DTM/DEM issues for multiday flights

When capturing multi-day flight data we see elevation issues. For example, a flight occurs in three ‘strips’ over three days. Each day we take off from a new point. Typically, each day has a new starting elevation. Whether we upload and process this data as one day or multi-days, we end up with ‘banding’ artifacts in our elevation maps. The banding illustrates the difference in take-off elevations between the days. This essentially makes our elevation exports useless. Any ideas? The hardware is a P4 with RTK. DD staff haven’t been able to provide a solution.

The second image is a zoom of the artifact in the center-right of the first image. There is a true 1m elevation gradient over about 30m here, not a sudden 2m change. Images were processed as a single day.

The same issue is the third image, however, processed as separate days at a different site.

Welcome Enaz! How are you acquiring your base points? Do you have checkpoints common to all sections? This will happen but should be within the tolerance of the GNSS hardware. Have you PPK’d the logs? You might have had a false fix somewhere along the way. I hate seeing a 6ft bust because that’s awfully close to a rod height…

My colleague does the flying and I’m do the mapping/analysis. He’s just taken off to another country for the month, so I’m outta my depth!

I’ve got access to all the files the drone exports (1.2tb for this project!), as well as the drone deploy projects and files. Is there any way I can use this to find the information you are after?

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As a bandaid for now, you could use the Calibrate Altitude tool in DD to offset the maps so they match at their boundaries. This will make your complete map look 10x better.


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Cheers. Unfortunately, it doesn’t matter what they look like as it is the underlying elevation data of which I need to be correct. When I export the DTM it includes these artifacts which are then introduced into subsequent analyses

I think that is what @SolarBarn is trying to reference but did you process all day’s images onto one map? His suggestion would work if they are individual maps and you are combining data after export. This would be a better way of processing multi-day missions. Similar to lidar when you have to rectify the bands.

If you can find two photos, one from each day that are next to each other look at the exif data and see if the altitudes match.

I don’t recall, does the P4 RTK use terrain following?