Bluetooth GPS and Speed problem

[bohpilot]

I have a Ipaq 6365 and a Ambicom BT112A-GPS.

It works on a Fokker 100 with the Ambicom positioned at the read window.

Strangely though above 150knts the position fails, but still shows satelites available.

I have tried it with Tomtom 5 and Memory-MAP using the CAA maps and still get the same problem.

Do you think its the Bluetooth Unit of my Ipaq 6365 that is causing the problem

[Complex_Type]

The spec for that GPS receiver says it works up to 515 metres/second (1000 knots) so I wonder if the Ipaq can't process the information quick enough to keep up with the changing position. Try it with a different PDA.

[bohpilot]

Thanks for the fast reply, i was wondering if it is the IPAQ that is the culprit, it has the Texas Instruments OMAP 1510 processor 200 MHz.

I do have problems with other programs, its just interesting that it happens about the same spped with two different programs.

[Dehavillanddriver]

I have a different bluetooth GPS and an IPAQ and it doesn't work when the 737 is in the air.

Works fine when taxying - been too busy to notice at other times!

My GPS also says that it has a high GS capability but I hadn't thought that the IPAQ may have been the problem, but it makes sense now.

The GPS says that it is seeing the sats OK, but not tracking them....

[Superpilot]

A very common issue. Seen this with the unbranded bluetooth GPS's sold on eBay in the past. Where did you get yours? I use the Emtac Crux II (http://www.emtac.com/products/bluetooth/). Cost nearly 40% more than the ones sold on eBay. I've tested mine as a passenger on a Dornier 328 (high wing!), and after the initial difficulty of aquiring the satellites my GPS was coping with over 350KTS!

First thing to remember is this has nothing to do with the power of your IPaq's processor speed. The vast majority of GPS units output a GPS sentence known as the $GPRMC sentence. E.g:

$GPRMC,092204.999,A,4250.5589,S,14718.5084,E,350.00,89.68,21 1200,,*25

This contains the speed at which you are travelling at. Therefore the speed is calculated by the GPS and not your IPaq. The other thing to bare in mind is that just because you are travelling faster does not mean there is more data to process - it's actually the same. Your GPS probably returns a new fix every 1 second, it does this when stationary and when going along at 150KTS (as long as the right number of satellites have been aquired).

Thus the culprit is probably the GPS device (not able to aquire a fix at speed). You can probably prove this if you connect your IPaq up to MS Flight Sim 2004 (http://www.homepages.mcb.net/bones/04fs/tutorial/GPS.htm) :cool: (with FS acting as the GPS device). You'll see your IPaq can cope with speeds over 700KTS

[bohpilot]

Solved the problem, I purchased a new GPS a Holux Bluetooth GPSlim 236.

This unit is fantastic, I was getting 7 satellites inside the cabin with the unit in my shirt pocket. It never dropped its position.