# High RMS error using GCPS **URL:** \ **Category:** PIX4Dmapper Questions/Troubleshooting\ **Created:** [July 11, 2023, 3:06am UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063 "2023-07-11T03:06:23Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Renato](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/renato/32/7311_2.png) [@Renato](https://community.pix4d.com/u/Renato)\ **Post date:** [July 11, 2023, 3:06am UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063/1 "2023-07-11T03:06:23Z")
Hi guys, I was testing the example projects from pix4dmapper, especifically the Quarry one, but I got high erros in my absolute geolocation. Why is my absolute RMS error so high even though I added GCPs? Did I mark them wrong? In order to check for accuracy I should check the RMS error in the absolute geolocation section, correct? I attached the final report down below: [Pedreira\_report.pdf](https://community.pix4d.com/uploads/short-url/dgZmwrRBVaMTqSaF83HlCPQBLXd.pdf) (2.0 MB) I appreciate any help. Have a great day! ---
**Author:** ![tibor.vari](https://avatars.discourse-cdn.com/v4/letter/t/db5fbb/32.png) [@tibor.vari](https://community.pix4d.com/u/tibor.vari)\ **Post date:** [July 12, 2023, 10:02am UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063/2 "2023-07-12T10:02:51Z")
As far as I can see there is nothing wrong with the result. The biggest Error X/Y[m] for the Ground Control Points is less than 23mm. Just fine. Error Z[m] of 129mm is not outrageous either. The Geolocation Bias -0.331006(X) 0.588261(Y) 0.072632(Z) is just a shift, a translation between initial and computed image position in the output coordinate system. ---
**Author:** ![Renato](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/renato/32/7311_2.png) [@Renato](https://community.pix4d.com/u/Renato)\ **Post date:** [July 13, 2023, 1:13pm UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063/3 "2023-07-13T13:13:36Z")
Thank you for your reply! Do you know how reliable is the accuracy in the quality report when using NTRIP or GCPs? Are they approximations? Thank you in advance! ---
**Author:** ![Mike\_K](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/mike_k/32/4697_2.png) [@Mike\_K](https://community.pix4d.com/u/Mike_K)\ **Post date:** [July 19, 2023, 9:57pm UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063/4 "2023-07-19T21:57:49Z")
Hi Renato, Mapper will calculate the errors to the GCPs. These are not approximations but very reliable numbers. As for the NTRIP, these will correct relative to the closes basestation. Typically a rover should be able to acquire a point that is 2-3cm. However, there are many factors that can impact the accuracy such as the distance to the nearest basestation (amongst others). ---
**Author:** ![Renato](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/renato/32/7311_2.png) [@Renato](https://community.pix4d.com/u/Renato)\ **Post date:** [July 24, 2023, 12:10am UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063/5 "2023-07-24T00:10:53Z")
Hi Mike, thanks for replying to my post. I did a test with a mini 2 and the results for absolute Geolocation RMS error in the final report is x=86,7 cm, y=89,6 cm and z=63,91 cm. I have attached the final report below: [Galpao\_mini\_rapid\_report.pdf](https://community.pix4d.com/uploads/short-url/y9Z6n67gXwEWO0i1dJrEsct1oKI.pdf) (2.1 MB) Even though the GNSS receiver on the drone may generate meters of error. Could I say those measurements have been ajusted and are reliable without GCPs on the final report above? Second question, If I add GCPs or an RTK module with Ntrip and they show a RMS error of just a few centimeters (3-10cm) after processing, could I tell my client that this is the error if he makes any measurements in my model? Thank you for time helping me understand the final report. Have a great day! ---
**Author:** ![Mike\_K](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/mike_k/32/4697_2.png) [@Mike\_K](https://community.pix4d.com/u/Mike_K)\ **Post date:** [July 24, 2023, 7:47pm UTC](https://community.pix4d.com/t/high-rms-error-using-gcps/27063/6 "2023-07-24T19:47:38Z")
If the drone is not RTK and you do not have GCPs, then you cannot assess the accuracy. If you have GCPs and your RMS error is 3-10cm then you can tell your client that the model is reliable within these tolerances.