# Unsupported geoid model workflow

**URL:** <https://community.pix4d.com/t/unsupported-geoid-model-workflow/20923>\
**Category:** PIX4Dmapper\
**Created:** [December 31, 2021, 6:43pm UTC](https://community.pix4d.com/t/unsupported-geoid-model-workflow/20923 "2021-12-31T18:43:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![h20robotics376](https://avatars.discourse-cdn.com/v4/letter/h/7ea924/32.png) [@h20robotics376](https://community.pix4d.com/u/h20robotics376)\
**Post date:** [December 31, 2021, 6:43pm UTC](https://community.pix4d.com/t/unsupported-geoid-model-workflow/20923/1 "2021-12-31T18:43:49Z")

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So I’m pretty new to this, but have run into a few issues already getting accurate Z from my checkpoints. We did a 160ha scan where gcp’s couldn’t be placed except on the first third of the Eastside. Knowing this would introduce errors I just laid out targets on the East for checkpoints. The GPS was processed in PPK mode, but now I need to apply the orthometric heights from ellipsoid to the images. Not too bad except my pos files aren’t in csv, but that’s for another topic. Once these images are in orthometric height, what do you select for a vertical coordinate system? Images, checkpoints and output should all be arbitrary?

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**Author:** ![Alice\_Bonfiglio](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/alice_bonfiglio/32/291_2.png) [@Alice\_Bonfiglio](https://community.pix4d.com/u/Alice_Bonfiglio)\
**Post date:** [January 4, 2022, 10:14am UTC](https://community.pix4d.com/t/unsupported-geoid-model-workflow/20923/2 "2022-01-04T10:14:22Z")

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Hi @h20robotics376 ,

What you say is correct. The **vertical** image, checkpoints and output coordinate system should be set to arbitrary in PIX4Dmapper, so that [no conversion will occur](https://support.pix4d.com/hc/en-us/articles/202558239-Select-Image-GCP-Output-Coordinate-System#label12).

For more information:

> **[How to define Pix4D outputs with respect to a Geoid model](https://support.pix4d.com/hc/en-us/articles/360021076212-How-to-define-Pix4D-outputs-with-respect-to-a-Geoid-model)**
>
>  
> 
> Video: Watch the instructional video related to Altitude and Vertical Coordinate System: here.
> 
> The Z coordinate (altitude) can be given with respect to an ellipsoid (ellipsoidal height)  or wit...

I would also suggest you reading the following Community post:

> [@Horizontal grid corrections and transformations](https://community.pix4d.com/t/horizontal-grid-corrections-and-transformations/3325):
>
> Hi all, Update 1/5/2021: [Pix4Dmatic](https://www.pix4d.com/product/pix4dmatic-large-scale-photogrammetry-software) supports the most common horizontal grid corrections and transformations. The corrections will be used automatically based on the selected coordinate systems. More in the [How to use coordinate systems in Pix4Dmatic](https://support.pix4d.com/hc/en-us/articles/360045578171-How-to-use-coordinate-systems-in-Pix4Dmatic#Horizontal_grid_corrections_and_transformations) article. To use horizontal grid corrections and transformation in Pix4Dmapper, see the workaround mentioned below. If a horizontal coordinate system transformation is required to accurately transform your project’s Image Geolocation Coordinate …

Cheers