Continent terrain tiles failing prearm checks

[Georacer]

Bug Report

Posting this for recordskeeping.

The SRTM3 continent files seem to fail our prearm check for the tile version.

Issue details

Run a simulation with

sim_vehicle.py -v ArduPlane -f quadplane --console --map --custom-location=47.38719,18.9577,99,0

Set TERRAIN_OPTIONS=1, TERRAIN_FOLLOW=1536.

Delete any downloaded terrain files in the terrain directory.

Paste from the Eurasia dataset the following:

├── N46E047.DAT
├── N46E048.DAT
├── N46E049.DAT
├── N47E017.DAT
├── N47E018.DAT
├── N47E019.DAT
├── N48E047.DAT
├── N48E048.DAT
└── N48E049.DAT

Then reboot.

This yields a preflight failure:

Version
4.7.0-beta3 and -beta5

Platform
[ ] All
[ ] AntennaTracker
[ ] Copter
[X] Plane
[ ] Rover
[ ] Submarine

Airframe type
N/A

Hardware type
SITL

Logs
Reproducible in SITL, but available upon request.

[rmackay9]

We discussed this on the dev call and we think that the linked PR from @arynrosh is likely correct (thanks!)