Assisted GPS vs Sirf III?

[RobMob]

I am in the market for a pocket PC with built in GPS. I am weighing up the soon to be launched Eten x800 and the HTC TY-TN II. I understand the x800 will have Sirf III but no querty and the HTC will have querty but assisted GPS.

Can someone tell me which is better out of Assisted GPS and SIRF III. I know what SIRF III is but don't really understand much about Assisted GPS and whether it is superior or inferior to Sirf.

Many thanks

Rob

[mikealder]

Assisted GPS is where the device stores a small file containing the orbit positional data of the GPS Satellites, it is valid for 72 Hours, once it has expired you either connect the device to the PC for t to download the free update to cover the next 72 hours or use the on board phone to connect and download.
The data packets are very small, I find my HTC Artemis devices (which both use Assisted GPS) are extremely quick to acquire a positional fix, faster than my SiRF-III based units, other than time to fix AGPS doesn't do much else - Mike

[robertn]

You need to be in cellular coverage area for assited GPS to be of help - an overlooked issue for some people.

Assisted GPS sends you the data the GPS needs to aquire before it can get a fix. This data is sent from the cell site, which is close enough to you that it is useful. Without this data, the GPS looks for a satalite, then waits for the data to be sent. Once this is complete, it can then calculate a fix.

Essentially, the Assited GPS does a Hot Start each time you turn the GPS on.

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