Hi,

I want to plan a mission where Home is, let's say 1,000ft. The WP is 1,400ft but there is a small mountain between the WP1 which is 2,000ft. What is the most efficient way to plan such a round trip? Obviously, I could use +2 intermediate WPs at 2,000ft, one outbound and one inbound but I would rather use just one WP and Home. If I check Verify Height will that do the trick? Also, if Verify Height is checked, will the entire flight be terrain following?

Thanks for any help from you experts,

Steven

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Can anyone help me with this, please? The DEVELOPERS certainly have to know the answer.
Thanks,
Steven

First off - I fly in Oklahoma where the ground is flat and so I haven't USED verify height.  But according to the manual, it doesn't exactly do what you want, because it only checks and adjusts the ground altitude at waypoints.

By default, the mission planner uses 'above launch site' as the reference for all altitudes, and with 'verify height' turned on it uses 'above current ground level'.

so with verify height turned on, you could set

WP1 at altitude 100' a little bit upwind of the takeoff site

WP2 at altitude 100' on top of the mountain

WP3 at altitude 100' at the target site

WP4 at altitude 100' on top of the mountain

WP5 at altitude 100' a little bit downwind of the takeoff site.

or with verify height turned off you would set

WP1 at 100'  (above launch site)

WP2 at 1100' (above launch site)

WP3 at 500' (above launch site)

WP4 at 1100' (above launch site)

WP5 at 100' (above launch site)

or with absolute altitude turned on it would be

WP1 at 1100'

WP2 at 2100'

WP3 at 1500'

WP4 at 2100'

WP5 at 1100'

All of these three courses are exactly the same - they're just different ways of entering the values.  If you do this, the aircraft will take off at 1000' ASL, fly to 1100'ASL, ascend to 2100' ASL to cross the mountain with 100' of clearance, descent to 1500' at the target location, climb back to 2100' to get back over the mountain and then return to 1500' and lined up for a landing.

If you just set WP 1 and 3 and 5 from the above example, even with verify height turned on, you're going to crash into the mountain.  The MP only checks and adjusts for terrain height at waypoints.  To my knowledge there's no way around this right now.  Maybe in the future the Sonar sensor or a machine vision system could let you actually see the terrain, but right now we just have to plan ahead for it ourselves.  There's not enough memory in Ardupilot to store the terrain height values for every place we could possibly fly it, and the programming doesn't RELY on the base station for anything when on an Automatic path - all of the decisions are made in the air so if telemetry is lost, the vehicle tries to complete the mission.

Is there a reason you don't want to give it a couple of extra clicks to make sure you get over the mountain?   I'd personally set my 2100' ASL waypoint in FRONT of the mountain and another 2100' WP substantially BEHIND it to make sure I'm up high way before I need to be and back down after all risk of collision is passed.  And for that matter, I'd want more than 100' of spare clearance going over a mountain, but I'm just using that number for easily following the discussion!

Great reply and correct,

the verify function oly checks the WP and the track on the ground can be off as it only takes google earth points every 100foot along the route. plenty of distance for the odd 300 foot vertical cliff wall to apear out of nowhere. why not go to the other side of the mountain and keep the UAV in LOS. I decided a looong time ago that RC aircraft and mountains dont play together well !!

Thank you for answers. That clears it up for me. I can use multiple Way Points, I was just curious how sophisticated MP and AP were.
Thanks again,
Steven

Hello Art, this is an old threat, however please could you tell me how to switch between Relative and Absolute altittude, I don´t see any option in the screen.

thanks

I can help you with this one. Go to the MP Flight Plan tab. Under Way Points, you will see a drop down box for absolute, relative and terrain.

Steven

Go to MP, then to Flight Plan tab. Under WP, there is a drop down with absolute, relative and terrain.

Verify height works as above. You are asking if arduplane supports terrain following in auto mode. Yes, it does. It is a parameter you change to on. But beware, sometimes it doesn't work perfect and your plane can only fly up so fast, so have it look ahead adequately.

Just had an experience (crash) that bears on this discussion.  It was an Auto Mode mission starting from my backyard, going up to 40m to avoid some low hills, flying out to a lake which is about 65m lower than my yard, dropping to 15m for a Loiter cirlce to shoot some video, then rising back to 40m, and home.  It never made it home, and I found it had crashed into one of the low hills on its way back.  I was able to retrieve it and get the log (here attached).  I have a lidar unit installed in the belly that gives distance about ground readings up to 20m.  Arducopter 5.5

Per the log of BARO Altitude, (and pic attached) it behaved as expected until it got to the lake.  It then descended to 40m below starting elevation (a descent of 80m which would put it about 15m above the lake), did it's circles to shoot video.  Then unfortunately, it came up only 40m and headed home.  Not high enough to avoid the low hills.  

My questions are: How did it go down to 15m above the lake since per the log the lidar RNFD Dist seems valid only at the very beginning and end of the flight? Why did it seem to reset the base elevation and not come back up to 40m above home?  How should I have set up the waypoint altitudes?  Any ideas? 

Attachments:

I believe I've answered my own question.  I recreated the symptoms, where it fails to come back up to the correct altitude after going down to a lower altitude.  I had the parameter WPNAV_RFND_USE set to 1 (enabled).  Changed it to 0 and all is well, it goes up and down per waypoint altitudes. 

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