hello,friends!
I test terrain following last week,but failed badly,almost lost my plane!There were some problem puzzling me.
First,what's the difference between Absolute and Terrain?I have read "http://plane.ardupilot.com/wiki/common-terrain-following/",it says as bellow But it didn't mention what should be done in the MP? Does all I need in the MP is just to choose "Terrain"?
Second, should I both choose the "Terrain" and "Verify Height"? I see that once I choose "Verify Height",the "Alt" will change.but i can't figure out the relationship.
Last, sometimes "no terrain data"will show in the MP if I connect PIX.I think it's beceuse I set "TERRAIN_ENABLE to 1 and TERRAIN_FOLLOW to 1",and no terrain data in SD card. Does that mean that if no prompt shows,terrain follow is ok?
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It is a pity that there is no wiki where a detailed description can be found or test flight can be reported & shared. (I do have my own wiki where I`m collecting all type of DIY Drones data and info, but I do not think that is the best place for the moment to create a detailed description - you might visit it at drones4all.info)
By the way, I created another discussion issue at http://diydrones.com/forum/topics/terrain-following-documentation-q... where there are some other doubts I have in relation to TERRAIN FOLLOWING.
Hi did you ever get this sorted out? I wish there was a detailed glossary on the parameter terms. For example, the difference between ter_alt and curter_alt?
Anyway, if you figured it all out, I would appreciate a few details on your approach. Thanks!
Terrain will try to maintain a constant height above the ground underneath it using an uploaded terrain database. This calculation occurs real time inside the Puxhawk, even if not on a flight plan, like RTL.
Verify Height is similar, but the calculation occurs inside Mission Planner only at each waypoint. It simply adds the Google Earth elevation to the requested altitude. If there is a hill between waypoints, it will not know to compensate, whereas TF will adjust. Verify Height is also available to the APM because no onboard data storage is required.
Much of the difficulty and confusion you are experiencing is because the TF feature is not fully implemented in MP. It was developed by Andrew Tridgell who uses MAVProxy instead of Mission Planner.
There are many github requests for terrain following improvements in Mission Planner but they are coming rather slowly. You may notice a new small improvement where the Elevation Profile tool now shows the aircraft following the terrain. There is still a lot of improvement needed to visualize the aircraft's vertical path.
Here are some discussions:
https://github.com/diydrones/MissionPlanner/issues/566
https://github.com/diydrones/MissionPlanner/issues/573
hi,iskess,
Thanks for your reply.And I have read your post,many problem you mentioned is my question.
Have you ever successfully test TF function?And can you post the TF setting? I badly need this fuction because my area is extremely hilly!
Thanks!
I want to fly in mountainous terrain.. What's your setting? Just set "TERRAIN_ENABLE to 1 and TERRAIN_FOLLOW to 1; and select terrain while mission planing,not select verify height and make sure terrain data available in SD card? Another question,my
What does look ahead para mean.?
For example,if i set look ahead=500 m, fly height=200m, and if the Home alt=100 ,highest point's alt in the 500m distance ahead is 400m. What would happen ?
At the launch point,will it fly at 600m(200m higher than the highest point)?
Or just fly at 400m high to make sure the plane won't crash into the highest point?
So the higher the Look Ahead, the smoother the vertical profile will be. If you are just interested in a safe ground clearance then use a big Look Ahead value. If you want to follow the ground contours very closely, then use a smaller value. There is no way to know for sure if the terrain gradient will exceed the aircraft climb performance. The Mission Planner Elevation Profile is the only way to visualize this.
Hi @iskess , could you tell me where I can find the Mission Planner Elevation Profile screen?