# GCPs, good horizontal bad vertical **URL:** \ **Category:** PIX4Dmapper\ **Created:** [September 27, 2022, 2:07am UTC](https://community.pix4d.com/t/gcps-good-horizontal-bad-vertical/24055 "2022-09-27T02:07:04Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![jlmitchell42](https://avatars.discourse-cdn.com/v4/letter/j/82dd89/32.png) [@jlmitchell42](https://community.pix4d.com/u/jlmitchell42)\ **Post date:** [September 27, 2022, 2:07am UTC](https://community.pix4d.com/t/gcps-good-horizontal-bad-vertical/24055/1 "2022-09-27T02:07:04Z")
How do I load log file that’s too large? Would like someone to review. ---
**Author:** ![jlmitchell42](https://avatars.discourse-cdn.com/v4/letter/j/82dd89/32.png) [@jlmitchell42](https://community.pix4d.com/u/jlmitchell42)\ **Post date:** [September 27, 2022, 2:33am UTC](https://community.pix4d.com/t/gcps-good-horizontal-bad-vertical/24055/2 "2022-09-27T02:33:44Z")
[Barry Ash 20 September 2022\_report.pdf](https://community.pix4d.com/uploads/short-url/7LrdyrADPhdJNQhdHen214xVxbE.pdf) (2.2 MB) ---
**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:** [September 28, 2022, 8:49pm UTC](https://community.pix4d.com/t/gcps-good-horizontal-bad-vertical/24055/3 "2022-09-28T20:49:46Z")
Hello, I looked at your quality report and I do see the error in the vertical. I would suggest remarking your GCPs. The key to this is to keep your projection error below 1. In your case you have a couple GCPs that probably were not marked very well. ![qr](https://global.discourse-cdn.com/pix4d/original/2X/d/d73050d140ba6609962578deb3fbeb78d220f6d9.png) When you remark I would suggest zooming in to the highest zoom possible ensuring that you are marking the exact pixel. In addition, only mark very best images. If the GCP is a bit blurry, or is at the side of the image I would skip it. Lastly, I would try to mark every GCP with 10-15 images.