RTK-georeferenced textured mesh with Meshroom (Drone imagery)

[webmap-PS]

Hello, I'm quiet new to Meshroom and photogrammetry topics. I want to compute a georeferenced textured mesh of a survey site with Meshroom. I have some sample drone images with RTK files (rinex.obs and timestamp.mrk) [withoud GCPs] to create a suitable workflow pipeline. So far I found no way to include the RTK-data in the pipeline. Are the rtk-corrected geotags already saved in the jpg or how do I get the thing running? When I let it compute withoud specifying the rtk-data the model turns out well. The problem is how to get it georeferenced? When I convert the obj-file into a las-file with CloudCompare and load it into QGIS no CRS is shown. Is there any tweak I oversaw?

I saw a option with the SfMTransform-Node but putting in the RTK-data by markers seems not the be the soluton. Didn't found a option to import the RTK-files only by manually setting the markers.

Working on Desktop PC with the recent Meshroom release.

Appreciate some help! Thanks!

[MrClock8163]

If you don't have GCP markers in the images with RTK coordinates that you measured, as I see it, the only way to georeference your model is by having RTK positions in the metadata of the images.

[MrClock8163]

Judging from the rinex.obs file name, I'd assume that's a RINEX format RTK observations file. As far as I remember, RINEX files usually store a stream of GNSS observations, which you can then process in specialized applications used for adjusting GNSS networks, and data. I reckon you would also need the corresponding RINEX capture from the base station you were using for the RTK at the time of the survey. I feel like this kind of computation is out of the scope of a photogrammetry software like Meshroom.

[webmap-PS]

Thank you! I have a sample set of drone-imagery where the RTK-Koordinates are stored in the EXIF of the Images. But when I load and process them in Meshroom, export the model via CloudCompare as .las file and load it in QGIS, the data is withoud a CRS and somewhere in limbo. I know the EPSG-Code but applying it to the las. file doesnt change it. When I perform the same with WebODM, the data is perfectly georeferenced. Do you or anybody have an Idea which step im missing? Best regards

[MrClock8163]

I feel like we need to clear up the CRS part. The EPSG code is only a metadata about the coordinates. By "without CRS", do you mean that the point cloud is not properly georeferenced, or just simply doesn't have the EPSG number embedded into the LAS? If the data is not georeferenced, you're missing the SfmTransform node in your pipeline. You need to insert the node between the StructureFromMotion and PrepareDenseScene, and set the Transformation Method to from_gps.

[!WARNING] The transformation only works properly if the position data in the EXIF are WGS84 geographic coordinates. Make sure the RTK positions you got in your images are actually WGS84 geographic values (EPSG:4326), and not WGS84 carthesian (EPSG:4978) or some other already transformed local coordinate system!

WebODM is by-design meant for larger scale surveys, while Meshroom is more on the smaller scale object reconstruction side. Because of this, Meshroom doesn't seem to bother with the concept of a CRS. It only deals with carthesian coordinates.