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GPS on an airliner - difficulty getting a satellite fix
PetalumaLoco
I flew from SFO to Spokane last week, and took the Aspire One netbook with Microsoft Streets and Trips 2008 along. The GPS worked fine on the way up, it was cool seeing
568MPH
33,128FT
on the GPS pane .

Looking out the plane window and seeing exactly where we were on the map was interesting and educational. I had driven the same route a few times, good to see what the terrain looked like from the air.

However, the trip back didn't go so slick with the GPS. I never could get it to hook up. It did display "Receiving Data", but I never got a track on the map or speed, altitude, lat&long, etc.

Any ideas? I rebooted the netbook, restarted S&T numerous times and unplugged/plugged the GPS. Usually that does the trick if it's being recalcitrant, but no go. Works fine on the ground here now.
tcassidy
Getting a satellite lock to start with is the trick. Obtaining lock under adverse conditions (speed and minimal view of the sky) is much more difficult than maintaining it once you have it.

Terry
PetalumaLoco
Tanks Terry. On the way north I had a western sky. I sat in the same seat on the way back and had an eastern sky. Guess the sats weren't in the right place for the return trip.
SpadesFlush
Maybe get your initial position lock before you takeoff while stationary then put on standby until you are underway.
PetalumaLoco
Quote:
Originally Posted by SpadesFlush
Maybe get your initial position lock before you takeoff while stationary then put on standby until you are underway.
You mean close the netbook, but not shut it off? Will it maintain a lock that way?
tcassidy
As long as power is available to the USB GPS, it should maintain lock.

Terry
SpadesFlush
Quote:
Originally Posted by PetalumaLoco
You mean close the netbook, but not shut it off? Will it maintain a lock that way?
Well, I don't know about your specific hardware, but I know that I can put my Viliv S5 UMPC on standby after I get a satellite lock and it will resume after a few seconds when I bring it out of standby without going through all the start-up folderol. In this way, I get my initial satellite lock before I get in the car and start out and then just come out of standby when I start driving. I have not tried it in a plane, though.

If your hardware O/S is Windows, there should be a standby power option.
PetalumaLoco
Looks like that may work. I fired it up and got a lock here at home, then let it hibernate, wake up and I had to check Start GPS Tracking again, but it did resume tracking.

I'll try it next time I'm in that situation.

Thanks
d111
If you are using a consumer grade GPS that is not made for aircraft use, the internal microcontroller does not process the data fast enough.

Get yourself an aviation grade GPS and your problems are solved.

They are equipped with much faster and better data processing capabilities.
PetalumaLoco
Quote:
Originally Posted by d111
If you are using a consumer grade GPS that is not made for aircraft use, the internal microcontroller does not process the data fast enough.

Get yourself an aviation grade GPS and your problems are solved.

They are equipped with much faster and better data processing capabilities.
Thanks for the tip. I did this just for entertainment. Nice to know another reason I was having trouble.
SpadesFlush
PetalumaLoca, take a look at post #22 of http://www.laptopgpsworld.com/1111-streets-trips-library-member-trips for what someone has done for fun with GPS in an airplane.
d111
Here is a directory of Aviation Grade GPS and updated prices as of April 2008....

Note the $$$

http://www.aopa.org/pilot/gps.html

http://www.aopa.org/pilot/handheldGPS.pdf

Aviation GPS : Radioworld

Basically, general aviation GPS are good to something like Mach 1.

The cheapest handheld unit will probably run you $500 and probably is only certified for speeds up to 200 knots.

If you want real military grade GPS that is good above that speed, be prepared to pay plenty.

Just in case you want to have a GPS on a JDAM kit....
SpadesFlush
Further, if you don't have S&T, see the attached screen shots from Nelson's map.
Attached Images
09-08-06.jpg   09-08-06-2-.jpg  
d111
Many moons ago, using Microsoft Street and Trips 2002 or thereabouts with a cheap Garmin GPS (the yellow one that took 4 AAA batteries)....

The GPS / Software combo was so slow that I would drive past a road before the GPS conclude that I am "there".

Can't imagine how it must be like using a non-Aviation grade GPS on a plane moving at 400knots.

I hope you are not flying KAL 007 or its modern equivalent.
tcassidy
That would have been a Delorme single channel GPS receiver. It took about 3-4 minutes from start to lock in good conditions and could lose lock in moderate foliage. You were probably using a Delorme navigation program as S&T didn't do GPS in those days.

Consumer GPS are 1000% more sensitive these days and will often work fine in the adverse conditions presented by a passenger aircraft.

Terry
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