Dutch wrote:AFAIK most if not all Sirf based GPS units have a messagerate of 1 hz (once pr. second) in NMEA mode. And we all know that the faster we go, the fewer AP we'll probably find. If we say that the max speed we use when wardriving is app. 50 Km/h that update rate would mean we would move 13,8 meters between each position update.
Do we need more precision than that ?
I think you just made the point why we need more position fixes. It is accepted practice (never tested to my knowledge) that 30 mph. That means you are moving .5 miles in one minute. Keeping in mind that consumer GPS accuracy (+-15 meters) is based on fixes acquired from a fixed position, I guestimate that moving adds about 10-15 meters of error to the position fix. So the more position fixes you have, the more accurately you can locate AP's.
As Lincomatic correctly say, by using Sirf binary, we suddenly move the Lat/Lon format calculation of the position from the GPS to the computer.
Instead of just parsing the clear text output of the GGA or GGL NMEA messages, NS have to parse the binary data AND calculate the Lat/Lon from X/Y/Z coordinates.
I think this is incorrect, the position fixes are still calculated by the receiver's firmware. You are just moving parsing the binary stream to the program.
Is that worth it to get positionupdates every half second meaning our max moved distance is now 6,9 meters at the 50 Km/h speed ?
This really depends on what you want the tool to do. If you are using it for "fox and hound" type location in a moving vehicle then maybe. For general purposes I don't think its necessary to have sub-second position fixes. Then again, I like having as much data as I possibly can get, but that's just me.
Personally, I think XML output is a more important feature than supporting binary GPS formats.