helps :slight_smile:

how can I know the accuracy of my rtk/ppk system? 

Hi Mohammad,

When an RTK GPS is used for the image geolocation, different accuracy values are assigned to the images in order to achieve RTK accuracy for the results.
The manufacturer should assign different accuracy to each image coordinates depending on the number of satellites seen and the corrections applied.The accuracy of the image geolocation is read from the EXIF file of each image and it sets the weight with which each coordinates will be taken into account for processing. 

In case you doubt about the accuracy of your system, the best way to find it out is to check the specification or to consult your GPS manufacturer.


From what I have read on the DJI forums, the RTK data isn’t put into the EXIF as it is just a “flying” tool.  I don’t have RTK yet so I can’t confirm but they do say that post-flight geotagging from the flight log will get the higher accuracy into the pictures.

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