What is required for GPS Lock?

[Jubalr]

So yesterday I was in a bad area for GPS and surrounded by very tall trees all around me. Was going to fly manual anyway but waited 3 minutes to see what GPS did. To my surprise, I got a lock and ready to Fly indication. Looked at what I had for satellites and it was 6 with an HDOP of 2.4. I thought I heard that the requirements were for more satellites and lower HDOP, but just found this on the 3DR site..

The following requirements define a GPS lock: Reported horizontal position accuracy < 16 ft. (5 m) Reported speed accuracy < 2 mph (1 m/s) Number of satellites ≥ 6 Difference between GPS and inertial navigation vertical velocity < 2 mph (1 m/s).

 

[Microsprint]

do not take off if you have 6 or 7 sat ....it is worth waiting for more ...trust me ...even if it says ready for take off ...if you take off and it loses sat. RTH might not work

 

[Jubalr]

do not take off if you have 6 or 7 sat ....it is worth waiting for more ...trust me ...even if it says ready for take off ...if you take off and it loses sat. RTH might not work

Yep, been there done that. Been using Pixhawk for awhile. The 'lock' is only meeting a accuracy minimum. I have been in areas where I had to take off with 5-6 sats and get the rest while above obstructions. Only difference is the accuracy of the home point may be 50' instead of 3. But it will at least get you close enough to retrieve if necessary.

 

[Operator74656]

I frequently fly manually into gps denied areas and I got to wondering.....
What happens to RTH position if you lose gps while in the air and then reacquire? Is RTH reset or does solo remember the initial takeoff fix?

 

[rrmccabe]

No gps is set when you power up motors. If you lose gps and it comes back it still knows home.

I am surprised manual allows you to fly into no fly zones. Even in manual gps is still active.

Dji locks you out in atti mode.

 

[prowler9]

So I take off with 7 sat all the time. Once in the air I get them really fast. Should I wait till I get more ?

Sent from my SM-N910V using Tapatalk

 

[Microsprint]

RRMCCABE is correct ...if you take off with gps locked it should remember Home point ...But I had lock took off ..lost signal ..got back signal ...then lost it again when trying to land ..Solo landed then wanted too take back off...have to remember to keep stick in down position (left stick) till motors shut off

 

[Microsprint]

Its funny when I bought my Solo did update ..went out and flew NOT ONE PROBLEM sat were 13 everytime.Flew 7 or 8 missions ...then did new update and bam got 5 or 6 sometimes 7 it took a long time to get 10 or 13 ...So now I just wait ...$ 1000.00 buck I can wait to be sure ..Also when changing battery shut everything down and restart all ...It take about 5 mins sometime..

 

[aggravated...]

Its funny when I bought my Solo did update ..went out and flew NOT ONE PROBLEM sat were 13 everytime.Flew 7 or 8 missions ...then did new update and bam got 5 or 6 sometimes 7 it took a long time to get 10 or 13 ...So now I just wait ...$ 1000.00 buck I can wait to be sure ..Also when changing battery shut everything down and restart all ...It take about 5 mins sometime..

My 2nd Solo came with the updates preinstalled and I have been flying it everywhere for the last 3 weeks. It was locking on within a minute or two every flight.

Last Thursday I want to test the follow me mode so I updated the Solo app. Since then I'm having to wait LONG periods of time to get it locked and at times having to resort to calibrating it to get it locked.

Not sure how the app could have caused this but that is the only thing that has changed. I did replace a wifi router but it is not the interference because I went up on the hill some 1500' from my house wifi and it still did not lock quickly as it had been.

Anyone else have this experience after updating their Android app? Also where is the HDOP info/data located? In the app or controller?

 

[Cynthia Farr]

do not take off if you have 6 or 7 sat ....it is worth waiting for more ...trust me ...even if it says ready for take off ...if you take off and it loses sat. RTH might not work

this happened today the RTH button did not work lost GPS I have done the cardboard modification I wonder should I take this cardboard out

 

[tomnjfl]

No gps is set when you power up motors. If you lose gps and it comes back it still knows home.

I am surprised manual allows you to fly into no fly zones. Even in manual gps is still active.

Dji locks you out in atti mode.

According the the Solo App, I'm in a no-fly zone every single time I fly, but I've never had an issue. It always lets me fly.

I wasn't even aware that Solo would restrict your flight. I thought it was up to you.

 

[SARDG]

According the the Solo App, I'm in a no-fly zone every single time I fly, but I've never had an issue. It always lets me fly.

I wasn't even aware that Solo would restrict your flight. I thought it was up to you.

I can say with a great deal of certainty that Solo will NOT restrict your flight in no-fly zones.

 

[PdxSteve]

If DJI made a car it's throttle wouldn't go above 65mph/the speed limit. They don't believe in allowing you to make your own decisions. They just make them for you.

3DR expects you to use your brain, common sense and follow the law with using your own free will.

 

[SARDG]

...3DR expects you to use your brain, common sense and follow the law with using your own free will.

Can I get an "Amen"?

 

[Rusty Jones]

I am going to go out on a limb here and say the Pixhawk 2, as produced by 3DR, has a design/build issue. There have been many reports of people with wobbling Solos. Where it would fly fine, then suddenly tip over a few degrees then correct it's self, drifting, etc. And most/all were fixed when the Pixhawk 2 was replaced. As it is now, my Solo requires frequent level calibration, and if I run "Auto Analyze" in Mission planner I often get IMU mismatch "warnings" It seems one of the IMUs is not happy. I think it is temperature dependent. I can take my Solo out of my cold car (good AC ) and the first flight, in 80° weather, will have these mismatch issues. Subsequent flights seem more stable, leading me to believe the Solo needs to warm up. I have not done any "back to back" testing on this as I am packing to move to a new Condo.

@fpvsteve On those logs that have high 'Z' vibrations, could you run the log through Mission Planner's Auto Analyze feature and see what it reports about the IMUs?

 

[fpvsteve]

@fpvsteve On those logs that have high 'Z' vibrations, could you run the log through Mission Planner's Auto Analyze feature and see what it reports about the IMUs?

IMUs are all OK.
My further analysis shows that the vibrations are a subsequent result of the erratic drifting, not the root cause.
Again, a level calibration fixed it as I can confirm after further 3 days of flying.

 

[erikgraham]

So yesterday I was in a bad area for GPS and surrounded by very tall trees all around me. Was going to fly manual anyway but waited 3 minutes to see what GPS did. To my surprise, I got a lock and ready to Fly indication. Looked at what I had for satellites and it was 6 with an HDOP of 2.4. I thought I heard that the requirements were for more satellites and lower HDOP, but just found this on the 3DR site..

The following requirements define a GPS lock: Reported horizontal position accuracy < 16 ft. (5 m) Reported speed accuracy < 2 mph (1 m/s) Number of satellites ≥ 6 Difference between GPS and inertial navigation vertical velocity < 2 mph (1 m/s).

There's always been something a little screwy with HDOP in arducopter. For a long time it was really using PDOP, but I thought that was fixed last summer or spring. Can't remember when. Then I think there was (still is?) an issue where it was hardcoded and changing the Param GPS_HDOP_GOOD had no effect. I *think* it was locked at 2.5

In any case, 2.5 should be the default value so at 2.4 you were good to go, assuming all the other checks passed.

 

[Jubalr]

There's always been something a little screwy with HDOP in arducopter. For a long time it was really using PDOP, but I thought that was fixed last summer or spring. Can't remember when. Then I think there was (still is?) an issue where it was hardcoded and changing the Param GPS_HDOP_GOOD had no effect. I *think* it was locked at 2.5

In any case, 2.5 should be the default value so at 2.4 you were good to go, assuming all the other checks passed.

Hi Erik, I read that quote and couldn't remember it. But then I saw the date; July, 2015! No wonder I didn't remember. Yes, I believe that the GPS lock requirements have been tweaked with just about every update. I know there is also a timing parameter that is (was) very important.

 

[PdxSteve]

Innn fact, they just changed it again this afternoon in the 3drobotics/ardupilot-solo branch today here: GPS check improvements by priseborough · Pull Request #227 · 3drobotics/ardupilot-solo · GitHub

Fix bug in GPs driver HDoP reporting
Make GPS checks adjustable
Log GPS check results to dataflash
relaxing the requirment on HDOP for arming

 

[Bigskyflyer]

If DJI made a car it's throttle wouldn't go above 65mph/the speed limit. They don't believe in allowing you to make your own decisions. They just make them for you.

3DR expects you to use your brain, common sense and follow the law with using your own free will.

I hear what you are saying, but living in a society where everyone wants to sue the manufacturers because they do something stupid, maybe dji is covering their butts. Could you imagine what would happen if some dumb ass flying a phantom or solo or any drone took out an airplane because he decided to fly over the 400' limit or fly too close to an airport? They would go after all parties involved. I have no problem with a limit of 400' AGL. It just isn't worth the risk. But there are plenty of idiots that do it all the time. It is just a matter of time before all drones are required to have these limitations. Just look at what they have done to cars over the years, seat belts, airbags, speed limiters, etc. Hell even most cars have a black box in them now that records everything you do behind the wheel. Sorry for the rant but we live in a day and age where a lot of people refuse to take personal responsibility for anything. Very sad indeed.