sears at cs.berkeley.edu
Sun Jul 13 12:48:14 CEST 2008
Yes, there is still hope.
The current software drivers do not save any state between GPS locks, so
the GPS device is needlessly re-downloading information from the
satellites each time it turns on. Downloading the data seems to require
a much better/more consistent signal than calculating the phone's
It sounds like a (partial?) fix is in the works. There were some links
to scripts posted to this mailing list a few days ago, but they came
with copyright restrictions that prevent redistribution...
My phone sometimes takes 10 minutes to get a fix, but can track its
current position from a car seat (not just near the window), and indoors
in my pocket. It's good enough for in-car navigation, and for use as a
speedometer, though with a couple of seconds delay added in. Also, I
see a few meters of jitter when the device is not moving.
After losing signal in a tunnel for 15-30 seconds, it restored its fix
immediately after I left the tunnel.
Not counting the time to get the initial lock, this behavior is better
than what I've seen from some inexpensive name brand gps devices,
suggesting the antenna is "good enough", assuming saving and restoring
the chip's state works.
Yorick Moko wrote:
> Is there still hope this is not a hardware bug?
> On Sat, Jul 12, 2008 at 10:59 PM, Jim Morris <ml at e4net.com> wrote:
>> Jonathan Spooner wrote:
>>> I've been playing with my GPS and finally got a fix using agps diag
>>> tool. I stood the gta02 up on my garden table using a pop bottle :-) I
>>> think bottom line the gta02 has a poor antenna.... in fact the first
>>> time I got a fix I did so at the point I rested my free stylus on top of
>>> the gta02!
>>> Once I had a fix I used the signal strength screen in the agps diag tool
>>> and its then plain to see the signal is precarious at best with an
>>> average strength of around 28 which is greatly affected by orientation
>>> and nearby objects from hands, stylus, people etc pretty much what you'd
>>> expect in a device thats receiving a very weak signal.... except we know
>>> the say system is working so that only leaves the gta02 internal antenna
>>> as the problem.
>> I found exactly the same thing, the unit has to be stationary for a while,
>> you need to swizzle it
>> around its vertical axis until you get the maximum signal strength, and
>> then leave it for 10 mins to
>> get a fix. It must not be touched or moved during that time.
>> It is pretty impractical for a mobile device though to do that.
>> Lets hope some of the techniques to preload data will help this.
>> Jim Morris, http://blog.wolfman.com
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>> community at lists.openmoko.org
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