Litchi relative to ground - is altitudes shown "backwards"?

[marklyn]

The relative to ground feature is a great feature and I've used it a few times on missions where the elevation was minimal but I struggle with understanding the difference between the altitude take off point and when the drone flies down into a valley or river bed. An example below might help someone to clear up my understanding or logic of why the altitudes are shown the way they are...

Scenario: Take off point 1 is at 727' above sea level. Point 4 (over river) is at 495' above sea level. The difference is 232'.

Mission 1: Drone is set to 100' above point 1 and all my points are set the same, so entire mission is 100' above take off point. I understand this to mean that, at point 4, over the river the drone is now approximately 332' over the river, using numbers from scenario above. (see attachment 1 for mission)

Mission 2: Drone is set to 100' above point 1. Then I load this mission on my iPad tablet and use the wrench to select all points, edit and change to 101' relative to ground (instead of take off point). Now. I see point 1 is 101', which I expect. But point 4, right over the river, is -130'. So Litchi app is taking the 232' difference between point 1 and point 4 and subtracting the 101' that I want the drone over land/water, right?
(see attachment 2)

So this all boils down to one question. Wouldn't it be better/easier to see point 4 in a way that let's me know the drone is actually 101 feet from the water. Or maybe the little bubble could show me -130/101 meaning -130' lower than take off point altitude. I'm just having a hard time wrapping my head around some of these missions when I see a negative or lower number than the start point. It's like I want to see another number relative to the ground it's flying over to know I'm really high enough.
I'm going to write the Litchi people and see what they say but I'm interested in thoughts about this feature from the community.

 

[Qoncussion]

All elevations will always be relative to the takeoff point... period. There are no other options.

 

[marklyn]

All elevations will always be relative to the takeoff point... period. There are no other options.

I was really asking for some thoughts on this as a possible option or feature enhancement. The MP is pretty sophisticated and when you're flying in canyons, lake beds, etc., from a higher elevation point, it didn't seem too far of a stretch to have some way to tell that you *really* are a certain elevation above the ground.
It was just a thought.

 

[bjk896]

Could someone clarify what happens between waypoints. Does the AC fly straight line height to next waypoint or fly "relative to ground" all the way ?

 

[Qoncussion]

Could someone clarify what happens between waypoints. Does the AC fly straight line height to next waypoint or fly "relative to ground" all the way ?

The only aspect of the ground that is taken into account is your home point. From waypoint to waypoint it flies in a straight line. You can set different altitudes for each waypoint, and the craft will rise at a rate equal to the change in elevation; reaching the new elevation exactly upon reaching the next waypoint. But the craft's elevation relative to the changing ground below is not taken into consideration at all - except for the craft's hight relative to the home point.

 

[Jonny63]

If I start from an elevated position do I need to put in a negative height to descend down ?

 

[lisadoc]

If I start from an elevated position do I need to put in a negative height to descend down ?

From the home point. Below your initial ground start point - Yes.

Fly the route manually first, just to be sure you have everything correct. Or try it while making sure to take over if needed. But flying too high is always good. Flying too low - generally not.

 

[Brojon]

I would love love LOVE it if relative height tools were available in ANY online mapping software.
By that I mean click on a point then click on another to get a relative height difference. We have quite a few "wrinkles" in terrain here and it makes planning missions a real bugger given I can get a couple hunnerd feet variation in very little linear travel. Right now I export and convert to KML and import into Google Earth and adjust by eyeball which is highly time consuming.