Hi, On Sat, 03 Jan 2009 13:50:18 +0100 Fox Mulder <quakem...@gmx.net> wrote:
> Since a few weeks i'm using fso-gpsd without any big problems so far. > The only problem is that the TTFF (time to first fix) is always >1 > minute and sometimes it needs quite a lot of time. The only solution > for me to be sure to get a fix within <30 sec is to use the agps tool > which downloads the almanac and ephemeris from ublox for my region. yes, I tried integrating hot-start into ogpsd, but somehow I had problems with supplying ephemeris. Just some days ago I noticed something that made me think the culprit is still the time calculation. The SVs that zhone claimed were visible suddenly made a jolt and were positioned differently. It was more than one, so it wasn't just one almanac that got updated. I'm not completely sure, though, didn't look too closely. > The problem is, that the gps chip doesn't have any internal memory why > it needs to download all relevant gps data every time it is powered > up. So i thought if it is possible to save the relevant gps data > before shutting down the gps which can be done by fso-gpsd or kernel > automatically. Than after starting the gps fso-gpsd/kernel feeds back > the data to speed up the TTFF. This would be the same way most gps > receivers work. It actually does have memory, but lacks a backup battery which is supposed to power the memory of the GPS while main power is off. ogpsd already stores and restores almanac, GPS/UTC timeoffset and approximate last position. It's not restoring ephemeris because I had weird problems with that (TTFF increased to several minutes). > Maybe this is already implemented somewhere but i don't think so > because the TTFF without agps is always quite slow. Some things are there, some are missing. At the moment I'm busy getting SMS stable so I wont have too much time for GPS in the near future. Regards, Daniel Willmann
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