TTFF

GuyC · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

As many negatives have been posted I would like to point out a positive for TTN2. I find that the time to first fix and recovery after losing coverage e.g. in a tunnel is a vast improvement on TTN1.

I use a Navman 3000 on an IPAQ3630, with TTN1 it would take 2-3 mins to bring up a position with 0 speed and then immediately go back to searching, it would do this 2-3 times before getting a good lock. With TTN2 it gets a lock within a minute if I turn it on where I finished my last journey. If I turn it on after I have set off it takes a little longer but does not do the cycling between position and searching which it did within TTN1.

Stillo · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

You'te very lucky it takes me atleast 8 mins to get a fix , there must be something wrong with mine.

Cheers Stillo

SJTaylor · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

I've noticed that TTFF is slower with TTN2 and my Socket BT. Doing exactly the same thing, just sitting in my driveway next to the road, it's taking a hell of a lot longer. I notice on GPS status that there are plenty of good strong sat signals but they are greyed out whereas in TTN1 they'd be red almost immediately.

aero · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

I've noticed that if my BT GPS has a fix, then start TTN2, it loses it's fix for a minute or so.

I've no experience of any other software, so I'm not sure what to expect.

JackT · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

I have observed the same : the TTN2 GPS application reinitialize the BT GPS at startup : any previous fix is lost...

After one test, it seems that choosing "NMEA" (or "SIRF" is the unit is in SIRF mode) instead of "Emtac Wireless GPS" avoid this reinitialization...To be confirmed.

JT

RichardS · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

I have also noted this with the Emtac BTGPS. You switch on the Emtac, and it often gets a fix within seconds (green LED flashing), yet at the exact instant you launch TTN2 the green LED immediately goes to solid and it has to re-acquire the fix, often taking longer than the fix when the Emtac was first switched on. I try to avoid this by first launching TTN2, and then afterwards establishing the BT connection.

However, apart from this start-up issue, the unit seems to re-acquire fix (eg after a tunnel) quite quickly.

I have already mentioned this to TomTom support (albeit at the same time as complaining of crashing). But of course there has been no acknowledgement.

Richard

aero · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

Because my current set-up works so well, I'm going to accept this for the time being as a minor gripe. It'll be interesting if there is a benefit with a different driver. Let us know JT? Thanks.

Dave · Posted: Sun Sep 14, 2003 8:04 am Post subject: TTFF

TTFF's are really a fine art. Pick a number, got it ? Now pick another number, got that ? now pick another number ? They're all different, one is 30 sec, second is 1m 04s, third is 42s.

Most of TTFF (and I hate to say this) is down to luck. Downloading the Ephemeris data takes 30 secs, if you're at the right place at the right time, then you may get a 30 sec cold fix. If a bird flies out from a nearby tree, a branch sways in the wind, anything like this in the vacinity of the line of sight of the receiver can cause a delayed fix. Now sometimes there's enough data to get a 2D or 3D fix, but it's taken 42s, sometimes there's no where near enough data and you have to start the 30sec cycle off again.

Software can also cause a problem, ever had the Pocket PC lock for a second or two ? Unfortunately you don't know whether it's an interface lock (eg you can't pull down the start menu by tapping it), or if it's a physical lock which could have just lost a segment of data it was receiving.

Our TTFF's do vary on the equipment we test, and we have to be practical with it, and take a whole host of TTFF's then an average, and that's what we publish. It really is a fine art, and what you may be experiencing is a software go slow/lock up problem, or an external problem which is halting the data stream from being complete.

	PocketGPS
	Web