Great 'Sat Nav' Hunt (merged)

shohaib

is TTFF chip any good

tdodd

TTFF means Time To First Fix - in other words, how long it takes to get an accurate position after you've turned it on. It is not a type of chip. It is a measurement of performance applicable to all types of chip.

The TTFF can vary for each unit depending on whether you moved position since you turned it off. If you haven't moved then TTFF should be fairly quick - a few seconds or certainly less than a minute. But if you've moved position (I don't know by how much the movement needs to be) or if the signal was lost before you stopped moving, it can take much longer to get a first fix. The Navman PDA/GPS units say it can take up to 20 minutes to get a FF the first time they are used although in practice probably a lot less - it does depend on satellite signal strength.

I'm no expert in all this - I only got my GPS last month so I'm just quoting the stuff I've read on GPSPASSION and POCKETGPS websites and forums. As I've said before, my SiRFSTAR III based Holux GPSlim236 works very well and this is borne out in the test results I mentioned in post 494.

shohaib

im new to gps so thanks for all the information, Sirf III how many satellites has it got and whats the best amount of channels you need for in car sat nav on mobile

tdodd

The Holux GPSlim236 has 20 channels and I guess it would be the same for any other SiRF III unit but I'm not certain. In any case, as I said in an earlier post, there are only 24 satellites up there and some will be completely invisible because the earth gets in the way so 20 channels is more than enough. Furthermore, you only NEED 3 good signals to establish your position for motoring, walking, skiing or anything else on the ground. More satellites gives slightly more assured accuracy and a safety net in case one or more satellites vanish from view (say a building gets in the way in a city for example). 5 or 6 good signals is plenty for reliable motoring but you need at least 3 at all times in order to keep a fix.

gwentvillan

what are the differences apart form price ?

Interested in getting one of these ASAP

kirkie_2

gwentvillan wrote:

what are the differences apart form price ?

Interested in getting one of these ASAP

Have a look here

gwentvillan

thanks.

can some point me in the right direction - there are two sites that list the availability and price of tomtom systems but I forgot to bookmark them :-( any ideas what they are ?

eileenfromplaistow

Garmin i3 at our Asda now £148

kirkie_2

eileenfromplaistow wrote:

Garmin i3 at our Asda now £148

Are these as good as the Tom Tom One?

welche2

garmin 13 only £99 at kwicksave/somerfield