I have been playing around with a BlueNext BN-909GR which has the SirfStar III GPS chip. The chip and implementation by BlueNext was amazing. I was able to get a lock of up 10 satellites on a clear bright day when the receiver was placed indoors! I was going around the house and it kept a lock on at least 1 satellite 90% of the time and it switched to DGPS when it didn’t.
When it was sitting next to me on the computer about 1.5 – 2 meters away from a glass window it had 9 satellites locked. I clenched my hand around the unit and it dropped to 5 satellites. It was impressive. Usually on a cold start it took around 1 – 2 minute to get a lock but normally it will get one faster. This was without the Assisted GPS (AGPS) aid although the chip does support it. I think the chip gets a better signal than my aging TomTom Go700.
The SirfStar III uses the NEMA 0183 standard which is the format for the GPS data from the unit. It is a string containing a series of data separated by commas. Each data is in a certain order and different standard have different data and in different order. This has posed many issues with JavaME which I will discuss in another post.