[Loadstone] Loadstone and GPS query

Shawn Kirkpatrick shawn at odyssey.cm.nu
Wed Aug 16 07:35:15 BST 2006


trying to find things within 15 to 20 feet apart would be kind of hit and 
miss. The gps accuracy is normally around 3 to 15 meters, about 15 to 45 
feet. This will depend on your receiver, the environment you're in and the 
number of satellites your receiver can pick up. The accuracy will improve if 
you can receive the waas or egnos gps correction signal. Not all receivers 
can receive this thoe. A gps can get you close to where you want to go but 
you still need basic orientation skills to find an exact spot.

On Tue, 15 Aug 2006, David Tanner wrote:

> Based on what you are saying here, if you were trying to identify and find several stores in a strip mall would a person be able to identify each store if they were within 15FT to 20FT of each other?
>
>
> ----- Original Message -----
> From: "Monty Lilburn" <monty at loadstone-gps.com>
> To: "General discussion pertaining to the Loadstone GPS program" <loadstone at loadstone-gps.com>
> Sent: Tuesday, August 15, 2006 9:51 AM
> Subject: Re: [Loadstone] Loadstone and GPS query
>
>
> : Hello Brett,
> :
> : OK, you have a few things going on here that probably aren't helping much.
> :
> : First off, are you running the latest version of Loadstone (V0.62).  It's
> : best to always be running the latest version as that is normally what any
> : support will be for.
> :
> : The first problem it would seam you are running into is your value in the
> : Max Search Radius setting.  I suspect you have it set to the old default
> : of 20000 KM which effectively is the entire world.
> :
> : From the documentation:
> :
> : 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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> : > http://www.loadstone-gps.com/mailman/listinfo/loadstone
> : >
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