A quick fix indeed

by Volker Weber

tomtom720

The TomTom I started testing this week is different from all other devices I ever tried in one important aspect: within seconds it knows its position. If you ever tried a personal navigation system before, you know that it can last a few frustrating minutes until you get your first GPS fix. The reason is that the device has to fetch the GPS almanach from a known satellite. Since the satellites send this almanach only every 30 seconds, and the transmission must not be interrupted, it can take quite a while until the device can read the full almanach without being interrupted. This of course works better if you do not move in the meantime.

As it turns out, all recent TomTom devices — GO (720/520/910/710/510) und ONE (XL/New Edition) — have a feature called QuickGPSfix. What it basically does is to download the GPS almanach into the device either through your PC/Mac or via your mobile phone. And that means, you can have a fix in seconds instead of minutes. Since the almanach needs to be updated every couple of days, you either have to pair your mobile phone to give your device internet access, or you need to dock the device with an internet connected PC/Mac at least once a week.

Comments

Interesting, I experienced this slow GPS fix problem when I borred a Garmin device in the US. I'd never used a stand-alone sat nav before.

I've had sat nav in my Lexus for many years now and it's always known where it was before I left the driveway. Why can't a Tom Tom do this?

Do Lexus leave the receiver powered up?

Ben Rose, 2007-09-27

A Lexus is somewhat heavier than a personal navigation device and has a larger battery. So it cannot be carried around as easily to different places, and it also does not need to be switched off completely. And you have the ability to measure distances travelled by counting how often each of the wheels is turned.

Volker Weber, 2007-09-27

Isn't this called aGPS?
(more detailed in German)

Florian Steinel, 2007-09-27

No. A-GPS tries to solve the same problem, but with a different solution.

Volker Weber, 2007-09-27

Ben,

The reason the Lexus sat nav doesn't have the problem is because it has dead-reckoning so once it gets its very first fix it always knows where it is because it tracks your speed and steering.

Ed Saipetch, 2007-09-30

Volker,

My Lexus has a very big battery, it will drive for 15-20mins without using any petrol :O)

Ben Rose, 2007-10-03

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