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Old Aug 12, 2012, 04:23 PM
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United Kingdom, Southend-on-Sea
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Originally Posted by Vlodek9 View Post
Question,
Is there a way to 0 the GPS altitude when on the ground? Meaning, when I do my prechecks my altitude shows +\- 2-17 feet AGL and today I even got -25 feet AGL when I landed. So it would be helpful if there was a way to reset the altitude to 0 before take off (I think). Full scale aircraft have it.
just reset your home position, it's that simple
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Old Aug 12, 2012, 04:29 PM
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United States, AZ, Chandler
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Originally Posted by papa_lazerous View Post
just reset your home position, it's that simple
I do, prior to every flight. It does help a little and gets it +\- 2-5 feet. But when I land it's +\- 10 to 20 feet.
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Old Aug 12, 2012, 04:53 PM
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Originally Posted by Vlodek9 View Post
I do, prior to every flight. It does help a little and gets it +\- 2-5 feet. But when I land it's +\- 10 to 20 feet.
how many sats do you have when you take off and land? depending on the number of sats and where they are in the sky will affect the accuracy of the height reported on all gps systems. a number of satellites around the horizon are going to be able to triangulate your altitude allot more accurately than the same number of satellites directly above you. I hope this make sense
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Old Aug 12, 2012, 05:06 PM
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Yes it does. 90% of time I have 12. 10% I have 10. I'm going through my video to get a clip and post. Should be done in about an hour or two.
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Old Aug 12, 2012, 05:16 PM
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There's only been one flight where my GPS altitude was wrong by a significant amount. It was a 45 minute long distance high altitude flight, I imagine over the course of the flight I may have changed from sats on different locations that may have impacted the accuracy. I don't think I've ever had less than 8 sats ever. I noticed the error as I was descending for a landing as I had almost 80metres difference between GPS height and my barometric height. I chose to follow the baro as my guide as it was reporting me as lower. When I landed the baro was only 2metres out. I'd recommend it as an additional sensor as you can use it as a backup.
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Old Aug 12, 2012, 05:41 PM
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I think you may just have hit it on the head. When I get 10 sats, I show 12 by the time I land. So I think you are right and it could be the sat change that is screwing it up.
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Old Aug 12, 2012, 05:47 PM
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Originally Posted by Vlodek9 View Post
I think you may just have hit it on the head. When I get 10 sats, I show 12 by the time I land. So I think you are right and it could be the sat change that is screwing it up.
Generally waiting a few minutes for a good quality fix means you'll have no issues but as we both know you can still get inaccuracies. I find I get a fix very quickly but I power up and by the time I'm ready to fly and have done systems checks that by fix is as good as it well get. Buy the baro sensor, you won't be disappointed. Also the airspeed sensor is a must for me too
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Old Aug 12, 2012, 09:16 PM
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Chicago, IL USA
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I've given up on GPS altitude and just ordered the ET Microsensor V4 Altimeter. I actually don't have a real problem with the GPS altitude...I mean for leisure FPV who cares if sometime you're off 10ft or 20ft? But thought it would be fun to have a more accurate altitude...don't know what I'll really do with it though
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Old Aug 12, 2012, 09:45 PM
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Originally Posted by AdamChicago View Post
I've given up on GPS altitude and just ordered the ET Microsensor V4 Altimeter. I actually don't have a real problem with the GPS altitude...I mean for leisure FPV who cares if sometime you're off 10ft or 20ft? But thought it would be fun to have a more accurate altitude...don't know what I'll really do with it though
Agree 100%. But for me, I get a bit nervous trying to fly low (20 feet of the ground) because my depth perseption over a camera (via googles) is not that good yet. So I find myself relying on GPS altitude much more then I thought I would. But with sometimes +/- 20 feet well, you see my concern.
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Old Aug 12, 2012, 11:31 PM
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Ok, here is the flic of what I'm talking about in regards to GPS alt. The movie was a little longer then I originally wanted but I figure that more data is better. Please look at the alt latter on the right prior to take off and after landing.

MM GPS (4 min 14 sec)


I think this is a mute point now since I will be buying a baro and speed sensor.
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Old Aug 13, 2012, 09:23 AM
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Suomi, Espoo
Joined Sep 2011
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Hi,
Problem with RTH disengaging: During a quick scan of the forum I did not find a comment on this. I have a setup with eLogger v3, GPS v4, OSDpro and Guardian. Flight stabilization and heading hold work great. RTH also works using the test mode (3way switch).

I flew too far and RTH kicked in according to video recording, but since my failsafe also altered the 3-way switch, the menues came on, and since the RX lost/got/lost/got/lost contact, the settings for both Aux1 and Aux2 "oscillated" between two states in quick sequence, and ended up in starting the Servo Wizard (waiting to read the manual and click SELECT :-/). The text "RTH engaged" vanished during the menu flipping (video link stronger than 2.4G control link...) and after losing contact proper with RX (at ~90m elevation, with minimum RTH engage elevation set to 20m), the menu timed out, and I could watch the nicely stabilized and heading hold descent into the sea.

Failsafe programmed as 3ch on my electric training glider, and I checked that it kicked in on the ground before flight (I reprogrammed failsafes and run servo wizard just before, so I know).

Any hypothesis?
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Old Aug 13, 2012, 09:42 AM
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Austria / Vienna
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Originally Posted by Jstjern View Post
Hi,
Problem with RTH disengaging: During a quick scan of the forum I did not find a comment on this. I have a setup with eLogger v3, GPS v4, OSDpro and Guardian. Flight stabilization and heading hold work great. RTH also works using the test mode (3way switch).

I flew too far and RTH kicked in according to video recording, but since my failsafe also altered the 3-way switch, the menues came on, and since the RX lost/got/lost/got/lost contact, the settings for both Aux1 and Aux2 "oscillated" between two states in quick sequence, and ended up in starting the Servo Wizard (waiting to read the manual and click SELECT :-/). The text "RTH engaged" vanished during the menu flipping (video link stronger than 2.4G control link...) and after losing contact proper with RX (at ~90m elevation, with minimum RTH engage elevation set to 20m), the menu timed out, and I could watch the nicely stabilized and heading hold descent into the sea.

Failsafe programmed as 3ch on my electric training glider, and I checked that it kicked in on the ground before flight (I reprogrammed failsafes and run servo wizard just before, so I know).

Any hypothesis?
hi,

at first .. sorry for your crash, iīm hoping you recoverd the plane and the water doesnīt damage your electronics too much.

there are no hypothesis ... if the failsafe isnīt stored "correctly" it happens, like in your case, that the aux inputs switches into menumodus when the failsafe toggles the aux
next time you should program those channels to "neutral". also switch the aux-switches on the rc always back in their neutral position.
also use a switch on your rc and the "clarlyle-method" to make the rth switchable. as soon as you recognice the firtst failsafe-rth bring the switch to the rth position ... and give the rth enough time to bring the plane back in a position with better rc-reception.

cheers Thomas
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Old Aug 13, 2012, 11:58 AM
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USA, CA, San Diego
Joined Apr 2007
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Quote:
Originally Posted by AdamChicago View Post
I've given up on GPS altitude and just ordered the ET Microsensor V4 Altimeter. I actually don't have a real problem with the GPS altitude...I mean for leisure FPV who cares if sometime you're off 10ft or 20ft? But thought it would be fun to have a more accurate altitude...don't know what I'll really do with it though
Real airplanes, even the big ones, have the same problems with GPS. GPS altitude is just not as accurate as lat-long. And you can never get airspeed from GPS; only ground speed.
So pilots use pitot tube and barometric altitude. (Actually at low altitude AGL they use a radar altimeter also/instead.) If you want accuracy, you should too.
Of course barometric altitude is inaccurate when air pressure changes. But our flights are too short for that to matter, and we don't fly when storm fronts are going through.
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Old Aug 13, 2012, 12:11 PM
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Suomi, Espoo
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Quote:
Originally Posted by Thint1 View Post
hi,

at first .. sorry for your crash, iīm hoping you recoverd the plane and the water doesnīt damage your electronics too much.

As soon as you recognice the firtst failsafe-rth bring the switch to the rth position ... and give the rth enough time to bring the plane back in a position with better rc-reception.

cheers Thomas
Thanks Thomas,
Servos, Elogger, gps and diversity Multiplex rx fried (salt water). Osdpro, guardian, video tx and camera ok, as well as esc and batteries. Foam plane, so no prob with finding it floating - it stayed on course even after I lost video link, thanks guardian

There's no "neutral" on my rx; all 7 channels assume the FS state, whatever it is. As i have multiplexed aux2 with camera tilt, I am likely not to have time to bring it to "up" when losing the link.

The solution in my case seems to be that I save FS for Aux1 as 'test RTH' (up) as I use the 3pos switch for aux1. (imho this should be recommendef in the manual up front)

What I am still not sure of is under which conditions Rth disengages permanently even if FS is active (apart from flying below min rth altitude)
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Old Aug 13, 2012, 01:36 PM
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Joined Nov 2003
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Adam, thanks for the kind words! That's a great list (and others also), and I hope we can get most or all of those items in future.
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