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PV2+ Ground Station Way point Altitute Setting
1649 13 2014-10-21
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aerialpicturean
lvl.2
Flight distance : 1322064 ft
South Africa
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Hi there

I live on a hill and am planning a Ground Station waypoint flight but have some obstructions to clear which is a bit farther down the hill.

Is the height I set at each way point down the hill calculated from Take-off (Home point) position or from natural ground level?

What happens if I set the Home point in the air? Is the height setting at each waypoint calculated from the Home point in the air or natural ground level?

Thanks


2014-10-21
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jmtw000
lvl.4

United States
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I believe the altitude is from the ground even if you set the home point in the air. Also, be aware that the altitude is far from exact. So make sure you leave enough distance from obstacles to compensate.
2014-10-22
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T J Gilbert
Second Officer
Flight distance : 74659 ft
United States
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Waypoint altitude is referenced off of Home Point altitude.
If you land at a point lower than Home Point, the craft just keeps descending until its sensors detect no downward movement.
And, like jmtw000 said, don't count on exact altitude accuracy.
2014-10-22
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aerialpicturean
lvl.2
Flight distance : 1322064 ft
South Africa
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Thanks for the feedback. I will leave a large margin for error!
2014-10-23
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T J Gilbert
Second Officer
Flight distance : 74659 ft
United States
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aerialpicturean Posted at 2014-10-24 02:25
Thanks for the feedback. I will leave a large margin for error!

If you're like me, I'm terrible at judging a tree's height in feet or meters.
So, if I think 60m is enough, I enter 100m...
2014-10-23
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aerialpicturean
lvl.2
Flight distance : 1322064 ft
South Africa
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Yes, I think the tree is about 60m in height, but the ground level at the tree is about 20m lower than my take-off point.

So I will set a way point above the tree at about .........100m??
2014-10-23
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T J Gilbert
Second Officer
Flight distance : 74659 ft
United States
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aerialpicturean Posted at 2014-10-24 02:37
Yes, I think the tree is about 60m in height, but the ground level at the tree is about 20m lower th ...

Set your waypoint altitudes w.r.t. Home Point altitude.
60m - 20m = 40m
100m should clear the tree by 60m
You can try that knowing it's generous, and then set it lower on the next mission if you want to get closer to the treetop...

2014-10-23
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aerialpicturean
lvl.2
Flight distance : 1322064 ft
South Africa
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That correct, but don't want to take changes the first time around. Especially when I loose GPS contact and the return home feature kicks in.
2014-10-23
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jmtw000
lvl.4

United States
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T J Gilbert Posted at 2014-10-22 23:19
Waypoint altitude is referenced off of Home Point altitude.
If you land at a point lower than Home P ...

Is it really referenced from the home point and not the ground? I've set the home point about 100'  in the air before and programmed a ground station mission with waypoints set at 200'. The altimeter on the Phantom read 200' at those waypoints, not 300' as would be expected if it were from the home point. Is the altimeter set to 0 at the home point? I will test this more thoroughly this week and report back.
2014-10-24
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aerialpicturean
lvl.2
Flight distance : 1322064 ft
South Africa
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Thanks, will be great to see the results.

Just realized that I wrote some real rubbish in my previous post.

"How can it return home if you loose GPS signals???  "

2014-10-24
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T J Gilbert
Second Officer
Flight distance : 74659 ft
United States
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jmtw000@gmail.c Posted at 2014-10-24 20:58
Is it really referenced from the home point and not the ground? I've set the home point about 100' ...

You are seeing what I'm talking about.
Home Point altitude (the reference for waypoint altitudes) will be considered to be zero.
Most of what the FC uses as an "altimeter" is barometric pressure.
Some think there's a little bit of GPS altitude triangulation happening, but no one truly knows.
Therefore, the FC has no way to know it's initial height ASL...
2014-10-24
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DJI -Lisa.zhu
Second Officer

China
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The home point is caculated from the the natural ground level.
2014-10-26
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jmtw000
lvl.4

United States
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I did some testing today and can confirm that the altitude of the waypoints in the Ground Station app are definitely relative to the ground and not the home point if it's set in the air. I manually set the home point while the Phantom was about 40' from the ground. Then I landed and created 3 waypoints in Ground Station. The first was at 50', the second at 100', and the third at 20'.  I then sent the Phantom on it's mission. I could see that at the first waypoint it was slightly higher than where I set the home point and at the second about twice as high. The third really proved it though as I could clearly see the Phantom was only 20' above the ground and well below where the home point was set.
2014-10-28
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aerialpicturean
lvl.2
Flight distance : 1322064 ft
South Africa
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Good to know. Thanks for the results
2014-10-28
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