Thanks Ed... I suspected as such but wanted confirmation. I'll do a short test run of a few points out and back. I thought about setting it up to follow the terrain but from that height I can't tell how tall the trees are, and there are just a few but mostly scrub. Thanks again.
Gary
I would approach it with a 'survey' flight to measure things around, using safe margins.
After watching the video, I start trimming it down, fine tuning the mission. Litchi allows you to go down too (I've reached -54 ft).
You can check the real heights as measured by Mavic/Litchi reading the Log or SRT files (good source for new waypoints coordinates too).
SRT files can be recorded to your microSD card together with the video file, you must set Video Caption ON on Litchi settings.
In case you have only one shot to make it on location, the better you prepare, the better results will be.
For such you could start with Google Maps 3D or Google Earth.
Then you can plot the waypoints using elevation data: WP Height = Elevation MINUS TakeOff_Point_Elevation PLUS Flight_Height (100 ft?), knowing there is an error margin embedded.
Prior to mission flight, you can take a short survey flight (3 minutes?) just to measure the real Litchi height perception on location.
You just need to get close to some chosen landmark and check the Mavic height.
Take the difference to the elevation data used while planing and apply to all your waypoints (batch edit).
Go for the mission and keep your finger ready to switch to Sport Mode if something looks wrong ;-)