Share your volumetric measurement experiences

[MrCarbon]

I am going to do some stockpile measurements of some composted material.
what are your guys's tips for best results?
Ideal lighting... meaning very sunny day or not so sunny?
altitude?

I will be using phantom 4 and no GCP, although I dont know if GCP do any good in this application.
I will be trying drone deploy, MME, and maybe others for post processing
Thanks

 

[African Sky]

I also have questions around this point:
What is the optimal hight to fly above heaps of material in order to get the most accurate volumetric measurements?
Optimal speed, Overlap