Eagle Tree and altitude

[Trnquill]

I have had very poor results with EagleTree what it comes to altitude logging/display. Is it just me or is this a common problem? I have datalogger v3 and OSD expander (not the pro), all software & firmware versions are up to date.

I first bought the Altitude Microsensor and had https://www.helifreak.com/showthread.php?t=159351 with it from day one. I have still not receivad an answer of ANY KIND from EagleTree in addition to one "what software versions are you using?" reply. After that no answer (other than auto-replies) to my several emails. And it's been two weeks now. Some customer service, I say.

I just recently got hold of the EagleTree GPS v3 expander and gave it a go. Distance, speed etc. work very nice but again the altitude is off the chart. Usually the alititude wanders between -20 and +20 meters when the heli is sitting still on the ground. In the air the altitude shows values between 0 and ~70 meters with no apparent relation to real flying altitude. Once the altitude was around -1600 meters for the entire flight (I have checked "start from zero" on OSD altitude settings).

There are 8 to 10 satellites available at all times. I live in Finland which might affect the resolution and accuracy of altitude information. Finland is so far north all the GPS satellites sit just above the horizon making 3D measurements a bit tough for any GPS. But nevertheless, I'm far from impressed with EagleTree altitude metering and their "customer support". What kind of experience do you have on altitude measuring with EagleTree?

[Danal Estes]

Originally Posted by Trnquill

Finland is so far north all the GPS satellites sit just above the horizon making 3D measurements a bit tough for any GPS.

GPS satellites are not in equatorial orbits. Your longitude doesn't matter.

[Trnquill]

Originally Posted by Danal Estes

GPS satellites are not in equatorial orbits. Your longitude doesn't matter.

Oh, you're absolutely right! Didn't know about that. The Wikipedia animation you posted clarifies it once and for all! So, one excuse less for GPS altitude on sucking.

[ChrisH]

Well that is an AWESOME animation Danal ... Wikipedia is awesome.

[Danal Estes]

Originally Posted by Trnquill

So, one excuse less for GPS altitude on sucking.

Exactly! It really ought to be better than that. But... most GPS chipsets are not all that accurate in altitude. This is one reason why Full Scale aircraft GPS approaches come in flavors of precision, where the high-precision approaches require an augmented GPS signal. WAAS or similar.

Anyway, doesn't really help you... altitude is hard to get from GPS. I'm wondering what the best "plumbing" is for a barometric sensor, to put a "static port" on a helicopter.

[halley]

Originally Posted by Danal Estes

altitude is hard to get from GPS. I'm wondering what the best "plumbing" is for a barometric sensor, to put a "static port" on a helicopter

Barometric altitude is notoriously tricky too, until you get quite far from the surface. And that's not counting the fact that your whole craft is in a variable downdraft with vortices. It might end up being a "don't take two compasses to sea" situation, comparing GPS and barometric results.