# What does step 2. Point Cloud and Mesh do? and What does step 3. DSM Orthomosaic and Index do?

**URL:** <https://community.pix4d.com/t/what-does-step-2-point-cloud-and-mesh-do-and-what-does-step-3-dsm-orthomosaic-and-index-do/6461>\
**Category:** PIX4Dmapper Questions/Troubleshooting\
**Created:** [May 2, 2018, 2:30pm UTC](https://community.pix4d.com/t/what-does-step-2-point-cloud-and-mesh-do-and-what-does-step-3-dsm-orthomosaic-and-index-do/6461 "2018-05-02T14:30:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![guan\_guan](https://avatars.discourse-cdn.com/v4/letter/g/82dd89/32.png) [@guan\_guan](https://community.pix4d.com/u/guan_guan)\
**Post date:** [May 2, 2018, 2:30pm UTC](https://community.pix4d.com/t/what-does-step-2-point-cloud-and-mesh-do-and-what-does-step-3-dsm-orthomosaic-and-index-do/6461/1 "2018-05-02T14:30:07Z")

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Hi, guys. I knew pix4d mapper have been image processed automatically by step and step.&nbsp;

But I still want to learn more about What does step 2. Point Cloud and Mesh do? and What does step 3. DSM Orthomosaic and Index do?

What **Photogrammetry principles** do Step 2 and Step 3 separately use?

&nbsp;

Thanks very much.

Best wishes.

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**Author:** ![momtanu.chakraborty](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/momtanu.chakraborty/32/269_2.png) [@momtanu.chakraborty](https://community.pix4d.com/u/momtanu.chakraborty)\
**Post date:** [May 9, 2018, 12:16am UTC](https://community.pix4d.com/t/what-does-step-2-point-cloud-and-mesh-do-and-what-does-step-3-dsm-orthomosaic-and-index-do/6461/2 "2018-05-09T00:16:13Z")

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Hi Guan,

In step 2 the automatic tie points created from step 1 are used for point&nbsp;cloud densification.&nbsp;The dense point Cloud is then used to generate a surface composed of&nbsp;triangles which is the mesh.

Step 3 creates a DSM based on the densified point cloud. The orthomosaic is also generated in this step taking the DSM and point cloud as input.&nbsp;The creation of the Orthomosaic is based on orthorectification. This method removes the perspective distortions from the images. You can have a look at this link:&nbsp;[https://support.pix4d.com/hc/en-us/articles/115002495706-Processing-steps](https://support.pix4d.com/hc/en-us/articles/115002495706-Processing-steps)

Regards,

Momtanu