Elevation Reading when Lower than Takeoff

[jwmcgrath]

Curious, because this will be important when summer finally comes and we are at the lake...

If my takeoff point is higher than the level at which I'm flying, what is the elevation reading? I'm wondering if it shows NEGATIVE as I'd assume?

I don't have a lot of hills around to safely test the assumption and if anyone has insight I'd appreciate the foreknowledge...

Of course it plays a fairly serious role when trying not to hit trees, or the ground, or set a safe RTH altitude...


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[N017RW]

Yes.
When below the take off site elevation will be negative. This is based on atmospheric pressure and nothing to do with terrain.

 

[jwmcgrath]

Thank you... so yes, I should be prepared to do the math "on the fly" (pun certainly intended!)

If I take off 100' higher than my lowest intended flight altitude, and I observe a reading of -70 I should be 30' up... enough to clear the water skier and boat...

But will need a minimum 200' RTH altitude to clear the trees by 100' where "home" is.

Which is where the fun of metric/imperial rears its ugly head again.


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[N017RW]

Do not count on such accuracy from the on-board barometer. They are subject to drift and thermal errors.

 

[jwmcgrath]

Understood.

For the most part I plan on flying "line of sight"...

What I'm trying to preplan is "worst case" and "what-to-expect" scenarios, which you've been most helpful with.


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[OkiePhlyer]

Be sure and post video. That sounds like a cool place to fly.

 

[jwmcgrath]

Be sure and post video. That sounds like a cool place to fly.

High hopes for that...

We have a group of friends with seasonal trailers in a small family-run campground. Beautiful area.

We do a lot of tubing, skiing, wake-boarding, and there is a swimming hole the boats go to about 2200M away from the campground.

I got a P3S for Christmas and the goal is to become proficient enough between now and summer to capture good footage of all that.

I'll try Litchi for "following" the moving people, and for a waypoint mission to the swimming hole (since it's out of range of the P3S remote).

For the most part I'll launch from the beach. The campground is built on a hill, and my site is about 100' higher than that, and about 250' away... for the odd occasion I want to fly down to the beach, I just want to know what to prepare for!




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