# Problems with altitude values in DTM **URL:** \ **Category:** PIX4Dmapper Questions/Troubleshooting\ **Created:** [June 14, 2016, 6:53pm UTC](https://community.pix4d.com/t/problems-with-altitude-values-in-dtm/5422 "2016-06-14T18:53:14Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![xavi\_Rodriguez](https://avatars.discourse-cdn.com/v4/letter/x/ed8c4c/32.png) [@xavi\_Rodriguez](https://community.pix4d.com/u/xavi_Rodriguez)\ **Post date:** [June 14, 2016, 6:53pm UTC](https://community.pix4d.com/t/problems-with-altitude-values-in-dtm/5422/1 "2016-06-14T18:53:14Z")
Hi, I´m trying to generate a MDT with PIX4D, I´m using a Phantom 3 Advanced. I´ve a problem with the altitude values. First the program gave me values from -17 to 3 meters without GCP, and values go between 2 meters and 33 meters with GCP. Thanx Xavi   ---
**Author:** ![system](https://global.discourse-cdn.com/pix4d/original/2X/7/7ab5ac5783ad6a7d04ca921ff5cbb2f02ad6ca6a.png) [@system](https://community.pix4d.com/u/system)\ **Post date:** [June 16, 2016, 12:19pm UTC](https://community.pix4d.com/t/problems-with-altitude-values-in-dtm/5422/2 "2016-06-16T12:19:56Z")
Hi, My understanding is that it’s a firmware issue of DJI. I’ve seen several posts on other website explaining that DJI writes elevation above see level but there is an error of several meters. I did missions and got different altitude values whereas I was flying the exact same area with the same drone. In my case, using ground control points solved the problem but for sure the vertical coordiantes of DJI is not reliable entirely let’s say 😕 ---
**Author:** ![system](https://global.discourse-cdn.com/pix4d/original/2X/7/7ab5ac5783ad6a7d04ca921ff5cbb2f02ad6ca6a.png) [@system](https://community.pix4d.com/u/system)\ **Post date:** [June 16, 2016, 12:21pm UTC](https://community.pix4d.com/t/problems-with-altitude-values-in-dtm/5422/3 "2016-06-16T12:21:37Z")
I’ve just found a post on the forum addressing that issue: [https://community.pix4d.com/t/5238](https://community.pix4d.com/t/5238)