Does someone know and can share what the difference is between the Altitude settings in Mission Planner for Relative, Absolute and Terrain. I know that the Terrain is for those planes equipped for terrain following, but what about the other 2 settings? I have had some problems with my X-8 wing holding requested altitude and suspect this might be the problem. HELP and thanks!
You need to be a member of diydrones to add comments!
Replies
I think you mean to say "relative, MSL, and AGL".
I agree that "absolute altitude" is wrong, and has the potential to confuse someone with aviation knowledge.
I think many would like to be able to use AGL. I think part of the problem is that sensors and data storage and computing headroom on most FCers don't make true AGL possible at this time. It takes a lot of data room to pre-store much terrain or sensors that most multirotors don't have at this time.
It is much simpler for the FC by barometer to have a baseline form where it armed and then do it's best to provide a "relative altitude" from that start point. Simple to execute and simple to understand even though it is not always the most useful.
It's interesting that there is a "Absolute Altitude" vice "Means Sea Level or MSL" and a "Relative Altitude" vice "Above Ground Level od AGL". Shouldn't everything be referenced in mission planning as it is in the aviation community as a whole?
In addition to this, I think a sonar, lidar, or something equivalent is used to terrain following directly below the aircraft. The idea of have it in the flight computer would be nice but I do not think current designs have the robustness to be able to hold all the DTED (Digital Terrain Elevation Data) it would take to be able for the air vehicle to fly truly autonomously. Therefore, it makes sense to use waypoints AGL and fly in Auto if you plan to fly along diverse terrains.
Terrain Following came out in 3.1 and uses the CF card to store the terrain data.
http://diydrones.com/profiles/blogs/terrain-following-added-to-apm-...
The reason we don't use the term AGL is because it is not accurate. We use "Relative" because it is relative to launch elevation, not all the ground.
I agree that MSL would be a more aviation friendly term than Absolute, which is more of a cartography term.
Note that according to this: http://copter.ardupilot.com/wiki/common-terrain-following/
terrain following applies only to arduplane, not copters yet. So don’t count on this feature for automatically adjusting your altitude if you fly a copter.
I think maybe there is some confusion about what was discussed above. It was not "Terrain following" but rather the "verify height" check box on the waypoint menu of mission planner.
"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!"
From: http://copter.ardupilot.com/wiki/common-planning-a-mission-with-way...
I know that in Mission Planner there is a verify height check box. If it is checked it will adjust the way points so that the height of the mission will match the height of the ground at that location. So if your default height is 20 Meters and the ground is 10 Meters above Home then it will make a way point height of 30 Meters.
This is based on Google map data and where you have home defined at the time. Otherwise all heights are relative to where you take off from.
Do 'Terrain' waypoints do the same as the 'verify height' checkbox, if not what's the difference?
-
1
-
2
-
3
of 3 Next