# Excluding building footprints from TINs/ Contours in pix4d survey

**URL:** <https://community.pix4d.com/t/excluding-building-footprints-from-tins-contours-in-pix4d-survey/23742>\
**Category:** PIX4Dsurvey Questions/Troubleshooting\
**Created:** [August 30, 2022, 4:58pm UTC](https://community.pix4d.com/t/excluding-building-footprints-from-tins-contours-in-pix4d-survey/23742 "2022-08-30T16:58:18Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![bkzins](https://avatars.discourse-cdn.com/v4/letter/b/7cd45c/32.png) [@bkzins](https://community.pix4d.com/u/bkzins)\
**Post date:** [August 30, 2022, 4:58pm UTC](https://community.pix4d.com/t/excluding-building-footprints-from-tins-contours-in-pix4d-survey/23742/1 "2022-08-30T16:58:18Z")

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I have a point cloud which, after running terrain classification and removing buildings, has holes in the bare earth point cloud where the building footprints are. This is great! However, when I create a TIN and then Contours, the software interpolates between points and fills these foot prints in. Normally this is ideal, but I need to produce contours for a land surveyor that does not want contours running through building footprints. These need to be left as “holes” in the TIN. I can’t figure out how to turn off point interpolation, or if there is another way. Can some one help?

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**Author:** ![Daniele\_Lecci](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/daniele_lecci/32/9493_2.png) [@Daniele\_Lecci](https://community.pix4d.com/u/Daniele_Lecci)\
**Post date:** [September 6, 2022, 1:44pm UTC](https://community.pix4d.com/t/excluding-building-footprints-from-tins-contours-in-pix4d-survey/23742/2 "2022-09-06T13:44:00Z")

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Hi @bkzins,

Thank you for your message and welcome to the Pix4D Community 😉 .

Unfortunately, it is not possible to have holes in the TIN.

However, you can create polylines and/or polygons at building footprints, set these objects at the desired elevation, and use them as break lines as described here:

> **[TIN - PIX4Dsurvey](https://support.pix4d.com/hc/en-us/articles/360046785131-TIN-PIX4Dsurvey#Use_terrain_layers_as_breaklines)**
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> Outlier Filter
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> Terrain filter
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> Grid of points
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> TIN
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> Contour lines
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> The TIN (Triangular Irregular Network) is a seamless set of triangles representing a surface. In PIX4Dsurvey, the TIN...

By doing so, the entire building footprint will be at the same altitude, and no contour will cross the footprint.