The LD-3W bluetooth GPS is listed under accessories for the N810.

Is this a mistake, or could you really have two GPS devices available?

It's a shame the range of bluetooth is so limited. Differential GPS is very accurate if the data is processed properly. With two GPSs, the n810 could be an electronic tape measure or a device to help you find your car in a car park. How much of a killer app would that be?

Ooo, nice idea, dormant! I don't have an answer but it *looks* possible...

I'm not sure I follow.. Differential GPS isn't two GPS receivers, it's a concept of one GPS receiver plus a correction factor sent (by radio, for example) from a fixed-point location which _also_ has a GPS receiver and can (because it's in a fixed, well-known location) calculate an adjustment factor that can be transmitted to you.

Nokia is not an original manufacturer of GPS units as only manufacturers of GPS chips can be considered as original manufacturers of GPS units.
So a range of GPS devices available for use with Nokia 770/800/810 is in no way limited.
Any bluetooth GPS unit can be applied.
Don't expect Nokia to offer full range of GPS units.
Nokia stays for cell phones not GPS units or GPS technology.

Neverthless I have developed algorithm and posted request to Nokia maemo developers to introduce two GPSs operation in N810 and in other models to have better quality GPS data and better GPS signal received for processing to avoid and limit signal lost or no GPS fix problem.

If you are a developer and can write a code I can provide you with more details on how to implement that feature called 2 GPSs navigation operation.

Darius

Bum, I thought I'd deleted this thread, not posted it.

TA-t3: There are two different types of differential GPS. Most people recognise the type you mention. But you can buy commercial surveying equipment that achieves much greater accuracy by using two or more GPS receivers and processing the data from them together - either in real time over a radio link to a computer or in post-processing. Accuracy can be less than a centimetre (I am a volcanologist and we use this type of GPS data to measure deformation of volcanoes.)

"Proper" differential GPS won't work on something like the N810. Commercial units use the L2 frequency (no, I don't know what it is either) and information that isn't available in NMEA sentences.

So I think all could be done is just differencing the two GPS measurements. I haven't tested this, but it might give accuracy of about 1m under the right conditions. Good enough to find a car, but you'd have to be within 10m for the bluetooth to work anyway.

Another idea for greatness dead in the water.

Darius2006, I am not a coder. I can script, but the last programming I did was in FORTRAN, in the days when it was in capital letters. The n800 might just get me back into coding - I am tempted to do something based on gps-saver.

Oh yeah then it could be used on missiles!
Great idea!

What are you talking about?

GPS has been used in cruise missiles since the mid 90s. Bombs really don't need any great accuracy.

For anyone reading this thread out of interest, I should clarify that the type of differential GPS I was talking about has a relative accuracy of less than a centimetre. The absolute accuracy is much larger, and depends on how long you record data for and how it is processed, but is probably a few metres.

So you can tell how far apart two things are, and the direction between them, with much greater accuracy than the actual position of either of them.

Awesome app! This really doesn't need 2 GPS receivers unless your car moves while it's at the car park. Simply record the location of the car as you leave it, then display it on a satellite image of the car park. Add your current location and you shouldn't "loose" your car ever again!

Admittedly, I don't have the very best of GPS receivers, but if I take it off the top of the dash next to the windshield and place it where my N800 rests against the face of my speedometer (don't worry, it only blocks < 25 mph and > 80 mph), I can't get a GPS fix. If the N810 doesn't have an external GPS antenna, is it going to be useful? Do other GPS units (i.e. Garman, etc) have external antennas?