Blatent inaccuracy of elevation map


#1

I am a new user of DD and wanted to use it for determining where to put drain channels in a paddock. I am not using GCP’s and a few inches here or there are not important.

I ran a small mission of some of the paddock and that seemed to work out well

I then tried the whole area of the paddock that I want to work with and it didn’t come out so well

Not only are the arrows obviously pointing uphill when you stand in the paddock, but every winter lakes of water are at the blunt end of the arrows and don’t spill out in the direction of the arrows as the elevation map shows they should :confused:

The missing section from the main map was probably caused by photos failing to upload (using satellite connection with high latency seems to slow uploads tremendously - but that’s another story). I uploaded the missing photos seperately and put them into a new image which did seem to work well and contradicts the “main” map

Thoughts on what went wrong?

Bruce

Edit: On the last map point A is lower than point B, but I suspect that this might be caused by being on the edge of the photos


#2

Sorry to see this. Relatively flat areas can have a bowing effect - better triangulated data in the interior with multiple rows of images verses one row on the ends with little to no triangulation. Taking some inward looking overlapping oblique photos can help rectify this. The information put into the map must be managed to optimize the outcome based on the particular subject matter. Some of this comes with experience. It is also good to set your flight parameters about 10% beyond your desired area to get good overlapping data throughout.


#3

I appreciate our point about flying beyond just the area to be mapped. In this case there was a number of photos that should have provided triangulation

If I go back and take some inward facing oblique pictures, should these be from the same height as the original flights, or is the height of the drone not that critical?

Something that i hadn’t appreciated when doing the flights is that they should be all taken off from the same height, so I might need to redo them anyway.

I’m not looking forward to having to try to upload so much data again. Do you think it would make any difference to the finished product to use turbo upload?

Bruce


#4

Hello @SouthCoast

Turbo upload produces fairly great results. If you want the maximum quality of your map, I would upload all images while you have a good internet connection. I would fly with higher overlap (80/80 value) and also to fly at the same altitude as your obliques.

Thanks.


#5

Ok. Thanks. I’ll give that a try today. The uploads seem to be very slow over satellite - I can get only about 0.5Mb/s (60-70KB/s) even though my connection supports 5Mb/s and I regularly upload other things at close to that. I suspect the problem has to do with latency

Bruce