Re-flying a tricky site - first attempt mostly failed

Hi everyone, I have a few questions about this one area to map… again. Long story short I arrived on site and had a multitude of problems, all unrelated to each other:

DD did not recognise that my Inspire 1’s camera was actually working once in the air and would go through the pre-flight checks and mark the X5R camera as working, only to get to the starting point and turn around and fly home with “camera calibration” error. It has never done this before on any mapping mission. Very embarrasing. After wasting 5 batteries trying to sort it out, from checking all of the settings in DJI Go, then going back to DD - the problem persisted. So I flew it manually through DJI GO. The camera worked just fine and I managed to get a decent set of photos. Then my brand new auxillary car battery that I use to charge everything and run my laptop decided to drop a cell.

As automated flight through DD was out of the question I decided to go with my new (4 day old) DJI M2EA. DD cannot be installed on the smart controller so I ended up automating the flights with DJI Pilot which gave me problems by refusing to fly because of “restrictions” which were unspecified. So I manually flew the next section of the site. The third section was finally flown with DJI Pilot. This messing around with problems previously non-existent caused the 3 hour job taking 2 days. Luckily it was helping out a friend instead of a paying customer.

Now, because of 22GB of data and only having access to mobile data for uploading I had to drive 4.5hrs home to upload. And it seems to have been a waste of time.

Referring to the picture, the northernmost part of the site (on the right) is for some reason showing up as being a great deal higher than the middle section, even though it is lower - so my DTMs and model is no good. There is decent overlap in the dataset between these two sections which were taken on the same day, just as there is between the mid and left sides which turned out perfectly fine despite these two being flown on different days, both manually with different drones and cameras. These two sections that stitched well had only one thing in common and that was the takeoff location which was at the highest point roughly in the middle of the image. So it seems I need to re-fly.

So to give you an idea of the size and lay of the site it is about 32 hectares and has a height difference of 75m (248ft) from the lowest measured point (ignoring the right side of the image which is likely 15ft lower)) to the top of the tallest tree.

I’ll need to meet the following goals:

  1. Get the best GSD on the lowest points as possible for weed and seedling counts
  2. Get good stitching on the tree tops around the edges of the property which are 40m tall in many cases as they are part of the survey too for species/density/weed trees
  3. Have a continuous DTM come out of it for contouring.

So, considering the two datasets on the same day from the M2EA stitched far worse than the two from the Inspire/M2EA on different days at different times (which worked well) how should I re-fly this?

Thanks for your help as I have never had any of these issues come up before.