SkyTraq has a different version of the 638 (not just different firmware) that emits corrections to the pps edge to go to 10nS, and after a lock it will work down to 1 satellite and maintain accurate pps. I don't know of any others that retain pps if they don't have a 3d lock. The antenna is important but it won't overcome an obscured view of the sky - at best you will get multipath or other errors with the weak signals. On May 1, 2012 11:33 PM, "Eric S. Raymond" wrote: > Dave Taht : > > I'm a little confused. > > > > There are two threads going by today. One is about a sirfIII and the > > other a ublox 6 > > > > I have been assuming they are one and the same, but perhaps I'm confused. > > You are. The first set of prototypes, from UniTraq, were SiRF-III + > CP2101. > These won't do - turns out the CP2101 driver can't wait on a handshake > state > change because the vendor never released enough programnming information. > > Gary is talking about the second set of prototypes, from NaviSys. > That's the uBlox + PL2303 device. It works. The next step is to > get them into volume production. > > > Secondly an item that has not been looked into much is the quality of > > the antennas, or the quality of the clock source when only a single > > sat is available.... > > Quality of antenna will matter for the device's ability to function in > weak-signal conditions, e.g. indoors. Clock time should be OK even with > a single sat - multiple birds are needed for the spherical trig to compute > position, but atomic time you get directly from each sat sample. > > > Thirdly, wow.... when can I get one of these puppies to play with? > > Gary has three. He's keeping one and sending me the second. Since OpenBSD > has no TICMIWAIT, Chris Kuethe is out of contention for the third and it > should logically go to you. > -- > Eric S. Raymond > _______________________________________________ > Thumbgps-devel mailing list > Thumbgps-devel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/thumbgps-devel >