Calculate Coverage Area of Chunk

[ma5973]

Hello everyone,
I would like to calculate the coverage area of a chunk, as in the report, in order to export the metadata of my projects to a JSON file.
I thought the “coverageArea()” methods of the "Metashape.Orthomosaic" and “Metashape.Elevation” classes would do exactly that, but when I use this method for a project, I get 1,338.34 m² for the DEM and 17,855,510.78 m² for the orthomosaic, even though I would expect the values to differ only slightly. Visually, the DEM should actually be larger than the orthomosaic.
The report shows 13.8 m² under Survey Data, which differs from both values.
The workaround with the seamline calculation, which is mentioned here (https://www.agisoft.com/forum/index.php?topic=15266.0), also yields different results and is not practical for large projects.

Am I overlooking something? Is there another way to obtain the “Survey Data,” in particular the coverage area, from the report?

Thank you in advance.

[Alexey Pasumansky]

Hello ma5973,

Do you have chunk, DEM, shapes and orthomosaic all referenced in the same coordinate system?

[ma5973]

Hi Alexey,

Yes - chunk, DEM and orthomosaic are in ETRS89 UTM32 (EPSG: 25832). Calculating the seamlines takes too long for such large projects, so I don't have any shapes.

Further info: I'm using Agisoft 2.2.0.

Thanks for your help.

[Alexey Pasumansky]

Hello ma5973,

Can you please try to check all three values in Metashape Pro 2.2.2 version? If there is still considerable difference, can you please share the screenshots of DEM and orthomosaic from Ortho view mode (saved without any changes to zoom) and also Survey statistics page from the Report page?

I have cropped DEM and orthomosaic using the same boundary shape and after that all three values appear to correspond each other.

The value on Survey Data page corresponds to the DEM area that is seen by at least one aligned camera.

[ma5973]

Hi,

here are the screenshots of the DEM, the orthomosaic and the survey data in the report.
You can also see the reference system of the DEM and Orthomosaic and the results in the console.

How do you calculate the area in the survey data? Do you use the generate seamlines, to see which part is seen by at least one aligned camera?

Thanks!

[Alexey Pasumansky]

Hello Hello ma5973,

Thank you for sharing the screenshots.

Seem that values for orthomosaic.coverageArea and Coverage Area from report are correct. The latter value (from report) considers the boundary shapes and discards the area outside the boundaries  - you can see that there are straight cut edges on Survey Data page.

But the value for the elevation.coverageArea is strange. Can you try to duplicate DEM with clip to boundary shapes option enabled and then check the area value using Python command for the duplicated DEM?