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Mon Aug 14 00:15:05 BST 2006


Nax search radius = When you use a function that requires Loadstone GPS to 
determine the location of a Point, it searches for the nearest point using
a vectored search pattern. It begins searching with a rather narrow radius 
and progressively widens the search field until it finds a point. The 
maximum search radius value determines how far (in kilometres) Loadstone GPS
will  search until it stops. At the moment there is not a method of stopping 
the  search while in progress so it is advised to keep the value as small as
possible  without compromising usefulness.

What is likely happening here is you you only have a couple of points in 
your database and if you search in a direction where there aren't anymore 
points it will keep searching until it rounds the globe and approaches 
your other point from the other side.  To help this you should use a much 
smaller value in the Max Search Radius setting.  If you only have a couple 
of points you could even set it as low as 10KM or something like that and 
it will be quite quick.  I have lots of points and find that 200KM meets 
my needs very well.

Another thing to note in the test you performed is that the points you 
created are very close together.  Most GPS receivers have a best accuracy 
of 3-5 metres  so it's quite possible that even though you walked 5 metres 
down the platform that both of your created points  could be much closer 
together (even right on top of each other in theory)!  Remember when you 
create a point the actual physical coordinates of that point could be 
anywhere in the accuracy radius (3-5 metres) in any direction.

I suspect the other thing that might have happened is that the Last 
Position recorded  by Loadstone prior to disconnecting the GPS will not be 
identical to the second point you created.  This is because All SiRF3 GPS 
receivers have a bit of drift when standing still.

In general what you should expect from GPS technology when thinking in 
terms of train platforms is that if you are lucky and created a well 
positioned point you should be able to know what platform  you come in on 
the next time you enter the station and if you create multiple points you 
should perhaps be able to identify the top and the bottom of the platform 
but probably nothing like being able  to identify each train car or 
anything like that!

Please let me know if you require further clarification and keep us posted 
on your progress!

Best Regards,
   Monty

  On Tue, 15 Aug 2006, 
Brett wrote:

> Hi all,
>
> I don't yet have a bluetooth GPS receiver, but am intending to get one.
>
> Anyway, I met up with a friend of mine at the train station on the way
> home from work, he has a bluetooth receiver, which he uses with
> StreetTalk. I wanted to give it a quick try with Loadstone, I got it
> connected with out any hassle and marked a POI, I then walked about 5
> meters down the platform and marked another point. I disconnected my
> friends GPS receiver as his train arrived.
>
> I started playing with the exploration mode, and while trying to find my
> closest point and the direction I would have to travel to get to it.
> Anyway, both of the points I marked are moving around in a clockwise
> circle. I have no GPS receiver connected and would have expected that
> Loadstone would remember my last position and looking around, I would
> have been able to find the other point and that it's direction would be
> static. However, Loadstone seems to think I am somewhere in the middle
> of these two points and both are gradually moving clockwise. It takes
> about a minute and a half for one point to move from north, all the way
> around back to north.
>
> Is this suppose to happen? If so, how can you reliably determine the
> direction you should be travelling in, when the direction of the point
> keeps changing according to loadstone. If this isn't the way these
> things are suppose to work, do you have any ideas what the problem could
> be?
>
> The bluetooth receiver is a Globalsat BT338 which is a SiRF3 one, if
> that makes a difference.
>
> Hope this message makes some sense and thanks for any advice,
> Brett.
>
> Pretty cool that the world can spin with out me even having a drink,
> Smile.
>
>
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> Loadstone at loadstone-gps.com
> http://www.loadstone-gps.com/mailman/listinfo/loadstone
>


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