Litchi Waypoints: Altitude vs Above Ground

[SandmanSGD]

Apologies.

I realize this has been covered numerous times, as I've likely read all of the responses, but it's still not crystal for me (total noob).

Some threads on this were posted before the 'Above Ground' feature came out, some after, and a couple since the feature was recently updated? Some address the app, some the mission hub, some through google earth. Now that I'm (almost) done whingeing about this, my question is, if i set these up in mission hub, and upload on site "relative to ground," which elevation will my drone be operating off of; the yellow one, or the white one!? Please tell me its the yellow one, and if it is, why have I been focusing on the white one for the last 5 hours? See pic for example.



Fwiw I'm attempting to set waypoints with POIs to record golf holes, tee to green. Unfortunately for me, my first course winds through a canyon, has 50-60ft trees near take-off/ landing points, more than a few multi-million dollar homes on every hole, and I need to figure out how to fly this thing smoothly 20-30ft off the not-so-flat ground. Below is my first attempt the other week. Lol.

What the video doesn't show is me ditching the drone into a small mountain and snapping three props after the first (!) green, and abandoning all but one other mission (also featured ?‍). The drone height is seemingly higher than I would like most of the time, you know... until it's the opposite. I realize I'm not working with entirely reliable data, but I'm confident that's not the main issue here..... I think I'm getting close tho. Any feedback would be great. Thanks.

 

[Fly Dawg]

Please tell me its the yellow one, and if it is, why have I been focusing on the white one for the last 5 hours? See pic for example.

That it actually a blue line, not white. The yellow line marks the waypoints. The blue line is the radius of the curved turn. It will not be there if you use straight lines. When using curved turns, the aircraft never actually reaches the set waypoint, and any " actions" you have set are ignored. "Actions" will only work with straight lines.

 

[sar104]

Litchi "above ground level" mode is slightly misnamed, because even though mission hub will calculate the waypoint heights relative to the ground, the mission that is uploaded to the aircraft has waypoint altitudes that are all relative to the takeoff point. Since the first altitude specified for a mission is the altitude at waypoint 1, if the ground elevation at the takeoff point is not the same as the ground elevation under waypoint 1 then all waypoint altitudes will be off. So - in any kind of variable elevation terrain you need to set the first waypoint directly over the takeoff location.

On your map, the first elevation (yellow) is the height above ground, and the second elevation (white) is the height above the takeoff location - that's the height that actually gets uploaded to the aircraft for the mission.

 

[SandmanSGD]

That it actually a blue line, not white. The yellow line marks the waypoints. The blue line is the radius of the curved turn. It will not be there if you use straight lines. When using curved turns, the aircraft never actually reaches the set waypoint, and any " actions" you have set are ignored. "Actions" will only work with straight lines.

Thanks Fly Dawg. That's good info to know regarding actions. Sorry if I was confusing, but was referring to the white Above Ground number, and the yellow Altitude number. Good looking out!

 

[SandmanSGD]

....So - in any kind of variable elevation terrain you need to set the first waypoint directly over the takeoff location.

Ok, I was with you until this^, and thanks for responding. I've been under the impression that the first waypoint is already directly over the takeoff location; essentially, that the takeoff location and first waypoint are one in the same.
> I open mission hub
> I click where I want it to takeoff from
> Litchi "auto names" it waypoint 1.

What does"to be directly over the takeoff spot" mean?

On your map, the first elevation (yellow) is the height above ground, and the second elevation (white) is the height above the takeoff location - that's the height that actually gets uploaded to the aircraft for the mission.

This was what I was thinking originally, but my takeaway from this mission review (post crash), was seemingly due to my manipulating the Altitude (yellow#), to get my preferred AG elevation (white#), so much so that I brought the Altitude (yellow) to negative -37. Here's where it literally went down (between 6 and 7).


My original thinking (hope) was if the drone is working off the AG data (white#), the Altitude number (yellow) was relative to "WP1." See below pic of highlighted WP1.


Note that ground level elevation of WP7 is 67ft above ground level elevation of WP1, so if I punched in -37 for Altitude, in my mind, I was still at my preferred AG elevation (white=30/31). There's got to be something glaringly obvious I'm missing here related to my confusing takeoff location and WP1?

Thanks for any additional help. Excited for the "aha moment" I feel is close!!! BTW I've opted to do each hole separately now, which is kind of a bummer because I see the potential of doing 2-3 at a time and having a great "no-cut" shot.

 

[sar104]

Ok, I was with you until this^, and thanks for responding. I've been under the impression that the first waypoint is already directly over the takeoff location; essentially, that the takeoff location and first waypoint are one in the same.
> I open mission hub
> I click where I want it to takeoff from
> Litchi "auto names" it waypoint 1.

What does"to be directly over the takeoff spot" mean?

Just that waypoint 1, presumably, is in the air, not on the ground, and needs to be at the same location, coordinates, that you take off from. There is nothing that ensures that you take off from WP1 - you can take off from anywhere within 3 km (if I recall correctly) of WP1.

This was what I was thinking originally, but my takeaway from this mission review (post crash), was seemingly due to my manipulating the Altitude (yellow#), to get my preferred AG elevation (white#), so much so that I brought the Altitude (yellow) to negative -37. Here's where it literally went down (between 6 and 7).
View attachment 110625

My original thinking (hope) was if the drone is working off the AG data (white#), the Altitude number (yellow) was relative to "WP1." See below pic of highlighted WP1.
View attachment 110626

No - in AGL mode the yellow number is the height AGL and the white number is height relative to the takeoff point. You set the yellow number as the AGL you need and the white number is just for reference relative to takeoff.

Note that ground level elevation of WP7 is 67ft above ground level elevation of WP1, so if I punched in -37 for Altitude, in my mind, I was still at my preferred AG elevation (white=30/31). There's got to be something glaringly obvious I'm missing here related to my confusing takeoff location and WP1?

No - you have it backwards. You set the AGL elevation (yellow) with the slider or by typing in the altitude box. Ignore the white number. -37m in the altitude box (which is the yellow number) is underground.

Thanks for any additional help. Excited for the "aha moment" I feel is close!!! BTW I've opted to do each hole separately now, which is kind of a bummer because I see the potential of doing 2-3 at a time and having a great "no-cut" shot.

 

[SandmanSGD]

Just that waypoint 1, presumably, is in the air, not on the ground, and needs to be at the same location, coordinates, that you take off from. There is nothing that ensures that you take off from WP1 - you can take off from anywhere within 3 km (if I recall correctly) of WP1.



No - in AGL mode the yellow number is the height AGL and the white number is height relative to the takeoff point. You set the yellow number as the AGL you need and the white number is just for reference relative to takeoff.



No - you have it backwards. You set the AGL elevation (yellow) with the slider or by typing in the altitude box. Ignore the white number. -37m in the altitude box (which is the yellow number) is underground.

Aha! Thank you! That's all very, very solid info for me. (Am I dumb or is that just not as intuitive as one might think? Sorry to hit you with a couple more Qs but...

So I should be setting wp1 Alt. to '0', and proceed from there?

How am I ensuring drone and mission coordinates align? I've just been placing the drone on the ground where the little arrow drone icon in the mission, and the little arrow drone icon that represents the drone's current gps location, overlay.

 

[sar104]

Aha! Thank you! That's all very, very solid info for me. (Am I dumb or is that just not as intuitive as one might think? Sorry to hit you with a couple more Qs but...

So I should be setting wp1 Alt. to '0', and proceed from there?

How am I ensuring drone and mission coordinates align? I've just been placing the drone on the ground where the little arrow drone icon in the mission, and the little arrow drone icon that represents the drone's current gps location, overlay.

No - you can't do a zero height waypoint, and that's not necessary - it's just necessary that the the ground elevation under WP1 is the same as the elevation of the takeoff point. The easiest way to ensure that is to set WP1 at the takeoff point so that when the aircraft arrives at WP1 the relative height of the aircraft (height above takeoff point) is the same as the height AGL of WP1. Then everything is correctly referenced. It doesn't matter if WP1 coincides precisely with the takeoff point, as long as they have similar ground elevation.

If you don't know exactly where you are going to take off from then the simplest solution is to set a spare waypoint as WP1 and then position it to your location it when you get to your chosen takeoff point.

There is really no other way for this to work, but it's definitely not completely obvious or intuitive, so I wouldn't feel too bad about it.

 

[SandmanSGD]

No - you can't do a zero height waypoint, and that's not necessary - it's just necessary that the the ground elevation under WP1 is the same as the elevation of the takeoff point. The easiest way to ensure that is to set WP1 at the takeoff point so that when the aircraft arrives at WP1 the relative height of the aircraft (height above takeoff point) is the same as the height AGL of WP1. Then everything is correctly referenced. It doesn't matter if WP1 coincides precisely with the takeoff point, as long as they have similar ground elevation.

If you don't know exactly where you are going to take off from then the simplest solution is to set a spare waypoint as WP1 and then position it to your location it when you get to your chosen takeoff point.

There is really no other way for this to work, but it's definitely not completely obvious or intuitive, so I wouldn't feel too bad about it.

Sar- thanks for all the help! I think the litchi people could be more clear in their user guide in a couple areas, but maybe this is what I get for skipping GO app for beginners.

Well, I've bombarded you enough, so just know I definitely appreciate your patience and quick/ clear responses. I am feeling however, like I do know exactly where I'm going to take off from (very specific tees per hole mission), but perhaps I'm using 'exactly' too casually.


I'll give setting WP1 at the mission sites a try. I thought I saw a YT demo on batch editing WPs Alts to ground elevation in app settings, which makes me think it will accomplish what your talking about. We'll see how it goes tomorrow! Will post our final product vid(s) in the future, because this is project is definitely happening regardless of how long it takes me. ?

Thanks again.

 

[sar104]

Sar- thanks for all the help! I think the litchi people could be more clear in their user guide in a couple areas, but maybe this is what I get for skipping GO app for beginners.

Well, I've bombarded you enough, so just know I definitely appreciate your patience and quick/ clear responses. I am feeling however, like I do know exactly where I'm going to take off from (very specific tees per hole mission), but perhaps I'm using 'exactly' too casually.
View attachment 110635

I'll give setting WP1 at the mission sites a try. I thought I saw a YT demo on batch editing WPs Alts to ground elevation in app settings, which makes me think it will accomplish what your talking about. We'll see how it goes tomorrow! Will post our final product vid(s) in the future, because this is project is definitely happening regardless of how long it takes me. ?

Thanks again.

OK - but just to be clear - there's more than one potential pitfall. Your original problem was because you thought that you needed to make the white number the appropriate height AGL, when in fact it's the yellow number. If you create a mission and add waypoints you will notice that, by default, the mission hub will add them all at the same height AGL - whatever is set in the box/slider. You can batch edit all waypoints to the same height AGL by selecting them all and then checking the "above ground" box and/or setting the height AGL for the waypoints.

The other issue is correctly referencing all the waypoint heights in the data uploaded to the aircraft, which is achieved by taking off from the same elevation as the ground elevation at WP1.

 

[airnocker]

Aha! Thank you! That's all very, very solid info for me. (Am I dumb or is that just not as intuitive as one might think? Sorry to hit you with a couple more Qs but...

So I should be setting wp1 Alt. to '0', and proceed from there?

How am I ensuring drone and mission coordinates align? I've just been placing the drone on the ground where the little arrow drone icon in the mission, and the little arrow drone icon that represents the drone's current gps location, overlay.

I'd like to know this myself as a newbie to Litchi and preparing my first proof-of-concept missions. I was going on what appears to be an incorrect assumption that if I set Waypoint 1 where I intended to take off from that the 101ft "Altitude" parameter value for Waypoint 1 was the "Start, ascent" target altitude. One can see in the image of my Waypoint 1 that the small print "Ground Elevation: 5233ft (Oft below first waypoint)" stays at zero below first waypoint when Above Ground is checked regardless of the Altitude value. So now I'm unclear what it takes to start at a designated Waypoint 1, lift off straight up to a target altitude before embarking to the next waypoint.

Does it require setting the first Waypoint where take off is intended, create a 2nd waypoint nearby but then copy the Latitude and Longitude values from the 1st to the 2nd Waypoint, then set the Altitude of the 2nd waypoint to be 101ft and Above Ground checked? Then, where my current Waypoint 2 is in the screenshot becomes Waypoint 3. Am I understanding this correctly?

When using curved turns, the aircraft never actually reaches the set waypoint, and any " actions" you have set are ignored. "Actions" will only work with straight lines.

I believe another explanation of this behavior if I'm understanding this correctly is that Waypoint "Actions" will only be performed when their waypoints are at the start or end of straight line segments. This is critically important information, so thank you Fly Dawg.

I appreciate any further input to this discussion thread.

 

[sar104]

I'd like to know this myself as a newbie to Litchi and preparing my first proof-of-concept missions. I was going on what appears to be an incorrect assumption that if I set Waypoint 1 where I intended to take off from that the 101ft "Altitude" parameter value for Waypoint 1 was the "Start, ascent" target altitude. One can see in the image of my Waypoint 1 that the small print "Ground Elevation: 5233ft (Oft below first waypoint)" stays at zero below first waypoint when Above Ground is checked regardless of the Altitude value. So now I'm unclear what it takes to start at a designated Waypoint 1, lift off straight up to a target altitude before embarking to the next waypoint.

No - that's correct. If you launch from that location the aircraft will simply ascend 101 ft to the first waypoint. If you launched 50 ft to the west, from the same elevation, it would also work fine - it would climb 101 ft and move 50 ft east to WP1.

But, for example, if the terrain varied at that location, and you launched nearby from an elevation 50 ft lower, then the aircraft would still only climb 101 ft and move to the first waypoint (because in the uploaded mission, all waypoint elevations are defined relative to the launch point by the white number in parenthesis), so rather than being 101 ft AGL at WP1, it would only be 51 ft AGL.

Does it require setting the first Waypoint where take off is intended, create a 2nd waypoint nearby but then copy the Latitude and Longitude values from the 1st to the 2nd Waypoint, then set the Altitude of the 2nd waypoint to be 101ft and Above Ground checked? Then, where my current Waypoint 2 is in the screenshot becomes Waypoint 3. Am I understanding this correctly?

I don't understand what you would be trying to achieve there - if WP1 and WP2 have the same lat/long, then they are in the same place.

 

[airnocker]

I'd like to know this myself as a newbie to Litchi and preparing my first proof-of-concept missions. I was going on what appears to be an incorrect assumption that if I set Waypoint 1 where I intended to take off from that the 101ft "Altitude" parameter value for Waypoint 1 was the "Start, ascent" target altitude. One can see in the image of my Waypoint 1 that the small print "Ground Elevation: 5233ft (Oft below first waypoint)" stays at zero below first waypoint when Above Ground is checked regardless of the Altitude value. So now I'm unclear what it takes to start at a designated Waypoint 1, lift off straight up to a target altitude before embarking to the next waypoint.

Does it require setting the first Waypoint where take off is intended, create a 2nd waypoint nearby but then copy the Latitude and Longitude values from the 1st to the 2nd Waypoint, then set the Altitude of the 2nd waypoint to be 101ft and Above Ground checked? Then, where my current Waypoint 2 is in the screenshot becomes Waypoint 3. Am I understanding this correctly?

I think I just answered my question by doing a quick mission edit. Having Waypoint 1 on the ground and a newly inserted Waypoint 2 at a higher altitude above ground that is a Lat/Long. copy of Waypoint 1 is the way to start at the first waypoint and rise to mission target altitude above ground to the 2nd waypoint before embarking on the rest of the waypoint circuits. If anyone would like screenshot examples of this let me know.

.

 

[airnocker]

No - that's correct. If you launch from that location the aircraft will simply ascend 101 ft to the first waypoint. If you launched 50 ft to the west, from the same elevation, it would also work fine - it would climb 101 ft and move 50 ft east to WP1.

Thanks sar104 for your fast response, but my KML exports to Google Earth seems to show the ascent from WP 1 to target altitude occurs along the flight path to WP 2, shown here.

I don't want this result shown above as my first mission KML result.

But when I insert a new WP after WP 1, as my last post described, it looks like what I'd expect, begin mission at or very near WP1, vertically climb to 100ft AGL where WP 2 is defined, same Lat/Long. but at 100ft AGL, shown here:

This KML screenshot depicts the way I thought the first version of this mission would do, and is what I want.

But, for example, if the terrain varied at that location, and you launched nearby from an elevation 50 ft lower, then the aircraft would still only climb 101 ft and move to the first waypoint (because in the uploaded mission, all waypoint elevations are defined relative to the launch point by the white number in parenthesis), so rather than being 101 ft AGL at WP1, it would only be 51 ft AGL.

I don't understand what you would be trying to achieve there - if WP1 and WP2 have the same lat/long, then they are in the same place.

I definitely understand what you are saying here, thanks. So do my screenshot examples help you see what I am trying to achieve?

Shoot, now I edited a variation to this last mission doing as sar104 indicated with WP 1, and the KML file indicates a straight up lift off from WP 1 to target altitube AGL then proceeds to WP2. Now I have to figure out why I get two different results on my initial mission creations. For now I'm chalking it up to "newbie here, doah!".

 

[sar104]

Thanks sar104 for your fast response, but my KML exports to Google Earth seems to show the ascent from WP 1 to target altitude occurs along the flight path to WP 2, shown here.

View attachment 110637
I don't want this result shown above as my first mission KML result.

But when I insert a new WP after WP 1, as my last post described, it looks like what I'd expect, begin mission at or very near WP1, vertically climb to 100ft AGL where WP 2 is defined, same Lat/Long. but at 100ft AGL, shown here:

View attachment 110638
This KML screenshot depicts the way I thought the first version of this mission would do, and is what I want.



I definitely understand what you are saying here, thanks. So do my screenshot examples help you see what I am trying to achieve?

Why not just put WP1 at the target altitude?

 

[airnocker]

sar104, the screenshots I posted were from my initial mission creations, so at first, I did not know or understand the importance or significance of have the "Above Ground" box checked. I'm now getting the impression that because my first mission that did not have the box checked the resulting KML screenshot showed a gradual ascent from "home" launch altitude of Waypoint 1 to Waypoint 2 and that this was solely due to my not checking the "Above Ground" box of Waypoint 1.

Once I modified all my original waypoints to have the "Above Ground box checked, the exported KML file seemed to show an immediate vertical ascent from Waypoint 1 to mission "altitude" prior to proceeding to Waypoint 2.

Thanks for you help in making this mission waypoint properties behavior clear to me.

 

[bsartist]

I’d like to add a few cents to this. Be sure you are placing enough waypoints over uneven terrain. Litchi will only calculate the AGL wherever there is a waypoint. And the aircraft will ascend smoothly in a straight line to the next waypoint (assuming it’s higher - or descend smoothly if it’s lower). If there is intervening high terrain it could hit it.

 

[sar104]

I’d like to add a few cents to this. Be sure you are placing enough waypoints over uneven terrain. Litchi will only calculate the AGL wherever there is a waypoint. And the aircraft will ascend smoothly in a straight line to the next waypoint (assuming it’s higher - or descend smoothly if it’s lower). If there is intervening high terrain it could hit it.

I can recall at least two lost aircraft events that I looked at here that were due to precisely that problem.

 

[airnocker]

I’d like to add a few cents to this. Be sure you are placing enough waypoints over uneven terrain. Litchi will only calculate the AGL wherever there is a waypoint. And the aircraft will ascend smoothly in a straight line to the next waypoint (assuming it’s higher - or descend smoothly if it’s lower). If there is intervening high terrain it could hit it.

Thanks Bill, your 2 cents are a valuable insight.

This has probably been discussed many times in the past, but shouldn't "Above Ground" be checked as the default?

 

[Fly Dawg]

but shouldn't "Above Ground" be checked as the default?

Not necessarily. It depends on the mission, and this feature has not been that long since added to Litchi. So you have to take the older versions that people are more used to in to account. Some may really use it. Others may have no need for it. Personally, I like having the option and not defaulting to AGL.