Thanks @Christina. Much appreciated. I hope it is recognised by your team that I really am trying to make it work and not messing around. I honestly thought we had ironed out the issues and was about to place the order, but these new relatively important issues that have just come to light are show stoppers if we can’t find a workaround.
I’m looking at your image @SolarBarn Terry and wishing I had received similar results. What you have there I would be over the moon with. The contours running along the roof pitches are uniform and parallel with the ridge/gutter. Very very good.
This is my roof from another map. In trying to understand how to mitigate the ‘sagging effect’ Dave mentioned I unfortunately then learnt of the bowl effect. The contours are at 0.25m centres.
The roof is in fact double pitch, with the ridge being horizontal, not having a 2.25m fall on it.
Below is the wider site. I got hit hard, throwing the site’s elevation data out by several metres. Whereas it is possible the sagging affect found its way into this map, it going to be difficult to prove due to the extent of the ‘bowling affect’. The drone’s direction of flight was parallel with the ridges and which would have been covered in a couple of passes, just after a change in direction. The images would have been taken within a minute of each other.
The image below is at 1m contours.
With DD’s generosity, I am currently running the process again whilst including the GCP data this time. It’s lucky I put the GCP tiles down on the ground over the existing survey nails at the time the drone flew its mission. It will be interesting to compare the two results using the identical images.
I’m wondering whether to go back out to the car park site to take some oblique images, or is it too late? Do the oblique images need to be taken at the same time of day with the same atmospheric pressures and gps locks? Does the drone have to be at the identical height? Which height? The actual 22m it was set at or the 17m it possibly dropped to?
Failing that, take the GCPs and start again.
Thanks all.