Litchi Software- Am I Understanding this Correctly

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I know that Litchi considers where one takes off to be altitude zero. I want to set up a mission. So I followed my drone to two pastures up from my house, over 2 sets of trees. Hovering just over the tall grass (hay) the monitor read 75 feet (altitude). I landed the drone. Took off again and it reset altitude to zero. Is that what it does? I then ascended to above the trees and it read 115 feet. I assume I need to add the 75 feet (hovering over the grass). The 75 feet being the altitude from my base (outside my garage). So the mission would take me over the two stands of trees then ascend to 75+115=190 feet (to be over the trees) if I set the mission from outside my garage? Am I thinking of this correctly? Is there an easier way? Thanks in advance.
 
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I know that Litchi considers where one takes off to be altitude zero. I want to set up a mission. So I followed my drone to two pastures up from my house, over 2 sets of trees. Hovering over the tall grass (hay) the monitor read 75 feet (altitude). I landed the drone. Took off again and it reset altitude to zero. Is that what it does? I then ascended to above the trees and it read 115 feet. I assume I need to add the 75 feet (hovering over the grass). The 75 feet being the altitude from my base (outside my garage). So the mission would take me over the two stands of trees then ascend to 75+115=190 feet (to be over the trees) if I set the mission from outside my garage? Am I thinking of this correctly? Is there an easier way? Thanks in advance.
It sounds like your mission will take you up a slope or hill that is about 75 feet higher than than your house? If so, then yes you will need to factor that in. I've read numerous threads of losses due to miscalculating the height of the trees due to hills and slopes.
 
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Usually trees do not exceed 30m (90ft) in high if you not have a sequoia in front of your house. That's for orientation only.
And if you still not sure about those trees, fly your drone over them and see what altitude would be safe enough.
 
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Yes, you have to consider the height of all obstacles relative to your take-off point.
And, you have the option to use "Above Ground" for your waypoints in which case Litchi will check a data base for the elevation (msl) at the point of the waypoint and add your assigned altitude to that. It will not account for any grading since the database was created nor will it account for vegetation or man made structures.

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Very interesting having just installed Litchi and yet to fly anything other than FVP.
 
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My last Litchi waypoint mission had my takeoff point higher (AGL) than any of the 28 waypoints (ground level). The entire flight the Litchi lady was using the word "below" altitude the whole way. Pretty accurate but disconcerting to say the least.
 
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My last Litchi waypoint mission had my takeoff point higher (AGL) than any of the 28 waypoints (ground level). The entire flight the Litchi lady was using the word "below" altitude the whole way. Pretty accurate but disconcerting to say the least.

I have been fly Litchi Waypoints since Jan 2016. Litchi works GREAT! Negative altitude reports still scares my wife, and still makes me concentrate and tell myself (during the flight) it's OK, that is what I programed it to do
 
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Yes, you have to consider the height of all obstacles relative to your take-off point.
And, you have the option to use "Above Ground" for your waypoints in which case Litchi will check a data base for the elevation (msl) at the point of the waypoint and add your assigned altitude to that. It will not account for any grading since the database was created nor will it account for vegetation or man made structures.

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I would add my usual caveat about “above ground” for info. May seem obvious but...

Litchi calculates above ground at waypoints only. Not continuously along the path. So if, for example, there is a big bump in terrain between waypoints, the aircraft will not adjust height. So if the terrain is variable like that, be sure to add enough waypoints to “sample” enough terrain.
 

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