# Accuracy RMS error **URL:** \ **Category:** PIX4Dmapper Questions/Troubleshooting\ **Created:** [December 4, 2021, 7:23am UTC](https://community.pix4d.com/t/accuracy-rms-error/20690 "2021-12-04T07:23:11Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![himalay24sharma](https://avatars.discourse-cdn.com/v4/letter/h/9fc348/32.png) [@himalay24sharma](https://community.pix4d.com/u/himalay24sharma)\ **Post date:** [December 4, 2021, 7:23am UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/1 "2021-12-04T07:23:11Z")
![Capture](https://global.discourse-cdn.com/pix4d/original/2X/5/52d856388cbfc6485c82583c5cc93b4820548136.jpeg) What is the meaning of RMS Error is this related to respected axis accuracy overall or what? if not than how to check the accuracy of the data? ---
**Author:** ![Daniele\_Lecci](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/daniele_lecci/32/9493_2.png) [@Daniele\_Lecci](https://community.pix4d.com/u/Daniele_Lecci)\ **Post date:** [December 7, 2021, 11:13am UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/2 "2021-12-07T11:13:10Z")
Hi @himalay24sharma, Welcome to the Pix4D Community 😉. The mean RMS error you see at the top of your quality report is a mean of the RMS error in the 3 directions (X, Y and Z). > **[Quality report specifications](https://support.pix4d.com/hc/en-us/articles/202558679-Quality-report-specifications#label02)** > >   > >   > > Important: > > For a detailed description of how to analyze the Quality Report: Quality Report Help. > For a description of how to analyze the Quality Report: Step 4. Processing. > > > > The Quality Re... ![2021-12-07_12-10-48](https://global.discourse-cdn.com/pix4d/original/2X/e/e920997b736d72d118077931248b7799b5b1e553.jpeg) Regarding the Root Mean Square error in each direction, you can find more information here: > **[How are tie points errors defined - Mean, Sigma, RMS?](https://support.pix4d.com/hc/en-us/articles/203604125-How-are-tie-points-errors-defined-Mean-Sigma-RMS)** > > The following errors for the Ground Control Points (GCPs) and Checkpoints (CPs) in photogrammetry project are calculated: > > > Mean: The average error in each direction (X,Y,Z). > > Sigma: The standard d... I hope this helps you Cheers ---
**Author:** ![himalay24sharma](https://avatars.discourse-cdn.com/v4/letter/h/9fc348/32.png) [@himalay24sharma](https://community.pix4d.com/u/himalay24sharma)\ **Post date:** [December 9, 2021, 4:37am UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/3 "2021-12-09T04:37:11Z")
still, I am confused how to check the error of the data or is that RMS error in the report showing error in GCP lying on the ground? than what will be the best option to check the error in the data? ---
**Author:** ![Daniele\_Lecci](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/daniele_lecci/32/9493_2.png) [@Daniele\_Lecci](https://community.pix4d.com/u/Daniele_Lecci)\ **Post date:** [December 9, 2021, 8:27am UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/4 "2021-12-09T08:27:21Z")
Hi @himalay24sharma, The RMS will give you the statistical error. If you want to assess the absolute accuracy of the model, you need to use Checkpoints (CP). You can find more information here: > **[Tie points in photogrammetry project (ATP, GCP, MTP, and CP)](https://support.pix4d.com/hc/en-us/articles/115000140963-Tie-points-in-photogrammetry-project-ATP-GCP-MTP-and-CP#CPs)** > > GCPs and MTPs are used to improve the absolute and relative accuracy of photogrammetry projects while Checkpoints are used for quality assessment. ATPs are automatically extracted from images in th... ---
**Author:** ![sunding](https://avatars.discourse-cdn.com/v4/letter/s/90db22/32.png) [@sunding](https://community.pix4d.com/u/sunding)\ **Post date:** [December 10, 2021, 5:05pm UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/5 "2021-12-10T17:05:36Z")
Thank you Daniele, While on this topic, can you explain what actual values are used to calculate this reported RMS? I generally calculate my own by placing check points in my mission area if I care enough about actual accuracy, but I’ve always wondered how Pix4D calculates this RMS. ---
**Author:** ![Daniele\_Lecci](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/daniele_lecci/32/9493_2.png) [@Daniele\_Lecci](https://community.pix4d.com/u/Daniele_Lecci)\ **Post date:** [December 13, 2021, 1:07pm UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/6 "2021-12-13T13:07:11Z")
Hi @sunding, Thank you for your message This Pix4D Documentation page explains how the RMS is calculated for each direction: > **[How are tie points errors defined - Mean, Sigma, RMS?](https://support.pix4d.com/hc/en-us/articles/203604125-How-are-tie-points-errors-defined-Mean-Sigma-RMS#RMS)** > > The following errors for the Ground Control Points (GCPs) and Checkpoints (CPs) in photogrammetry project are calculated: > > > Mean: The average error in each direction (X,Y,Z). > > Sigma: The standard d... Again, if you want to assess the accuracy of your project, please use checkpoints. ---
**Author:** ![Fred\_Beal](https://avatars.discourse-cdn.com/v4/letter/f/4bbf92/32.png) [@Fred\_Beal](https://community.pix4d.com/u/Fred_Beal)\ **Post date:** [April 24, 2024, 1:25pm UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/7 "2024-04-24T13:25:34Z")
Hello Daniele, What is the actual measurement between the predicted and observed points in the RMSE calculation? Meaning, the Check Point (CP) is the measured position, what is the predicted position? Is it the nearest point in the point cloud or is it the intersection point in a triangular irregular network? ---
**Author:** ![Fred\_Beal](https://avatars.discourse-cdn.com/v4/letter/f/4bbf92/32.png) [@Fred\_Beal](https://community.pix4d.com/u/Fred_Beal)\ **Post date:** [April 24, 2024, 1:33pm UTC](https://community.pix4d.com/t/accuracy-rms-error/20690/8 "2024-04-24T13:33:17Z")
\*observed …Meaning, the Check Point (CP) is the measured (observed) position, what is the predicted position?..