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Different geolocation orthomosaic and pointcloud

Hi,

If I make an annotation in the 3D view , the polygon should be the same in the 2D view ?

But I have a difference:

In a third party software the pointclouds and the orthomosaic have the same position when I import them…

What should be the problem ?

thanks a lot

Hi,

Yes, 2D and 3D should be synchronized.

What is the name of the project or its ID (you can read it in the URL) so that I can check if I see any issue?

Did you upload an edited point cloud? This might lead to a shift with respect to the 2D.

…/61401/dataset/738451/map

The point cloud comes from a third party software (the data comes from a leica citymapper)

In Qgis or autocad the point cloud and orthomosaic are on the same position…

Thanks for the link.

Could you try to generate another orthomosaic with the following coordinate system: http://epsg.io/31370-1609 ? This includes the TOWGS84 parameters for the most precise transformation, which is the same that Pix4Dcloud picks.


Here the instructions on how to use a prj file to define your output coordinate system.
You can then replace the orthomosaic file from the Files > Results section of your project.

Let me know how it goes

Hi @drone4,

I have some updates for you regarding my previous answer.

I actually tried to import your orthomosaic in QGIS with different transformations and changing them doesn’t seem to influence the position of the polygons. Therefore I am considering the fact that your point cloud might have a different coordinate system.

Which are the coordinate systems of the single outputs? Do they all match? Do you have the parameters defining the coordinate systems for all the outputs so that we can ensure the files have the same CS? We don’t support different coordinate systems in the same project.

It also looks like Pix4Dcloud is not able to read the coordinate system from your las file.

How could you check that point cloud and orthomosaic are aligned in QGIS?

I imported the ortho and the annotations and they match with what I see in Pix4Dcloud.

Hi Alice,

You should import the pointcloud in a CAD-software.

See printscreen of al the pointclouds from that area (februari 2020-augustus2021) and the position is 100% the same.

See attachment for a printscreen from the pointcloud and the ortho tiles =

I dubbelchecked this error with drone data that came directly out Pix4D Mapper (data from feb 2020) (…site/61412/dataset/627756/model)

Here you can see that the coördinats of the 3D are very far of the coördinates of the 2D, the coördinates of the 2D viewer are the right ones.

See below the coördinates of the 2D =

here the coördinates of the 3D =

at that time we didn’t saw the difference because the difference was exceptional high, with the latest data (from the citymapper) the error between ortho and pointcloud is smaller and we see the 2 annotations in the same viewer (in 2D we see the annotations we made in 3D, and vice versa)

So, I think that pix4d cloud doesn’t import the las file correctly because the problem occures with data from pix4d mapper and 3th party software…

kind regards,

Gregory

Hi Gregory,

The case for project 627756 is different. There you are adding the measurements on the 3D Mesh, that is not georeferenced and therefore the coordinates between mesh points and the points belonging to other outputs are different. To align the mesh with the point cloud and the other outputs, I recommend that you read the suggestions for the mesh upload at this link. The annotations already align with the 2D layers with the current outputs if you place them on the point cloud. Uploading the offset file as explained in the linked documentation article, will solve all your problems there.

The project 738451 makes me think that we do not handle las files coming from Leica Citymapper very well. I can investigate a bit more into this but I cannot guarantee that we can add support for this at the moment.