GPS: Why it sometimes takes ages to get a 3D lock

[@charlesjones5070]

Lee nice job on summarising the key take-aways here. My day job involves lots of work with GPS receivers, and it gets very complex very fast. HDOP and VDOP quality is a direct function of what position the satellites are at in the sky that the receiver is choosing to use. If they are all low to the Horizon, you get poor HDOP, but better VDOP The explanation I use for the non-engineers for Hot/Warm/Cold start is: Hot = valid time, position, Almanac and Ephemeris data is present. Typically less than 10s for first fix Warm = valid time, position and Almanac is present. Between 30s and 2mins is typical for time to first fix Cold = No valid Almanac is available Can take up to 12.5mins, but typically in the order of 5-8mins for first fix For rules of thumb - Almanac data (coarse orbit of satellites) is valid for about 5 months, it takes a long time to get from the satellites directly as every satellite broadcasts almanac data for all satellites in the constellation. Ephemeris data (precise orbit data) is good for only 4 hours. Each satellites transmits it's own Ephemeris data

[@Painless360]

Thanks Charles. It can be easy to get into too much detail with most of the topics in the hobby when making a video aimed at newcomers to the topic. Thanks for posting! :D

[@christianmarkussen6412]

One trick that I use is to power the GPS from a pad on the FC that is powered when the USB cable is connected. This way you can power the aircraft with a power bank or similar and let it get a lock. When you do this then the VTX is unpowered which also helps to get a quicker lock and also avoids overheating the VTX. Once you have a lock then plug in the battery, disconnect the USB and go fly😎

[@returntohomefpv3232]

INAV has a system to put your vtx in low power mode until you arm, then it sets it to the power level you preset

[@Painless360]

Not with DJI it doesn't :D Happy flying!

[@returntohomefpv3232]

@@Painless360 True! I guess I'm still in the dark ages with my analogue lol. Didn't know that, thanks.

[@eddie_Za]

Question, after that flight, u unplug the battery, do u need to redo the process? Or the gps it set for that place.

[@christianmarkussen6412]

@@eddie_Za Once you have got a GPS lock and the GPS has downloaded the satellite almanac (list of which satellites are available) then the next GPS lock (same day) will be much quicker. Attaching the battery bank will still help but the difference will be less.

[@michaelreyes5]

Problem solved, moved my 1.3ghz vtx away from gps and now gps work great.. thanks lee.

[@adamsfpv4924]

Good info! Always wondered why after burning one pack, My quad would lock as soon as I powered up and armed the quad.

[@ApappieK]

Thanks for the info. On my good old Dart I suddenly had to wait 10 minutes before getting a GPS lock with only 6 satellites. Then I realised I rerouted my Frsky receiver antennas close to the GPS. And since the RX is sending the telemetry data to my TX, I created a lot of interference close to the GPS. Rerouting again the RX antennas to the underside of the Dart, improved waiting times to get a GPS lock and I'm getting over 20 satellites again.

[@pixelcomet]

Tip1: Shield the GPS wires with foil from a coax cable, then wrap them in tape for insulation (clear tape looks cool, ISS style) Tip2: Use a solo 5V BEC with XT60 and USB socket to power the GPS (over the FC) and wait for the 1st lock (in this way the VTX stays off while waiting)

[@audiogek]

Tip: Put the gps on top of the lipo with velcro. Lipo shields most of the emf.

[@ales94x]

No damage on hard landings?

[@audiogek]

@@ales94x I don't really freestyle with the gps quads so they don't do hard landings. But the few times I did crash while flying through trees it survived and was still on top of the lipo.

[@skvaderfpv]

Ran into this problem yesterday. Locks might be slow, but that slow was unusual. The weather was somewhat overcast. And after 5 minutes plugged in no fix. After taking off, I could get max 4 satellites. Thanks for your explanation.

[@herramakkara3712]

Distance to other electronics makes all the difference in the world in my planes. Same tiny gps receiver takes ages to lock when installed to 5” quad and find only 7 sats. In fpv wing the same unit finds 20 sats in couple of minutes. I’ve noticed matek voltage regulator especially problematic and need to give more distance to it.

[@jamesemery1]

I unplug the vtx (so its doesn't over heat) and let it sit and pick up the 3d lock or I use a1 cell lipo to power the gps only. good info as always Lee stay safe.

[@SkyHorseTech]

Great video as always. Another limitation is that most of the UAS GNSS systems are single band (Here+, etc) which take longer to obtain a fix. Switching over to a multi-band GNSS such as uBlox' ZED-F9P you can obtain a cold start fix in less than a minute (datasheet says 24 sec). A bit more $ but higher accuracy. Thanks!

[@ChrisBalmforth]

Interesting video Lee, once again I learned something!

[@MCsCreations]

Really fantastic info, Lee! 😃 Thanks a lot!!! Stay safe there with your family! 🖖😊

[@SummerCrowfpv]

Great video I feel like I’m always fighting to get a good gps lock Thanks for all the information it gave me a few ideas to improve my system 👍🏻

[@NATGEOANDSTUFFPaulbrannan]

Great info as allways Lee thankyou.

[@karthikharirp7299]

Hey... Your videos are perfect in all situations.... 1st comment for this video 👍

[@agrxdrowflow958]

Brilliant!

[@ellingolsen3194]

Here's my story: I discovered that if I removed power from the VTX then I would easily get 11 satellites within 3 minutes. With the VTX powered up it would never get there. Someone said I needed a better GPS and, admittedly, the one I had was cheap. Instead, I replaced my crappy HGLRC VTX with a Rush Tank Mini. Happy, happy.

[@Painless360]

Sometimes devices produce unexpected frequencies in the range that the GPS uses. A perfect example of what I was talking about. Thanks for posting.. Happy flying

[@madforit9661]

Just bought a Foxeer 120 GPS with the New M10 Q Chip, 25 minutes later, NOT locking but still showing available satellites, any ideas Cheers

[@Painless360]

It could be interference... Best of luck

[@pablofpv]

Next video, try a comparison of a FC with a GPS running Betaflight and then INav. See which gets the fastest lock?

[@AdroitConceptions]

The GPS lock is 100% part of the GPS module, so the FC firmware shouldn't matter at all.

[@saifcathum3423]

Very interesting. How much interference can heavy snow cause? I had issues in winter with autonomous flight on an INAV quadcopter.

[@Painless360]

Not sure but humidity will affect the signal..

[@ales94x]

You can power up GPS by connecting FC to USB. I just use my phone

[@Painless360]

Not always. Some flight controllers don't pass the 5v to the GPS. Happy flying!

[@michaelsanderssa]

So probably a stupid question. Why do we not have these issues with the mobile phone. They seam to lock onto sats quickly.

[@Painless360]

Because the phones download the GPS positions using their data connection from the carrier so they have a 'warm' or 'hot start' every time.

[@breakflight]

Also, phones are always on, so you don't get GPS Cold Start or even GPS Hot Start, you get GPS already on.

[@tracibeacer670]

I can get 20 sats no problem but I don't seem to get a lock , no compass no gps modes . Do you think it's a faulty unit?

[@Painless360]

Maybe or a problem with the setup in the flight controller configuration. With 6 or more sats. most systems will have a good enough 3D lock.. best of luck

[@karthikharirp7299]

One of my Wi-Fi (2.4GHz) telemetry (Pixhack fmv3, CUAV PW-LINK) frequently get disconnect and reconnect with my host(laptop- intel dual band wi-fi, smart phone). Any solution to fix it ? Thank you in advance.

[@Painless360]

Could be lots of things. What troubleshooting have you already done?

[@karthikharirp7299]

@@Painless360 sorry for the long delay, soon I will share the details with your via Email.

[@BrunO-qt6vf]

first flight...i switch off dji vtx next flights the gps finds the satellites faster. Thanks for the tips

[@Painless360]

Me too. Happy flying!

[@sleepingbearffg5008]

Let me guess?? It's made in China? Lucky don't have to re solder. Lol great vid and information 👊👊💪💪