this fixes height_above_terrain() to give a correct value when HOME is
not on the ground after the user has done a DO_SET_HOME with a
home position that is not at ground level
The squares surrounding the current location were only checked when we went to send a terrain request. This means it was possible that:
- the number of pending requests could go to zero
- prearm checks would pass
- vehicle arm is attempted by the user (or a script, or ....)
- the code would call AP_Terrain::send_requests which would create more pending requests
- the arming sequence would fail
It's also possible for the arming to succeed, and then we're flying in violation of the intended prearm checks.
Doing things in the update function has the additional advantage of making things more efficient as we can push out terrain requests more often.
looking at pending is insufficient as we may have more mission items to check to see if they need other pieces of terrain. That is, terr_pending can go to zero momentarily and then go back to a non-zero number as Terrain's update method checks the mission and rally libraries for more terrain requirements.
Without this patch the prearm checks can momentarily pass, allowing the vehicle to arm. The vehicle could hit a terrain failsafe later if it doesn't manage to get the data while in flight.
this restores the terrain adjustment functionality removed in #19946,
but without the problematic approach of always using home (which can
be moved in flight) and with a TERR_OFS_MAX parameter to limit the
amount of adjustment
this sets the acceptance margin for GCS generated terrain data. You
can raise this to allow old data generated with the less accurate
longitude scaling to be used
this fixes a problem where two different locations could both be
mapped to the same disk block in the terrain/*.DAT files. That meant
that pre-filled terrain on the microSD card would sometimes require a
download in flight. It also means that a RTL with loss of GCS could
sometimes fly through a region with no terrain data available
Other changes in this patch:
- allow for a 2cm discrepancy in the lat/lon of the grid
corners. This is needed to allow for slightly different floating
point rounding in tools that pre-generate terrain data to load on
the microSD
- added TERRAIN_OPTIONS parameter to allow the user to disable
attempts to download new terrain data. This is mostly useful for
testing to validate a terrain generator
instead of computing the terrain status on-demand, assign it in update() and cache the result. Then external tasks that check the status won't be doing terrain intensive calculations in their thread. All the calculations needed for the status were being performed in update already so this is an optimization.
Andrew Tridgell
Randy Mackay
Peter Barker
Henry Wurzburg
Jaaaky
Michael du Breuil
Pierre Kancir
Tom Pittenger
Dr.-Ing. Amilcar Do Carmo Lucas
Mathieu OTHACEHE
Luis Vale Gonçalves
Caio Marcelo de Oliveira Filho