USB-GPS Working in PilotAware

[Admin]

Don't Panic !

This is not as bad as you are thinking, and is also a pretty complex situation.

So firstly some background.
In the initial version of PilotAware I use Location Services (via CollisionAware) to get my position.
The Location Services data may be supplied by WiFi data, Cellular Data, internal GPS or
an external BT GPS - the source of this info is under the control of iOS.
Location services is a 'high level' API, which insulates the programmer from worrying about
things such as 'quality of fix', '2D/3D fix', 'number of satellites in view' etc.
The location information is used internally by PilotAware in order to calculate relative distance &
height from other traffic.

The Navigation tools, SkyDemon, RunwayHD, EasyVFR, Air Navigation Pro - all work differently
when communicating to a traffic device such as PilotAware or Flarm, let me describe how they
get their information when connected to PilotAware

SkyDemon:
Uses Position Data from PilotAware
Uses Traffic Data from PilotAware

RunwayHD:
Uses Position Data from Location Services
Uses Traffic Data from PilotAware

EasyVFR, AirNavigation Pro
Uses Position Data from - Configurable
Uses Traffic Data from PilotAware

So in order to provide Position Data to SkyDemon (and others) I have to convert the Location
Services data back into a set of NMEA sentences.
This is in effect 'faking the data', and in so doing, because I am insulated from the low level
details, I simply have to say 'Fix data is OK', '3D fix' '5 Satellites in view', because in reality,
Location services has already determined this for me.

Now the important Part !

In the initial implementation of the GPS integration, I ignored the fix/quality data being supplied
by the GPS device, and simply fed back the data to whichever tool was using this data,
(in reality only SkyDemon), which explains what you are seeing. The GPS is telling me the data is
bad, but I fake it and say the data is good and passit on.

THIS IS WRONG, but was done for expediency to simply prove the interface was this working.

What needs to happen is either
1. Pass the data along with the fix/quality information
2. Filter the data based upon the fix/quality information

I have not yet decided which is the best approach, I am guessing SkyDemon will ignore the
GPS data if the fix/quality indicates it is poor, but maybe I should make that decision internally.

Thx
Lee

[Admin]

OK, I'm less than happy with the U-Blox7 GPS module I have - it has 'crashed' (i.e., stopped getting a fix) 4 times now this afternoon, green light stopped flashing and putting me at 0:0 lat/long (North Pole!) - it will re-acquire and start working on a reboot of the PilotAware box so it's def. not the fact that it's lost sky view, but can take an age on a power-off restart.

Considering it's supposed to be both GPS and GLONASS, it's a bit of a PoS really and not as reliable as the in-built GPS in the iPad or my Bad Elf Pro+

Follow up question on my last posting.
By any chance were you running CollisionAware AND an external GPS, or just the external GPS ?
Thx
Lee

[trapdoor]

Hi Lee,

All understood. But that doesn't get past the fact that my GPS dongle appears to be unreliable in keeping a fix. It's currently sitting in full view of the sky, by a window overlooking the Bristol Channel, with NO goo fix - no green flashing LED, nada. It will come back (maybe) for a period, and then drop out again.

Both my iPad and my Bad Elf have a good fix, my Bad Elf is reporting currently a lock with 24 birds (both GPS and GLONASS) and most of those are showing 80% or greater signal strength.

So either there is something awry with my module, or they just aren't up to much. It just seems odd that rebooting the device gets it working again - for perhaps 10 minutes, then it start dropping out again.

I don't have a PC to plug it into to monitor it's sky view.

Oh, in answer to your last question, no. Not running any other app just using the external GPS....

[Admin]

BTW regarding the usb/gps, you can quite happily hot plug this device.
It will recognise removal and  re-insertion.
Would be interesting to see if this re-awakes the gps

[falcoguy]

I am thinking of looking at this.

Do you think the following might work - the aerial can be better positioned than having USB on board - I will eventually hide the unit away.

http://www.ebay.co.uk/itm/USB-GPS-RECIEVER-FOR-LAPTOP-ANDROID-LATEST-UBLOX7-CHIP-FAST-WAT-PROOF-2-MTR-LEAD-/291555386081?hash=item43e20e22e1

or will only the dongle labelling RasPi work?

Dave T

[Admin]

I am thinking of looking at this.

Do you think the following might work - the aerial can be better positioned than having USB on board - I will eventually hide the unit away.

http://www.ebay.co.uk/itm/USB-GPS-RECIEVER-FOR-LAPTOP-ANDROID-LATEST-UBLOX7-CHIP-FAST-WAT-PROOF-2-MTR-LEAD-/291555386081?hash=item43e20e22e1

or will only the dongle labelling RasPi work?

Dave T

Hi Dave,

I have the same thing coming on a slow boat from china, from here
http://www.aliexpress.com/item/VK-162-GPS-engine-board-Module-with-Antenna-USB-G-Mouse/32439292777.html
So have not had time yet to try.
I think somebody else reported using this on the forum ....
Thx
Lee

[Richard]

So either there is something awry with my module, or they just aren't up to much. It just seems odd that rebooting the device gets it working again - for perhaps 10 minutes, then it start dropping out again.

Trapdoor,
    I have the same problem, The GPS arrived today and on trying it drops as you have described.  There seems to be some work to do here to get it working. I will try a moving test later but i expect the same problem.

Any Ideas Lee?

[Admin]

So either there is something awry with my module, or they just aren't up to much. It just seems odd that rebooting the device gets it working again - for perhaps 10 minutes, then it start dropping out again.

Trapdoor,
    I have the same problem, The GPS arrived today and on trying it drops as you have described.  There seems to be some work to do here to get it working. I will try a moving test later but i expect the same problem.

Any Ideas Lee?

Hi Richard,
Are you saying you do not get a green pulsing led ?
Also can you confirm you have it plugged into the correct USB port (it is currently hardwired) ?

also how long were you running ?
the time to first fix can be upto 15 minutes
https://en.wikipedia.org/wiki/Time_to_first_fix

There is nothing really to be done in the software to be honest other than read from the device
Thx
Lee

[Richard]

Lee,
   I will do some more testing. Yes green light flashing OK no problems there. It just supplys North 00.00000 South 00.0000 in sky demon. It worked OK for about 1 min.

I'm Not running ColisionAware App.
 Mobile data turned off also same thing with mobile data turned on in the IPad.
Using latest release

I will try some moving tests later on to see if the problem is still there.

Everything connects OK as far as I can see. The numbers in the web interface for the GPS keep changing as it re-fresh is this correct?

[trapdoor]

I find:

• Cold start takes an age - like it's not stored the almanac or is taking an age to read the ephemeris data.
• When it does lock, it positions correctly, BUT I am finding that it's positional accuracy isn't great so you get spurious G/S or Hdg indications
• It drops out of lock frequently - green LED will stop flashing whilst it's out of lock BUT it can drop out and back in quite quickly (or that may just be invalid GPS data)
• GPS has a great sky view from a window but moving back even a small amount (or even closing the curtains) appears to make the lock loss issue much worse

I'm not convinced the quality of these cheap dongles is up to much. It's possible some may be OK but I'm sure I have a dud or suspect one. Compared to my Bad Elf Pro+ which is also GPS/GLONASS this thing is junk. OK, the Bad Elf is 40 times more expensive ... so no comparison really I suppose.

[ianfallon]

Still waiting for my "piece of junk" to arrive! 

[Richard]

ok, It may not be too bad after all......

Just been testing again.  This time put it in the middle of the garden while I set in the house where it is warmer..... About 6m away through the window.

OK ran SD on its own with cellular data off on the Ipad (So it will not use the internal GPS)
Also Not running the Collision Aware app.

It was left running for over 1 hour (while monitoring) No drop outs of any kind from the GPS
No Connection dropouts from any where 
Received ADS-B Traffic from over 100 miles away (Approx.)

Tried the smaller ADS-B Areal recommended in one of the threads..... Traffic was intermittent and kept disappearing and re appearing at different intervals. OK I know its not tuned to the correct frequency. I feel it is not good enough for use, though it does tidy up the PilotAware device, That's just my choice.

The next step is to try it in the air. (It will soon be summer )

[trapdoor]

Which antenna are you using for the ADS-B one? You can't use the small helical that is meant for the ARF module but I get excellent results with a decent Siretta Delta2C antenna which is meant for Cellular (it's almost the correct frequency and better tuned than the one that comes with the DVB-T module) - http://www.ebay.co.uk/itm/361362426353

I get traffic out to the South East of Ireland using that antenna and I'm on the Bristol Channel coast   

[Richard]

Trapdoor,
    I'm using the same as you.... The one you recommended in the ebay link.
Its strange that I get intermittent reception from the small antenna but fantastic reception from the original supplied antenna.  I have altered the the original by shortening the wire and removing the magnet in the base then stuck it to the box. This may have helped with reception with the shorter coax cable.

[trapdoor]

How are you connecting the 2C antenna to the module?

I'm currently connected using an MCX to SMA pigtail as the MCX to SMA straight adapter + antenna wasn't 'strong' enough directly into the module.