[Loadstone] Direction fix mode

Stephen Bennett sbennett at rnzfb.org.nz
Mon Dec 3 00:31:12 GMT 2007


Hi All

Perhaps an off-shoot of this is the idea that we could eliminate
multi-path by taking readings of the traveller's direction and screening
out any that are just way off beam. Does this sound feasible?

For example, if I've been going north or thereabouts for ten seconds
then southwest for two seconds then north again for ten seconds the
system could safely decide that the southwest was a multi-path and could
be ignored.

All the best

Stephen


-----Original Message-----
From: loadstone-bounces at loadstone-gps.com
[mailto:loadstone-bounces at loadstone-gps.com] On Behalf Of Shawn
Kirkpatrick
Sent: Monday, 3 December 2007 1:19 p.m.
To: loadstone at loadstone-gps.com
Subject: Re: [Loadstone] Direction fix mode


After giving this some more thought I think what we're talking about is 
reinventing static navigation mode. The problem is like this: assume a
walking speed of 4 kilometers per hour, that translates to just 
over 1 meter per second. Unfortunately that value is well within the
drift 
for most receivers. Trying to compensate for that would mean knocking
out 
speeds below the drift range and that would be pretty much all walking 
speeds. Waiting until a certain distance had gone passed might work but 
would result in intermitant speed readings. You'd only get a reading
when 
the distance had been met and then it would drop back to 0 until the
next 
calculation. If we assume that on a good day the receiver's drift radius
is 
8 meters then that means you'd only get a speed reading every 8 seconds,
the 
rest of the time it would be 0. That's not a good situation at all. I
think we'll have to see the results of software heading and speed 
calculations before we can think of how to fix the drift problem. There 
probably just isn't a good way around this, if the receiver's sending
bad 
position data then there's no accurate way of correcting it.

On Sun, 2 Dec 2007, Jurgen wrote:

>> The biggest
>> problem I can see with this would be a slow response
>> at low speeds.
>
> Thats the point! A slow responce that is useful is much beter then a 
> useles fast one.
>
> And the ones who want to have the fast useles function, can set the 
> value to zerro - and gon!
>
> There is a possibility to find a better way, but it is combined with 
> collecting positions in a circle buffer with variable size. And I 
> think, it is much to complicated for this problem
>
> And for Your argument, that GPSReceivers would have this ...
>
> for the first, GPS for walkers still is not the main market. And there

> is a big problem for the producers of receivers. Thay have to be 
> compatible to NMEA standard to fid then neets of the market and to 
> feed LS ;-). So they can only support, what NMEA can transport. there 
> is no NMEA data set, that can communicate, how the direction is 
> calculated. It's  the same problem as the one, that we don't get 
> information about battery status. deo You think, this is because  it 
> is so complicated to calculate battery status?
>
> J.
>
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