Yet another Litchi Height Question...

[Qoncussion]

So, if I create a new Litchi mission by manually flying the mission, I would guess that all altitude (height) points would be relative to the home point. Is this correct? If so, would I need to always launch from the exact same point before activating the mission to ensure that my altitudes are the same from one flight to the next?

There is a particular shot that I want to get several times over several months. It's up in the Sierra Nevada Mountains. A couple of the waypoints will be a relatively tight squeeze between two hillsides - with a minimal margin for vertical error. As one hill jets out over the other, and I'll be flying under this. I fly through this space (manually) often with no problems.

So then - a few months pass, and now my launching point has 12+ feet of snow. So I'm 12 feet higher than in the summer. Will all waypoints now be 12 feet higher? I hope that makes sense.

 

[wxperson]

Yes.

The elevation is based off of the takeoff level of the drone... now 12 feet (ASL) higher.

 

[Qoncussion]

Yes.

The elevation is based off of the takeoff level of the drone... now 12 feet (ASL) higher.

That's what I thought. Thanks - I'll plan accordingly.

 

[MAStetz]

Yes.

The elevation is based off of the takeoff level of the drone... now 12 feet (ASL) higher.

Would this still be the case if the mission was created with altitudes relative to ground?
I'm thinking no, well at least I hope not as I'm working on a similar project over the next 12 months.

 

[wxperson]

It is always based from the takeoff point. You can change your waypoints to accommodate elevation changes. i.e. if you take off from 1000 ASL and want to maintain an above ground height of 400' (for example)... if you have a waypoint that has a ground elevation of 900' ASL then you can set that point at 300'... a ground elevation of 1100 ' ASL would have a waypoint height of 500' . in all 3 cases you would remain at 400' above ground level.

 

[Qoncussion]

I found this very helpful thread on PhantomPilots: Litchi Mission Hub Ground Elevation

@MAStetz - it does appear that you can (now) set waypoint altitudes relative to ground. I live in the mountains, and am not quite ready to trust the hub map elevations, as the terrain changes every few feet in some of my flying locations. That said, I will be testing this further to figure out the best methods for implementing all of this tech in my missions.

 

[wxperson]

I found this very helpful thread on PhantomPilots: Litchi Mission Hub Ground Elevation

@MAStetz - it does appear that you can (now) set waypoint altitudes relative to ground. I live in the mountains, and am not quite ready to trust the hub map elevations, as the terrain changes every few feet in some of my flying locations. That said, I will be testing this further to figure out the best methods for implementing all of this tech in my missions.

you can set them with ground elevation ASL in mind but the number you associate with a waypoint is still relative to take off point

 

[Qoncussion]

you can set them with ground elevation ASL in mind but the number you associate with a waypoint is still relative to take off point

If I understand you ~ at the end of the day everything is still tied to the home point? So in my original question (top of thread), I'm still looking at a 12 foot variance at my home point between summer (dry ground at home point), and winter (12 feet of snow at home point) ~ and therefore ~ a 12 foot variance at each waypoint... Correct?

 

[MAStetz]

It is always based from the takeoff point. You can change your waypoints to accommodate elevation changes. i.e. if you take off from 1000 ASL and want to maintain an above ground height of 400' (for example)... if you have a waypoint that has a ground elevation of 900' ASL then you can set that point at 300'... a ground elevation of 1100 ' ASL would have a waypoint height of 500' . in all 3 cases you would remain at 400' above ground level.

I beg to differ, and i will test this theory out very easily, I will set Waypoint 1 at roof height of building off to the side, i will set that waypoint to 15' RTG (relative to ground, approx height of roof peak) and launch my mavic we all know it will hover next to building @ about 15'. I will then proceed down the ravine next to building approx 10' down, then launch mavic and upload mission, I'm pretty sure it will go to waypiont 1 at roof level. if not it will be about 5' off the ground.

 

[MAStetz]

If I understand you ~ at the end of the day everything is still tied to the home point? So in my original question (top of thread), I'm still looking at a 12 foot variance at my home point between summer (dry ground at home point), and winter (12 feet of snow at home point) ~ and therefore ~ a 12 foot variance at each waypoint... Correct?

No i believe this is incorrect IF you set your waypoints relative to ground, only in the app, mission hub on the web doesn't support this. it received the altitudes from google not your home point so it doesn't care about your home point when you run the mission, the data for altitude was from google. I will be testing this theory and post my results

 

[Qoncussion]

I will be testing this theory and post my results

Please do ~ I'm eager to know

 

[wxperson]

its in the manual

Waypoint Settings

• Altitude: The altitude of the waypoint relative to the elevation of the aircraft where it took off. The waypoint's altitude is also shown above the waypoint marker on the map.
  
  

 

[TheoMatthias]

you can set them with ground elevation ASL in mind {snip}...

In aviation, altitude is expressed with reference to MSL (mean sea level) or AGL (above ground level); there is no ASL. I assume you are referring to MSL and not AGL?

If I am on the top of a 7,000-ft mountain and am flying my Mavic 350-ft above the home point, the Mavic's altitude is 350-ft AGL but is 7,350 MSL. And then there is density altitude...but that's another topic!

 

[MAStetz]

its in the manual

Waypoint Settings

• Altitude: The altitude of the waypoint relative to the elevation of the aircraft where it took off. The waypoint's altitude is also shown above the waypoint marker on the map.

I agree with this, I think the confusion is rerunning the mission, once you have created the mission it's only going to repeat the mission as it ran the first time, it's not going to look back at home point altitude and recalculate thus if @Qoncussion reruns his mission it's not going to add 12' feet of snow that he may be standing on, it's going to run the mission with the altitudes already stored in the saved mission.
testing of this theory will commence tomorrow.

*EDIT*
that is if all waypoint are set RTG in the app please note RTG is found only in the app not in web based mission hub

 

[TheoMatthias]

{snip}... it's going to run the mission with the altitudes already stored in the saved mission.
testing of this theory will commence tomorrow {snip}...

Very interested in the outcome of this testing. Thanks!

 

[wxperson]

In aviation, altitude is expressed with reference to MSL (mean sea level) or AGL (above ground level); there is no ASL. I assume you are referring to MSL and not AGL?

If I am on the top of a 7,000-ft mountain and am flying my Mavic 350-ft above the home point, the Mavic's altitude is 350-ft AGL but is 7,350 MSL. And then there is density altitude...but that's another topic!

with reference to my post ASL was Above Sea Level

 

[gustofusion]

Just be aware that in Improved areas for example a side walk in a city when given an altitude above sea level will be more accurate than let's say a flat area on a mountainous area in a rural setting. The areas in more urban environments will have more accurate attributes in regards to topographic data recorded that can be referenced. So altitude above ground level in known measured areas in urban environment will be more accurate than in rural areas where topographic data may not always be current.

An example would be, an area has been graded to allow for construction, street planning etc may not have updated topo data and the accuracy may be off. Now Litchi will give the elevation per waypont in reference to the first waypoint, but if the referencing topo data is old, inaccurate or otherwise there will be deviation in the flight altitude, so always allow yourself a margin of error when planning a flight.

 

[MAStetz]

@Qoncussion @wxperson @TheoMatthias The testing has concluded and the results are RTG is NOT relative to ground it is relative to WP 1 which is relative to homepoint altitude So the height setting relative to ground in the App is misleading it also means @Qoncussion needs to take a shovel with him to remove 12' feet of snow, but don't feel bad as i have 4 month's of video (8 videos total shot twice a month) that have different home point altitudes of about 6' that is going to make a huge video blending headache.

 

[Qoncussion]

@Qoncussion @wxperson @TheoMatthias The testing has concluded and the results are RTG is NOT relative to ground it is relative to WP 1 which is relative to homepoint altitude So the height setting relative to ground in the App is misleading it also means @Qoncussion needs to take a shovel with him to remove 12' feet of snow, but don't feel bad as i have 4 month's of video (8 videos total shot twice a month) that have different home point altitudes of about 6' that is going to make a huge video blending headache.

Ok, you have confirmed what I thought. Thanks a bunch for testing this! I'm heading out to buy a shovel now...

 

[gustofusion]

My experience has been different when setting RTG missions. The altitude deviation can be reviewed in Google earth too.