Litchi base altitude.

[8364kHz]

I am using Litchi.

The web site states:-

"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."

At waypoint 1 before the drone takes off, it is sitting on the ground and it is at an altitude of 230m. If I then set the altitude to of waypoint 1 to 30m, the drone will rise to 260m (230AMSL) + 30m.

My question is, What is the reference altitude, 230m, the drone on the ground or the waypoint 1 altitude of 260m?



There appear to be other inconsistencies with Litchi waypoint mission planning with gimbal elevation when pointing at a POI. I have a particular mission where the drone is above the POI but the gimbol is pointing at +9 degrees.



I have asked this question before but I am still confused (could be an age thing).

I crashed my P4Pro today because of altitude problems. Fortunately only prop damage.



Also, can I now class myself as an experienced pilot (if lessons are learned) now that I have survived my first crash?

 

[tevek]

I am using Litchi.

The web site states:-

"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."

At waypoint 1 before the drone takes off, it is sitting on the ground and it is at an altitude of 230m. If I then set the altitude to of waypoint 1 to 30m, the drone will rise to 260m (230AMSL) + 30m.

My question is, What is the reference altitude, 230m, the drone on the ground or the waypoint 1 altitude of 260m?



There appear to be other inconsistencies with Litchi waypoint mission planning with gimbal elevation when pointing at a POI. I have a particular mission where the drone is above the POI but the gimbol is pointing at +9 degrees.



I have asked this question before but I am still confused (could be an age thing).

I crashed my P4Pro today because of altitude problems. Fortunately only prop damage.



Also, can I now class myself as an experienced pilot (if lessons are learned) now that I have survived my first crash?

The altitude of the 1st WP is relative to the height of where the quad took off from, which is essentially zero as a reference point. The height of the first WP in your case is 30 mtrs relative to where home point was recorded and where your mission commenced. If your surrounding obstacles are lower than that, you will be fine, if not, there will be grief.
As for the gimbal actions during the mission, you can adjust that in the mission settings. I don't have my device at the moment to send you a screen shot but if your POI is higher than your WP mission, that may also explain it.
As for being an experienced pilot after your first crash, I have a shed full of broken planes, gliders, helos and quadcopters, so we are both experienced lol.

 

[8364kHz]

Thank you.
As I now understand it , it is the point on the ground before take off.
Now to get a spreadsheet done and I wish Google Earth was more accurate. Looking into Lidar data.

John.

 

[tevek]

Thank you.
As I now understand it , it is the point on the ground before take off.
Now to get a spreadsheet done and I wish Google Earth was more accurate. Looking into Lidar data.

John.

Yes it is. I only use google data and the app heights as a guide and add 10% to be safe.

 

[The Springs]

Its not just a matter of inaccurate GE elevations when planning a mission . I have noticed the elevation can change when running the same mission on different days .So you have to be wary.

 

[8364kHz]

Agree, very wary.
I had a successful mission today with 25 way points, uphill and down hill. I worked it out on a spreadsheet first ofall and all went smoothly.
Solved a problem whith record not restarting by introducing a delay for 3 seconds to allow gimbol to relocate.

John.

 

[dolphindancer]

The altitude of the 1st WP is relative to the height of where the quad took off from, which is essentially zero as a reference point. The height of the first WP in your case is 30 mtrs relative to where home point was recorded and where your mission commenced. If your surrounding obstacles are lower than that, you will be fine, if not, there will be grief.
As for the gimbal actions during the mission, you can adjust that in the mission settings. I don't have my device at the moment to send you a screen shot but if your POI is higher than your WP mission, that may also explain it.
As for being an experienced pilot after your first crash, I have a shed full of broken planes, gliders, helos and quadcopters, so we are both experienced lol.

tevek

I'm still a bit confused with Litchi's relative to ground waypoint altitude mode. Perhaps the best way to describe my confusion is an example of a proposed mission.

I've created a 4 waypoints to be flown.
WP1 flight altitude 200mtrs above sea level
WP2 flight altitude 250mtrs above sea level
WP3 flight altitude 190mtrs above sea level
WP4 flight altitude 150mtrs above sea level

Using sub centimeter GPS Survey Equipment, I determine that
the drone takeoff (home point) point elevation is 50mtrs above sea level.

If I understand your post correctly, I should tell the drone that the first waypoint's (AGL) altitude will be 150mtrs?

Then the drone will automatically climb 50mtrs to the next waypoint?

Then descend 60mtrs to the next?

Then descend 40mtrs to the next?

I think I'm on the right track but appreciate your counsel.

Thanks
DD

 

[tevek]

tevek

I'm still a bit confused with Litchi's relative to ground waypoint altitude mode. Perhaps the best way to describe my confusion is an example of a proposed mission.

I've created a 4 waypoints to be flown.
WP1 flight altitude 200mtrs above sea level
WP2 flight altitude 250mtrs above sea level
WP3 flight altitude 190mtrs above sea level
WP4 flight altitude 150mtrs above sea level

Using sub centimeter GPS Survey Equipment, I determine that
the drone takeoff (home point) point elevation is 50mtrs above sea level.

If I understand your post correctly, I should tell the drone that the first waypoint's (AGL) altitude will be 150mtrs?

Then the drone will automatically climb 50mtrs to the next waypoint?

Then descend 60mtrs to the next?

Then descend 40mtrs to the next?

I think I'm on the right track but appreciate your counsel.

Thanks
DD

You're on the right track with the exception of the reference to the 'above sea level'. The WPs are referenced to your take off AGL point. Each of the actions you've listed are essentially correct when you batch edit 'relative to ground', as the drone will ascend and descend along the way once you have entered the first WP height.
Using your example, if you set 200 Mtrs as your first WP, Litchi will automatically calculate the remaining WP heights WRT to your take off point, regardless of whether you are at the beach, in the hills or out in the desert. Just need to be aware of the terrain before you load the mission to avoid trees, manmade structures etc as the drone has no idea of what's beneath it.

 

[dolphindancer]

You're on the right track with the exception of the reference to the 'above sea level'. The WPs are referenced to your take off AGL point. Each of the actions you've listed are essentially correct when you batch edit 'relative to ground', as the drone will ascend and descend along the way once you have entered the first WP height.
Using your example, if you set 200 Mtrs as your first WP, Litchi will automatically calculate the remaining WP heights WRT to your take off point, regardless of whether you are at the beach, in the hills or out in the desert. Just need to be aware of the terrain before you load the mission to avoid trees, manmade structures etc as the drone has no idea of what's beneath it.

tevek

Thanks. Really appreciate your counsel. I now understand that the first waypoint height is key.

I used sea level altitude to demonstrate the need to know the elevation of the takeoff point is--relative to that datum--if one is going to plan a mission that refers to it.

I have a project that requires the drone fly at altitude of 146mtrs above sea level. Before flying that mission, I used survey grade sub-centimeter GPS equipment to determine what the elevation of the takeoff (home) point of the drone was above the sea level datum .

That measurement revealed a takeoff point elevation of 63.55mtrs above sea level. Rounding off to 64mtrs, I set the first waypoint's AGL altitude at 82mtrs. Now the drone--using it's barometric chip--knows how far--in millibars of Hg--above the takeoff point it needs to climb to get the mission sea level altitude of 146mtrs. Since the drone uses changes in barometric pressure to determine elevation change, the 82mtr climb AGL will be approximate but just fine for the recon work intended.

So, much for my long winded sea level blah...

Thanks again for your counsel...made things clear

Cheers
DD