Just a thought. I've installed miniGPS on my 7650. If we could know from our operator the location of every cell in a map, we could get our position in the map, right?
GPRS Possibilities
Yes, but it would be really rough position, depending on how many cells there are.
At best something like 400m radius.
If the MiniGPS would get info of all the neighboring cells and compute from that it would be much more accurate. 😃
It is unlikely that an operator would want to give out precise information on the location of its transmitters.
If you had the location and signal strength of one transmitter you could work out your approximate position as a circle around the centre of the cell - good approximation as the further you are away the weaker the signal.
If you had the proximity to two cells based on location and signal strength of both you could calculate your position to one of two locations (one if you were in a direct line between them - getter approximation as the circle around the cells would intersect in two places.
If you have three reference points (locations) and distances (signal strength) you can pinpoint, approximately, a precise location. This is still not perfect as the signal strength would vary due to all sorts of factors not just distance (weather, altitude, transmitter faults, etc.).
Even saying this you could probably make an accurate location to within 10 - 20 metres or so.
I hope this is useful.
8)
If we know accurately where we are (with 3 references positions), can we translate that into lat/lon cordinates? I guess we still need to know from our operators where are these transmitters.
Exactly, unless the transmitters send out Lat and Lon info, which I doubt they do (but could if they wanted I suspect).
The operators may be able to produce their own software to perform this kind of service i.e. triangulate your possition, or they could approximate it by advertising in the cell broadcast a place name for the transmitter and hence we could get a reading such as "500m from St Pauls" or "1Km from Newport Pagnall Services"!!!
Bob
😃
I may be wrong, but I think across the whole of Europe, all the operators do indeed "triangulate", (at least in Spain) and then they can respond to automated questions such as "nearest chemist" etc. Because of privacy issues (did you tell your wife you are working late, so why are you in a football stadium???) the individual can subscribe to it (default = no) if he wants to.
This has big possibilities in business software for vehicle fleet positioning etc
Paul
Check out this site:
http://www.sitefinder.radio.gov.uk/
You can find out where your nearest radio mast is, and find out it's cell ID. I asked the people involved if I could have a copy of this database, and get this... they told me it's "commercially sensitive" and they're not allowed to let the public see it! MAybe someone should tell them their web site is probably not the best place to keep sensitive information... 😊