# Auto take off and landing at different altitudes

Imagine the following scenario:

I have to fly from a hospital and deliver medicine at a location with different altitude. The hospital is my starting point, so it will be 0 altitude. Actually, it is at 125 meter above sea level.

The target landing area is in a mountain, with approximately 600 meter above sea level, so 475 meter above my starting level.

How to plan a mission like this using a VTOL airplane. I’m using latest version of MP and arduplane with lidar to compensate for baro drift.

You try terrain follow?

Use “Verify Height” checkbox in Mission planner setting different waypoints in your mission to create a curve with main altitude changes.

Verify height means that the Mission Planner will use Google Earth topology data to adjust your desired altitude at each waypoint to reflect the height of the ground beneath. So if your waypoint is on a hill, if this option is selected the Mission Planner will increase your ALT setting by the height of the hill. This is a good way to make sure you don’t crash into mountains!

I suggest to create several waypoints because I do not think that if between two waypoints both at 0 altitude there is a hill, even with “verify height” checked, Mission Planner will avoid to crash in to the hill.

Terrain follow as suggested by cala2 should work but I never tried and if I remember well the Lidar is not working with Arduplane during terrain follow.

wrong place went to mision planer

Thanks for the suggestions. My point is this:

When I fly up, the altitude is slowly increasing to lets say 650 meter. Now I am approaching my target landing area, and I start to descend to 30 meter above my landing point altitude. At the last waypoint before my landing point, I start to transistion to hover and the lidar will be activated. (This I try already, Lidar starts at the moment I reach the last waypoint before landing).

So my altitude is 630 meter, and the Lidar will tell the autopilot I am at 30 meter. What will happen, will he try to go to 660 meter? I set my landing altitude to 600 meter, baro tell the autopilot I am at 630 meter, Lidar tell him I am at 30 meter…

I try to simulate this scenario, but I get bad AHRS in the simulator. Almost like real life … Bad AHRS …

The Lidar will tell to the Autopilot that the distance from ground will be 30 meters while the Plane altitude will be referred to Home altitude where you get a valid Gps signal .
Il you check “verify height” for your mission the altitude of the last waypoint will be adjusted based on Google Earth topology, so your plane will be at an altitude 630 meters compared to home altitude but 30 meters from ground.
That is how in my understanding things should happens.

In copters you can fly enterely whit lidar, plane only uses lidar for landing process but vtol? looks a good question, supose to land with lidar too but better if developers or someone that test it confirm it.

I figured out how to use the simulator, but still I am very puzzled. It does require that you define each waypoint with a default altitude, using verify height in your mission planning. Having done that, I chose a small hill, about 600 meters high and planned a mission.

The result was that the aircraft kept on descending to 520 meters, which was about 150 meters below the Google earth altitude of the landing spot, and then reported a crash.

Activating lidar in the simulator didn’t make any difference at all.

I agree with you, either a developer or someone who tried, should shed some light on this issue.

I think there are 4 methods of programming this…
1.) Use the verify height check box as stated above - this will use the terrain only for the waypoints, and will fly straight lines in-between the waypoints.
2.) Use absolute (drop down box) when programming waypoints - will give you straight flight lines as well.
3.) Use relative (drop down box) if you know the difference in elevations and want to use your takeoff location as the datum plane. Also flies straight lines.
4.) Use terrain (drop down box) when programming waypoints. The waypoints will be adjusted to the proper altitudes AND the path between waypoints will follow the terrain without enabling terrain following in the parameters.

When it comes to landing, I would recommend using method 4, but I don’t know how how the LiDAR will need to be programmed. I can’t find any documentation on how it is used for auto landing when in a copter mode. I’m sorry this doesn’t really answer your question though.

Would be good to have lidar for entire flight !

Search help something: LIDAR on Quadplane