This may be stating the obvious, but it tripped me up when I was trying out my Garmin Etrex. You have to be still in order to get a fix. I had the Garmin attached to my bicycle and I was riding up and down my driveway while waiting to go off and map the neighborhood. No fix until I *stopped* for a minute or so.
Peter On Sun, May 16, 2010 at 8:42 PM, David Rysdam <da...@rysdam.org> wrote: > On 05/13/2010 08:19 AM, David Rysdam wrote: >> On 05/12/2010 06:13 PM, Joshua Judson Rosen wrote: >>> Cold tests >>> >>> were performed when both Pocket PC and GPS receiver were >>> powered off (if GPS receiver has a separate power source, the >>> GPS receiver was unplugged) for a period of between 8 to 12 >>> hours requiring a cold start. >>> >>> Warm tests >>> >>> Warm tests were performed when both Pocket PC and GPS >>> receiver were powered off (if GPS receiver has a separate >>> power source, the GPS receiver was unplugged) for a period >>> of 30 minutes >>> >>> Hot tests >>> >>> Hot tests were performed when both Pocket PC and GPS >>> receiver were powered off (if GPS receiver has a separate >>> power source, the GPS receiver was unplugged) for a period >>> of 15 minutes >> >> You missed the colder-than-cold test: >> - >> Factory is where the receiver has no knowledge whatsoever of Almanac >> data in turn to locate the satellites and retrieve Ephemeris data, and >> for a full Almanac to be downloaded can take approx 12.5 mins, hence >> most companies suggest a factory start of 15 minutes. >> - >> >> So we already know the N810 has to be worse than it should be, due to >> multiple reports even on this list of >15 minute TsTFF. >> >> Also, I apparently "cold test" my dedicated GPS 1-2 times per day. It's >> always read to be a GPS before I'm ready to be a driver. Perhaps that >> says more about how long it takes me to start driving than about how >> fast my GPS is. >> >> That said, I'll try to test it. I'll assume the N810 needs a factory >> start by this point and then start doing some cold timings. Assuming it >> doesn't take so long that I have to terminate the test. > > OK, so my tests are complete. I controlled the GPS with MaemoMapper, > which shows how many satellites you've heard from (I guess) and what the > signal strengths are. > > I'm basing average performance on these tests: > http://www.pocketgpsworld.com/ttffcomparisons.php > > 1) Until Saturday, I hadn't had a fix for many months, so I was going to > count that as a "factory" start. Factory start allows for around 12-15 > minutes. I got a fix in under 4 minutes. Then I realized that although > I was outside, I was still WiFi'd in to the house so it was using AGPS. > Result: Invalid. > > 2) A little over an hour later, I tried from a WiFi-free location. > 60-90 minutes is more than 30 minutes (warm test) but much less than > 8-12 hours (cold test). According to the baseline, cold tests should > take ~1 m, warm tests ~30s. N810? 5 minutes. > > 3) As soon as I had a fix for a few seconds, I disconnected and retried. > This would be a hot test and should take under 10-20 seconds. N810? 5 > minutes *again*. > > 4) Over 12 hours after that, I disabled WiFi at home and tried again. > This should be a strict cold test and again should take 1 minute. N810? > 13 minutes. > > Furthermore, I think it would have taken longer if I'd had more > patience. It went from 0-5 satellites (I thought 4 or 5 was enough, but > it didn't complete then), then wandered down to 1, then back up to 5. > This was at the 12 minute mark. So I pointed it up at the sky (it had > been resting on the ground) and suddenly all the signal strengths leapt > up and I got a fix within a minute after that. > > Conclusion: The N810 GPS hardware and/or software definitively sucks. > _______________________________________________ > gnhlug-discuss mailing list > gnhlug-discuss@mail.gnhlug.org > http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/ > _______________________________________________ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/