SiRF V's NMEA

pletharoe · Occasional Visitor Joined: Jan 19, 2005 Posts: 13

Hi all,
What's the difference / pros & cons of SiRF and NMEA?

Pocketgps · Posted: Mon Jan 24, 2005 4:08 pm Post subject:

hello pletharoe

SiRF is the new boy on the block, NMEA is the acquired standard and one used by 95% of GPS applications. Why a standard ? NMEA is getting old, it was designed to talk at 4800 baud (4kbps). Modem speeds today are 56kbps so you can see NMEA is slow. SiRF has brought about that change by increasing speeds and utilising full serial speeds up to 115200kbps. The thing is although NMEA is slow, some GPS Receivers will work at higher than 4800, but this is what NMEA prefers. The amount of GPS data sent down the serial port is very small and can easily be transmitted in 4800 baud so although you could reach higher speeds, there isn't really any necessary to do so. SiRF uses higher speeds because it can transmit the data quickly and put the processor into a wait state which in theory means it utilises less power, newer SiRF chipsets like SiRF IIe also have low power consumption which help even further with sustaining power to the GPS Receiver.

Regards

PocketGps

pletharoe · Occasional Visitor Joined: Jan 19, 2005 Posts: 13

Thanks

ckuethe · Posted: Thu Feb 03, 2005 9:31 pm Post subject:

The SiRF protocol is also far richer. It can express many varied quantities about the internal state of the receiver, signal quality, precise time, constellation status, and allows you to exert far more control over the hardware... NMEA has its place as a no-nonsense protocol for providing simple PVT information. For some of us that's not good enough. To put it in perspective, when I turn on all the debugging on my receiver, I easily sustain 24kbps out of the receiver. I'd imagine it only gets noisier if SiRFDRive were in use.
_________________
http://www.ualberta.ca/~ckuethe/gps/

	PocketGPS
	Web