question: does the lower signal also effect accuracy? On Wed, Jul 16, 2008 at 10:56 PM, Marcus Bauer <[EMAIL PROTECTED]> wrote: > On Wed, 2008-07-16 at 21:38 +0200, Alasal wrote: > >> What is the problem? >> - The Openmoko Freerunner have a long TTFF with the SD card in the >> phone. So it takes a long time (10min+) before you get your first GPS >> data. > > More specific: the GPS signal level drops by -20dBm, i.e. factor 100. > Signal strength of a GPS satellite above your head is around -127dBm. > Needed strength for a first fix is -145dBm with a minimum of three > satellites. Once the GPS chip has a fix, it can operate at signal levels > of -157dBm, thus making it possible to operate while there is data > transfer from/to the SD card. > > >> So if we have a first fix, the SD card isn't blocking the GPS anymore? >> - yes, the SD card isn't blocking the GPS if we have a first fix. >> (Some people even claim it's more stable) > > The FR's GPS performance is definitely top notch without the SD card. > > >> But we can't read of the SD card when the GPS is on? >> - Wrong, you will be able to read the SD card when the GPS is on. You >> will probably not be able to read the SD card when you're starting the >> GPS (appr. 30 sec), because the GPS will only block the SD card when >> it's searching it's first fix. After that you will be able to read the >> SD card again. > > You can always read the SD card. As said above the GPS signal > temporarily drops by -20dBm during i/o. > > The kernel patch is a pragmatic and well working solution and should not > effect daily use. > >> Summary of the summary: >> You will be able to use the SD card in the same time of the GPS except >> for the first appr 30 seconds. (And that's the worst case, because >> maybe Openmoko can find better hacks/fixes) > > With the help of AGPS you can shorten it probably to 15 seconds. > > > > > _______________________________________________ > Openmoko community mailing list > [email protected] > http://lists.openmoko.org/mailman/listinfo/community >
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