[gps-talkusers] Re: intersections and way points

Allen,

I am not completely sure from your explanation how you were calculating a 
route.

The 30 foot inaccuracy of the GPS is in addition to any street map data 
errors. If you did an automatic pedestrian route, waypoints would be have 
set at the middle of each street intersection. Once you physically arrive 
at a corner, the mid point of that intersection could easily be 50 feet 
away plus the street at could be off by 20 or 30 feet. Add this all up and 
worse case, you could have a 100 foot offset from your actual position.

This doesn't mean there is a 100 foot inaccuracy because of course you are 
not wanting to be in the middle of the intersection.

To help deal with these factors, the BrailleNote says Near an intersection 
when you are less than 100 feet from the theoretical mid point. It doesn't 
tell you a distance.

I have a street near my house which shows up as about 75 feet North of 
where the street actually is when I am walking on it with GPS. This isn't 
always the case but it does happen. You learn soon enough how to transpose 
that information into something useful.

The route software also knows to skip ahead to subsequent waypoints even if 
you don't get close enough to trigger each point.

Another item to check. Make sure your unit is set to Auto Increment 
Waypoint on with the RA key. It defaults to Turns Only, which you can 
change with the RM command. When Turns Only is on, you won't hear Arrive 
announcements at each intersection, only bleeps.

Mike

At 12:23 PM 7/24/2004, you wrote:
>Hi, listers,
>
>I took a walk and at the one mile point I got the nearest address and
>created an automatic route back to my apartment.  But the strange thing was
>the intersections set at way points were out of sync with the multiple
>announcement of intersections.
>Also when I approached an intersection set as a way point my Voice Note
>never said, "arrived", and the way points were off by 100 feet or more.  I
>thought the range was 30 feet either way.
>
>Did I do something wrong?
>
>Thanks
>
>
>Allen
>The Maynframe, maynframe@xxxxxxxxxxxxx
>Web Page:  www.fantasystorm.net


Michael G. May

CEO Sendero Group

Developers and distributors of BrailleNote GPS
Now distributing BrailleNote, VoiceNote, Miniguide, The Tissot Silen-T 
tactile watch and the ID Mate, bar code reader

MikeMay@xxxxxxxxxxxxxxxx
http://www.SenderoGroup.com

(530) 757-6800, Fax (530) 757-6830, Mobile (530) 304-0007
Sendero Group, LLC
1118 Maple Lane, Davis, CA 95616-1723, USA

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Longitude, 121 45 40.145 West

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