creating an orthomosaic from a aerial Lidar capture mission

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

I am trying to determine our mission planning parameters for our lidar flights so that we can allow for the generation of a quality orthomosaic in Pix4D Mapper. to raytrace colourise a point cloud within the Lidar processing workflow we only need a 20% to 50% image overlap (overlap as more to to with strip alignment and vertical coverage than actual image overlap) . However, for orthomosic creation in P4D we obviously need 80%. I believe there is a workflow in P4D that allows for the import of the UAV lidar generated colourised point cloud into P4D replacing the stage 2 processing exercise, allowing us to work with say, a 50% overlap only for images, then continuing onto step 3 for the orthomosaic creation Thus if I can understand the P4D workflow I can ensure the lidar mission planning is suitable for all steps of the post processing process.

2

Hi John,

Welcome to our community!

Could this be the workflow you are looking for?

Article: How to import a Point Cloud delivered by an External Source into PIX4Dmapper for processing

When importing a LiDAR point cloud generated by the external source please keep in mind the followings:

  • Before importing the point cloud, you need to create a project and process Step 1. Initial Processing.
  • The external point would’s coordinate system needs to be the same as the output coordinate system.
  • The point cloud generated by PIX4Dmapper and the external point cloud should be aligned.
    Mark common GCPs in both the model generated by Pix4Dmapper and the external point cloud to align them. If this is not possible, extract points from the Pix4Dmapper model and mark them as GCPs in the external point cloud: How to align projects.
  • If the external point cloud is a DTM, the Orthomosaic may present distortions.
  • All imported points will be treated as a unique group meaning that if the external point cloud is classified (e.g. some points have a terrain or object label), Pix4Dmapper will not take the classification into account. If only points corresponding to the terrain class are imported then the DTM will be generated accordingly.
  • The imported Point Cloud can not be used to generate a 3D textured mesh.

Also if you are unable to import, it could be due to the size. Because the limit of the imported point cloud depends on the RAM size.

I hope this helps.

Best regards,
Rosana (she/her)

3

Thank you!
that goes a long way to getting this resolved.
one outstanding question. What is the minimum overlap needed by pix4d to allow for a quality Orthomosaic to be created, assuming a colourised point cloud is being imported?

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Hi @uav10

We suggest you start with 80% overlap, and beyond that should be tested.

Have a very nice day!

Best regards