Garmin Hotfix technology powered by Rx Networks GPStream SAGPS chipset

Newer Garmin Nuvi GPS including the 205, 205w, 255, 255w, 265T, 265WT, 275T, 500, 550, 750, 760, 770, 780, 755t, 765t, 775t, 785t, 850, 880, 5000, etc. have a new selling point of Hotfix technology.

Garmin Hotfix enable the GPS to be super fast within seconds in locating the satellites during startup. In fact, my Garmin Nuvi 255w can even work as if staying connected to satellites for a few minutes, when it started up indoor in the middle of my house.

This is made possible by using predictive calculations of satellite positions, which enables the behaviour of GPS satellites to be modelled based on broadcast ephemeris readings for accurate prediction of satellite positions up to a few days ahead. A single broadcast ephemeris reading allows the accurate prediction of satellite orbits which are developed and refined every time new broadcast ephemeris is obtained.

Some people are guessing that the Hotfix feature is based on SiRF InstantFix inside the newer version of SiRFstarIII chipset. However, we've just found out that Nuvi 255w is using STMicro Cartesio application processor instead, so it is not SiRF InstantFix which plays the magic.

In fact, the Garmin Hotfix technology is powered by Rx Networks GPStream SAGPS chipset. The GPStream Self Assisted GPS (SAGPS) is a derivative of GPStream Predicted GPS (PGPS) technology. GPStream PGPS is a 3rd generation Assisted GPS (AGPS) solution addressing the limitations of 1st and 2nd generation products, which is made available to some handphone devices with AGPS feature.

Click here to read more about Rx Networks GPStream SAGPS technology.

For those who are interested to know where I got the information about Garmin Nuvi 255w is using STMicro Cartesio application processor and Rx Networks GPStream SAGPS technology, it is mentioned in Page 10 of September 2008 edition (Volume 11 Issue 9) of Telecom Trends newsletter.