Litchi "Above Ground" Altitude Accuracy

[caleb1]

When using the "Above Ground" option in litchi when setting altitude for a waypoint, I am wondering if anyone might know how accurate it is when using the online elevation built into litchi. I have a first waypoint set at about 400 feet above my house, then many other waypoints at various alittudes, then I get to a few waypoints over water with the altitude slider set to "16" and the above ground box ticked. Since these 16 foot waypoints are over water, I am wondering if the above ground accuracy works well over water. It probably does, but I though I'd ask here for experiences, because if this is inaccurate, it could mean the life or death of my drone, if you know what I mean. These waypoints are going to be somewhere where I cannot see with human eyes, and the signal will most likely disconnect (due to the low altitude), so I would be totally trusting Litchi. I have attached the KMZ 3D path file for this mission as well as the litchi file importable into litchi, if anyone would like to have a look. (they are in a zip file because the forum wouldn't let me upload KMZ and litchi files.)

Thanks,
Caleb

 

[sar104]

The actual ground elevations are probably accurate to within a few meters, but do not take into account the height of vegetation, and you cannot trust the aircraft relative altitude to better than a few meters either. All the altitudes that are defined relative to ground level are converted by Litchi to elevations relative to the takeoff point, since the aircraft does not have a good measure of absolute altitude at takeoff. I would be very concerned about the descent to WP 52, for example, with trees at the edge of the water.

 

[Former Member]

These waypoints are going to be somewhere where I cannot see with human eyes, and the signal will most likely disconnect (due to the low altitude), so I would be totally trusting Litchi.

If you are religious man, you might want to recite a prayer before the voyage. Kamikaze pilots used to have their funerals before they left for the mission.

 

[dfb]

I think Litchi is using Google Maps data. Google elevations are accurate to +- 30 feet. If you are in developed areas, structures are averaged in with ground elevations. Test before you commit to a mission, or be ready to abort and fly manually.

 

[Former Member]

I think Litchi is using Google Maps data. Google elevations are accurate to +- 30 feet. If you are in developed areas, structures are averaged in with ground elevations. Test before you commit to a mission, or be ready to abort and fly manually.

Agree. I always fly the mission manually before I Litchi it.

 

[caleb1]

The actual ground elevations are probably accurate to within a few meters, but do not take into account the height of vegetation, and you cannot trust the aircraft relative altitude to better than a few meters either. All the altitudes that are defined relative to ground level are converted by Litchi to elevations relative to the takeoff point, since the aircraft does not have a good measure of absolute altitude at takeoff. I would be very concerned about the descent to WP 52, for example, with trees at the edge of the water.

I see what you are saying. WP51 is set to about 180 ft, and is the last waypont over trees until WP 58. I can understand how the green stuff between WP 51 and 52 might look like trees, and I would think that too if I had not been there in person before to know that it's actually just marsh and reeds... I would probably be safer if I just set an above ground altitude of about 35 feet for waypoints 52 - 56. Instead of 26... Any ideas on if that would be safer? (I said I had set them to 16 in my original post but that was incorrect. I had them set to 26)

If you are religious man, you might want to recite a prayer before the voyage. Kamikaze pilots used to have their funerals before they left for the mission.

With you 100% on that one. ;-) Maybe buying drone ins would be a good idea too

Agree. I always fly the mission manually before I Litchi it.

I would do that, but at altitudes that low, I would not have signal at that location to do so...

 

[theDRONEranger]

I especially liked the part where you say . . .

These waypoints are going to be somewhere where I cannot see with human eyes, and the signal will most likely disconnect (due to the low altitude), . . .

Be careful! Be verrryy careful!!! That is not a plan I would fly, especially after advertising. Just a recommendation, that's all.

 

[caleb1]

I especially liked the part where you say . . .

These waypoints are going to be somewhere where I cannot see with human eyes, and the signal will most likely disconnect (due to the low altitude), . . .

Be careful! Be verrryy careful!!! That is not a plan I would fly, especially after advertising. Just a recommendation, that's all.

Yes I see what you say, I have been reconsidering this mission. I might not do it.

 

[Former Member]

Yes I see what you say, I have been reconsidering this mission. I might not do it.

I was thinking about your mission. Is there a way to break it up into 2 missions? Fly one, and then drive or hike closer to the second part and launch again? Thats what I do.