[Loadstone] SIRF3.2: disfunctional receiver?
monty at loadstone-gps.com
monty at loadstone-gps.com
Tue Feb 6 21:55:33 GMT 2007
In ultimate conditions a GPS receiver using the Sirf Star III chipset can
achieve accuracy of 10 feet (3 metres). By "ultimate conditions" I mean
your receiver must have a very good view of the sky, sky conditions are
clear, and you have a WAAS/EGNOS fix. Even without a WAAS/Egnos fix you
can achieve very good results. The best way to know what your GPS
receiver is capable of is to read it's technicle specifications. In my
experience most say that you can expect an accuracy of between 10 metres
and 15 metres. (aprox 34 - 50 feet) It is often better than this but
that might be the worst case scenario.
So, lets say you save a point when your conditions are poor and your GPS
reciever has an accuracy of 10 metres. Lets also say that unluckally,your
GPS receiver thinks it is 10 metres to the left of where you are at
present. Later, when you try and find the spot again, you are faced with
equally poor conditions though this time your GPS receiver thinks it is 10
metres to the right. This effectively would mean that you are 20 metres
from your saved position. In an absolute worst case scenario using the
technical specifications of 15 metres accuracy, the above example could
potentially turn into 30 metres.
Having said all of that most of the time it is considerably better but
like everything else in this world, there are a lot of variables so
results can and do vary.
As far as saving points while on the move that might not be a bad idea.
Why don't you experiment and report your findings to the list.
The "GPS Accuracy" function in Loadstone is simply reporting the value
your GPS receiver is sending to your phone. The lower the number the
better. This value is based on things such as satelites in view Etc.
It would seam that every GPS manufacturor handles the GPS commands a bit
differently. The ones that seam to work across the board are the
Cold/Warm/Hot resets but the WAAS/EGNOS, and Power-Saving functions really
are hit and miss. GPS receivers do not acknowledge weather the command
worked or not nor do they report the current state. This is why you have
On/Off settings both available to you. This sucks but that is something
we just godda live with!
I personally found and I think others would agree, once you use Loadstone
for a while and get to know the capabilities and behaviour of your GPS
receiver things do get much better. Plus, we are attempting to make
improvements to Loadstone all the time!
On Tue, 6 Feb 2007, R. Neill Hadder wrote:
> Hi Monty and all,
> Thanks for the feedback. "10 to 20 meters is pretty good" -- Really? I was
> thinking 10 feet or so. Were my expectations for GPS just way too high,
> then? I'd appreciate confirmation of this fact so I can stop scowling and
> cursing at the GPS receiver--which, since it resides in my pants pocket,
> makes for some odd looks in public as well as from my dog. Since "maximum
> approach" defaults to 10m, it seems like less than 10m accuracy is what
> you're used to, no? Also, I now really don't understand what the "accuracy"
> figure means if it isn't a reflection of correlating my position to the
> coordinates of a way point.
> To answer your question, these are points I've entered myself. One idea
> that came to me is that I'm entering point data while standing still and
> thus subject to drift, so I wonder if I'd get better results by entering
> points while walking. For example, hit pound sign, then stop, then use
> "from commencement." I already have static threshhold at 2.
> On the connection issue, my phone is a 6682. I suspect the power saving
> mode was on. I'll see on the way home.That might account for connection
> problems as well as lack of signal, which is really suspiciously tenuous. I
> hope there's a way to eventually place a tick or dynamically update the menu
> regarding power save state, since on my menu both options are always there
> and I don't know if it's on or off, or really what is happening, if
> anything, when I enter certain commands. I suppose that depends on whether
> the receiver delivers feedback, of course.
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> Loadstone at loadstone-gps.com
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