Distortions and Artifacts in the Orthomosaic - PIX4Dmapper

Cause

The orthomosaic is generated based on the DSM 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: Photo stitching vs orthomosaic generation.

When computing the Densified Point Cloud, the altitude of the points will not be perfectly estimated. There are always some errors and noise that are minimized for good datasets (high overlap, the good visual content of the images, use of GCPs, etc.).

These errors and noise result in altitude differences for points that are supposed to be at the same altitude, such as points that belong to the same roof edge of a building or the same edge of a bridge. This altitude difference explains the distortions that appear in the orthomosaic on building edges, bridges, etc.

Note: The orthomosaic receives as input the DSM, and the DSM receives as input the point cloud. If the point cloud is noisy, the DSM may also be noisy. Make sure that the results of step 1 and the point cloud are optimal before generating the DSM and orthomosaic.

Solutions

Improving building artifacts: How to correct Building Artifacts in the DSM and Orthomosaic.

Orthomosaic before editing

Orthomosaic after editing using the Mosaic Editor

Improving the aspect of bridges: How to improve the Visual Aspect of Bridges in the Orthomosaic with the Mosaic Editor.

Orthomosaic before editing

Orthomosaic after editing using the Mosaic Editor