# Checkpoint Accuracy for Measurement's

**URL:** <https://community.pix4d.com/t/checkpoint-accuracy-for-measurements/15442>\
**Category:** PIX4Dmapper Questions/Troubleshooting\
**Created:** [November 12, 2020, 3:23am UTC](https://community.pix4d.com/t/checkpoint-accuracy-for-measurements/15442 "2020-11-12T03:23:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jared.sharp](https://avatars.discourse-cdn.com/v4/letter/j/7993a0/32.png) [@jared.sharp](https://community.pix4d.com/u/jared.sharp)\
**Post date:** [November 12, 2020, 3:23am UTC](https://community.pix4d.com/t/checkpoint-accuracy-for-measurements/15442/1 "2020-11-12T03:23:59Z")

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I’m comfortable with importing and using GCP’s and understand how to import a checkpoint. My question is what error range do I use? When I’m using GCP’s and a checkpoint for this small project. What error should I be using. +/- .12 to .31 inches for checkpoint or the RMS error from the GCP’s

 ![image](https://global.discourse-cdn.com/pix4d/original/2X/a/a9ae44a55569a6fa31c1e7d96fe203f5a1ba3730.png) ![GCP from Quality Report](https://global.discourse-cdn.com/pix4d/original/2X/8/800244fe6e11aca34c39a508001ec6bb9436fc69.jpeg)

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**Author:** ![Andrew\_Milanes](https://avatars.discourse-cdn.com/v4/letter/a/a4c791/32.png) [@Andrew\_Milanes](https://community.pix4d.com/u/Andrew_Milanes)\
**Post date:** [November 12, 2020, 2:44pm UTC](https://community.pix4d.com/t/checkpoint-accuracy-for-measurements/15442/2 "2020-11-12T14:44:56Z")

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For a true error estimate you should use RMSe of the checkpoints, not GCPs. I would suggest you collect twice the number of points needed then use half for GCPs and half for check points.