Height

[Sabreman]

I live in a mountainous area. It would appear that the height displayed of the AC in the IOS version 1.3 is versus the place of takeoff (or maybe the RC) & not the actual altitude? Does this mean the RTH setting is versus the take off location as well?

 

[sanderx]

Yes

 

[World Media]

Always has been

 

[Gregg Smith]

And what's fun is if you take off from a cliff and then fly down into a ravine the altitude actually goes negative. Very strange indeed. I did this once and it was weird to be flying at negative altitude. Also makes it hard to fly in hilly areas. I fly in an area in Austin where I take off and I'm over 100ftt at takeoff but some hills around me are higher and it requires you to be aware of the changing altitudes especially when they are slight and not drastic like in the mountains.

 

[Gregg Smith]

Yeah you need to be careful about it too because you can actually exceed 400' AGL even if you have your altitude limited to it. For instance, I fly from the roof of a 7 story building, roughly 90' AGL. When I takeoff the Inspire thinks it's at ground level. I handicap my altitude down to 300' max altitude because when the copter thinks it reached 300', it's actually at 390' AGL.

And you don't have compass errors flying from the building? I have a P3P and I have a tough time just flying from the ground or atop a parking garage.

 

[Machoman]

Conclusions:

1. There should be no alt limit in the RC as long it cannot calculate real alt over ground

2. Flying behind a hill and using rth after it or losing signal while having set 60 rth altitude will crash it into the trees.

3. Flying up a mountain will likely crash it when it stops ascending just over ground because of fictious alt limit

 

[Kilrah]

Know it and work with it, that's it... Won't change until FCs are capable of storing and handling gigs of worldwide terrain data onboard.

 

[Gregg Smith]

Conclusions:

1. There should be no alt limit in the RC as long it cannot calculate real alt over ground

2. Flying behind a hill and using rth after it or losing signal while having set 60 rth altitude will crash it into the trees.

3. Flying up a mountain will likely crash it when it stops ascending just over ground because of fictious alt limit

Actually if you take off from the top of a hill/mountain and you traverse down the mountain/hill and loose signal the quad would ascend to its RTH first, which if you took off from the top of a hill/mountain that is your 0 foot starting point. It would end up say 60 feet above your takeoff point. So it should be ok as long as the other hills are lower than where you started.

The reason is that if you take off from a higher advantage point as you descend you will see a negative height on your display. Very strange I know. But they don't take the actual height as seen by GPS and display it. It only knows that if you take off on a hill that's 0 starting height and if you fly down the hill you will see a negative value for your height. If the quad looses connection or you press RTH it will ascend to its height you programmed and RTH which means it will go above your starting point. Not just up say 60 feet from where it's at.

With that said you should always be in sight of course but there are times where I've been a couple hundred yards away from the quad and I've lost connection with it when flying in high density RF interference.