PEU said:
I have one doubt, The other day I was comparing my Garmin 48 gps (yes its old
) with the new ones sirf and no sirf enabled and one doubt came to mind:
Do the benefits of sirf technology are related to waas?
I mean after reading in the Garmin site that there are no waas stations in south america (I live in Argentina) I wondered if this affects somewhat the performance of the new sirf chips, and if yes, how it compares to the old 12 channels gps units.
Thanks
Pablo
With my module, I have utilities to turn off the WAAS and set up various things. I find the performance doesn't change much, with or without WAAS. I do see accuracy improvements when I enable WAAS.
The SiRF has the equivalent of over 200,000 correlators, instead of just 8, 12, or 13 (some of the current competing modern engines have a few hundred or thousand correlators) . This allows for it to look for matches in signals that would be considered un-useable in the older ones with only a few correlators. It also allows the unit to lock in sats much quicker.
If the software can handle it, the SiRF will act as a 20 channel GPS engine.
The SiRFIII adds special fast acquisition engines, satellite signal tracking engines, and multipath mitigation hardware.
The multipath mitigation helps alot in areas where the sattelite signals can be reflected, causing problems for previous generation engines.
The SiRFIII adds hardware which makes time to the first fix, very rapid, around 1 second from what I can tell. Even with weak signals to start with.
The SiRFIII also added extra sensitivity, as compared to previous generations, working with signals as low as -159 dBm.
The engine itself also supports EGNOS as well as WAAS.
Adding this stuff together, allows it to work well in foliage, urban canyons, and in many cases, indoors.
The engine is also fast enough to manage position updates at 10 times a second, unlike older engines that can only handle 1 a second. Though alot of software can't handle these rapid updates.
The engine itself uses very little power, once locked, and set for updates at once a second, it only consumes 75 mW.
There are various software modules that vendors can add internally to the engine, such as Foliage Lock and various other abilities.