GPS reception - GNSS only?

[znww5]

Just been reading around the VK172 u-blox GPS specification.  It would appear that the '172 only seems capable of receiving either GNSS (the American GPS constellation) or the Russian Glonass system, but not both simultaneously.

I wonder if anybody can confirm that the either/or situation is true and whether anyone has experimented with 'dual' GPS dongles. I have a GPS160 unit which supports GNSS and Glonass simultaneously, but only over a bluetooth connection. I'm assuming that PA is only interested in an NMEA stream on its USB port so any dual system GPS should work provided you have the driver and the dongle isn't too power hungry.

Has anyone experimented along these lines?

[JCurtis]

I plugged the PAW supplied U-Blox 7 dongle into the u-Box development toolset (I have a GPS development toolset here, long story) and I could not set it to GLONASS at all, it would just revert back to GPS.  However it was receiving EGNOS though.

Watching the config commands it receives and acknowledges them, but doesn't act on them.  I tried to update the FW to uBlox7 1.01 from the v1.00 it says it has installed, it failed to detect the internal flash.  So I tried to ask the chip for it's OTP uBlox security ID programmed as it leaves the factory, I get blank back, so I suspect it's a fake chipset in the dongle, not a surprise given the cost of them.

Although another U-Blox M8N receiver I have here is doing a sterling job of getting hold of GPS, GLONASS, and Gallieo with EGNOS support too.

[exfirepro]

Hi Jeremy,

Very interesting! Don't suppose you have an example of the 'alternative' PAW VK-162 GPS mouse available? Would be interested to know if it performs any better. Certainly seems to do so from my own empirical evidence, but that could just be down to better positioning.

Regards

Peter

[znww5]

Ah - that's interesting. I was going to download the u-blox software and have a poke about, but my anti-virus program flagged up a Trojan warning, so I was going to give it a go on my 'testing' laptop later today.

It would be interesting to know from the tech guys if there is a GPS driver library loaded onto the RPi, so other dongles can be used or whether they just loaded the u-blox-specific driver. I have established that the RPi will work with a FlightAware dedicated 1090MHz SDR dongle, so maybe we have the library for GPS dongles too.

I also need to test if the orientation of the supplied dongle affects reception. The u-blox patch antenna is on the black-printed side (uppermost when plugged into the RPi) of the unit and I know that my XGPS160 definitely does not like trying to 'see' through the PCB and battery. It might be worth mentioning this to those users who remotely mount the GPS dongle.

Part of my 'wishlist' would be support for dual GNSS/Glonass GPS dongles - and a bluetooth option for wireless GPS units.

Regards,

David

[JCurtis]

Hi Jeremy,

Very interesting! Don't suppose you have an example of the 'alternative' PAW VK-162 GPS mouse available? Would be interested to know if it performs any better. Certainly seems to do so from my own empirical evidence, but that could just be down to better positioning.

Regards

Peter

Nope, I don't have one of those knocking around.  I did see the dongle has a small battery inside, no doubt to keep almanac data for faster starts.  I wonder if this dies what impact it has, it should just be a longer initial acquisition time, but who knows.  I might pop it off the board and see what happens at some point... 

[JCurtis]

Ah - that's interesting. I was going to download the u-blox software and have a poke about, but my anti-virus program flagged up a Trojan warning, so I was going to give it a go on my 'testing' laptop later today.

It would be interesting to know from the tech guys if there is a GPS driver library loaded onto the RPi, so other dongles can be used or whether they just loaded the u-blox-specific driver. I have established that the RPi will work with a FlightAware dedicated 1090MHz SDR dongle, so maybe we have the library for GPS dongles too.

I also need to test if the orientation of the supplied dongle affects reception. The u-blox patch antenna is on the black-printed side (uppermost when plugged into the RPi) of the unit and I know that my XGPS160 definitely does not like trying to 'see' through the PCB and battery. It might be worth mentioning this to those users who remotely mount the GPS dongle.

Part of my 'wishlist' would be support for dual GNSS/Glonass GPS dongles - and a bluetooth option for wireless GPS units.

Regards,

David

The dongle, in effect, can be just a serial port to the device streaming NEMA messages. If you have one, give it a try.

[Paul_Sengupta]

I have established that the RPi will work with a FlightAware dedicated 1090MHz SDR dongle

I think this uses the same chipset as the PAW one though.

Is there any particular reason you want GLONASS?

[znww5]

Hi Paul,

Just upping the chances of maintaining a successful lock and memories of GNSS prediction graphs which gave low sat counts.

Nice to see you on here BTW - escaping from the flying forums for a touch of sanity perhaps?  ;-)


David

[Paul_Sengupta]

Sanity? Me? 

I can't say I've had any problems with loss of GPS reception, but I have a canopy aeroplane so a fairly clear view of the sky from my dashboard.

[znww5]

I fly a Piper letterbox, so could do with a few extra sats! I have a WAAS EGNOS capable GNSS & Glonass bluetooth GPS (Dual XGPS160) which I'd love to use, but I have no idea how I could interface it with the PA unit. 

[Paul_Sengupta]

I wouldn't worry about it, when you're in the air the supplied GPS does a good job. If you have the unit on your dashboard, you'll be picking up more satellites than you'll ever need. The supplied one is WAAS/EGNOS.