How to correct Building Artifacts in the DSM and Orthomosaic with the rayCloud

 
Note: 
  • The orthomosaic is generated based on the DSM that was created from the Densified Point Cloud. Thereby, errors and noise present in the Densified Point Cloud will be reflected in the orthomosaic. These distortions occur because Orthorectification is used instead of Photo Stitching, for more information: 202558869.
  • When computing the Densified Point Cloud, the altitude of the points will not be perfectly estimated. However, errors and noise can be minimized with datasets that have high overlap, good visual content of the images, GCPs, etc.
  • These errors and noise result in altitude differences for points that are supposed to be at the same altitude: for example points that belong to the same edge of a building. This altitude difference explains the distortions that appear near building edges in the orthomosaic.
 
Important: This method preserves the geometry but requires a certain amount of manual work depending on the amount of objects to correct. Before proceeding with this method, it may help to read these tips to correct artifacts: 202560459.

Planar surfaces can be used to correct the point cloud on building areas:

1. Draw one or several New Surfaces on the roof using the rayCloud202560269.
2. In the sidebar, under the section Selection, select the check box Use for DSM and Triangle Mesh to use the surface for the DSM generation: 202558219.
3. Once the surfaces are created, process step 3. DSM, Orthomosaic and Index again. This will remove the noisy points from the roof and create a DSM and Orthomosaic without artifacts.

See Figure 1. below.

If there is still noise, the noise can be reduced even more by creating surfaces on the ground:

1. Draw one or several New Surfaces on the ground next to the building using the rayCloud202560269.
2. In the sidebar, under the section Selection, select the check box Use for DSM and Triangle Mesh to use the surface for the DSM generation: 202558219.
3. Once the surfaces have been created, process step 3. DSM, Orthomosaic and Index againThis will remove even more noisy points from the roof and create a DSM and Orthomosaic without artifacts.

See Figure 2. below.

 
Warning:
  • When processing step 3. DSM, Orthomosaic and Index, was already processed previsouly, the outputs will be overwritten. In order to keep the original outputs, before processing, move the outputs to another folder. 
  • When processing step 3. DSM, Orthomosaic and Index, the orthomosaic may present distortions on areas covered by points where the altitude has been modified when creating surfaces.

 Figure 1.
 
 rayCloud_before_surfaces_2.png rayCloud_after_roof.png
 rayCloud before Surface created 
  rayCloud after Surface created 
   
DSM_before_surfaces.png DSM_after_roof.png
DSM before Surface created in the rayCloud. DSM after Surface created in the rayCloud.
 Mosaic_before_surfaces.png  Mosaic_after_roof.png
Orthomosaic before Surface created in the rayCloud. Orthomosaic after Surface created in the rayCloud.

 


 Figure 2.
 
 rayCloud_before_surfaces_2.png rayCloud_after_roof_floor.png
rayCloud before Surfaces created   rayCloud after Surfaces created
   
DSM_before_surfaces.png DSM_after_roof_floor.png
DSM before Surface created in the rayCloud. DSM after Surface created in the rayCloud.
 Mosaic_before_surfaces.png  Mosaic_after_roof_floor.png
Orthomosaic before Surface created in the rayCloud. Orthomosaic after Surface created in the rayCloud.
Was this article helpful?
2 out of 2 found this helpful