# Ground measurements with the Pix4d MeshMapper

**URL:** <https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813>\
**Category:** PIX4Dmapper Questions/Troubleshooting\
**Created:** [July 12, 2015, 10:22pm UTC](https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813 "2015-07-12T22:22:02Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![sean\_bodden](https://avatars.discourse-cdn.com/v4/letter/s/7feea3/32.png) [@sean\_bodden](https://community.pix4d.com/u/sean_bodden)\
**Post date:** [July 12, 2015, 10:22pm UTC](https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813/1 "2015-07-12T22:22:02Z")

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Hi All,

I’m testing the meshmapper app with pix4d pro to identify accuracy with my dji phantom vision 2+. The stitching seems accurate, however, the surface that’s supposed to be only 3’ above sea level is starting at 10metres. Any suggestions as to why this may be happening? Also, how do I change it from metric to imperial?

Thanks,

Sean B

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**Author:** ![Fay\_king](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/fay_king/32/412_2.png) [@Fay\_king](https://community.pix4d.com/u/Fay_king)\
**Post date:** [July 13, 2015, 7:32pm UTC](https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813/2 "2015-07-13T19:32:32Z")

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Did you use Ground Control Points?  
A 10 meter elevation inaccuracy would not shock me if Pix4d only has the geolocation info from the Phantom EXIF data, and no GCP’s. The problem is likely input, not output.

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**Author:** ![Marc\_Desgroseilliers](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/marc_desgroseilliers/32/187_2.png) [@Marc\_Desgroseilliers](https://community.pix4d.com/u/Marc_Desgroseilliers)\
**Post date:** [October 14, 2015, 2:30pm UTC](https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813/3 "2015-10-14T14:30:07Z")

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Indeed, this is within the expected range, especially if the image geolocation is not very precise. One more thing to keep in mind is that in general, the vertical accuracy is not as good as a the horizontal accuracy.

Adding GCPs would certainly help add precision and would probably solve this problem. The precision of the GCPs would have a direct influence on the precision of the output.&nbsp;

[https://support.pix4d.com/hc/en-us/articles/202558699](https://support.pix4d.com/hc/en-us/articles/202558699)

To use imperial unit, one should select a coordinate system in feet. You can see how to do this in this article

[https://support.pix4d.com/hc/en-us/articles/202560439](https://support.pix4d.com/hc/en-us/articles/202560439)

We hope this helps,

Best regards,

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**Author:** ![michael\_duva](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@michael\_duva](https://community.pix4d.com/u/michael_duva)\
**Post date:** [April 4, 2017, 9:22am UTC](https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813/4 "2017-04-04T09:22:19Z")

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hi folks !  
can i render in cloud  
then. open file on desktop.  
then input a ground 2d linear measurement?  
ie. the roof is 23 feet. not 22 feet.  
then. render again ? would entire ortho and or model scale ?

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**Author:** ![Julie\_Pichon](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/julie_pichon/32/592_2.png) [@Julie\_Pichon](https://community.pix4d.com/u/Julie_Pichon)\
**Post date:** [April 5, 2017, 9:14am UTC](https://community.pix4d.com/t/ground-measurements-with-the-pix4d-meshmapper/4813/5 "2017-04-05T09:14:39Z")

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HI Michael,

You can indeed, render in cloud and then[export the results](https://support.pix4d.com/hc/en-us/articles/115000707003) to your desktop. Then you can add a [scale constraint](https://support.pix4d.com/hc/en-us/articles/205360375) to the model in the rayCloud and [upload](https://support.pix4d.com/hc/en-us/articles/202558589) back to our cloud.

The scale constraint will be effective and taken into account because it is coded in the project file (.p4d) sent to our servers for processing.

Regards,