Distortions and Artifacts in the Orthomosaic - PIX4Dmapper



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.


Orthomosaic before editing Orthomosaic after editing using the Mosaic Editor
Orthomosaic before editing Orthomosaic after editing using the Mosaic Editor


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  • Hu Yuan

    pix4d is famous in the world ,should be begineer user easy to operation,but,i am a user,any setup correct or wrong ,i dont know how,HELP funtion too weak,when i  finishing project, i found progress not complete ,why,i rent your monthly for year,so expensive,

    your toturial teching video,only english,i am chinese who know english ,when setup project you must let user result .but your HELP like damage machine ,.

    i very angry ,pix4d  diffcult to use,i sugesting your company ,user always stupied ,anyway easy use,chip rental ,my problem also is all user problem.

    i am a programer ,pix4d,not good software.i belive.in future you may loss your customer soon, .

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  • Holden (Pix4D)

    Hi Hung. Thanks for reaching out. If you are having issues with a project I would suggest opening a support request at support.pix4d.com. If you choose to open a support request please include a log file, quality report, and a description of the problem. 

    We are working to expand our supported languages so your feedback is helpful. Thank you.  

  • zhang haibo






  • Eugenia Pylypchuk

    Hi pix4d team,
    I got to much artefacts on my resulting ortho, such as you described in this article, on buildings, bridges and other high objects. And it takes a lot of time to correct them all mannually using Mosaic editor. Wouldn't it be easier to be able to make orthomosaic using DTM, not DSM to avoid such artefacts creation? As far as I understood there is no such option.
    And do these artefacts apear just due to difference in height between ground and building roof or the top of other vertical object, or maybe due to some other reasons (noise, errors etc.)?
    Maybe you'll suggest something to reduse amount of such artefacts?

    Thanks in advance.

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    Aaron (Pix4D)

    Hi Eugenia, Thanks for your interest in Pix4D

    Using the DSM as the basis for the Orthomosaic is really the preferred way, you could edit the point cloud such that all data that was not Ground or Road Surface was moved to the disabled group, then the DSM would really only reflect those pixels normally shown in the DTM (Ground and Road Surface), however, I don't believe the resulting Orthomosaic would look very good as the Buidling, Human made objects and High veg would not have any supporting 3D data for them.  I would suggest increasing the overlap among your images to help reduce artifacts and you could increase the Minimum number of matches as well.  I hope these suggestions help, lets us know if you have questions regarding a specific project.


    Aaron Woods

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