Found a better solution here: http://www.movable-type.co.uk/scripts/latlong.html

It's javascript code to calculate the distance between two lat-long
coordinates!



On Feb 2, 1:17 pm, James <[email protected]> wrote:
> Thank you very much, Larry! Looks like a winner! :)
>
> On Feb 2, 12:46 pm, "[email protected]" <[email protected]>
> wrote:
>
>
>
>
>
>
>
> > On Feb 2, 7:05 am, James <[email protected]> wrote:
>
> > > Thank you for your response, Rossko!
>
> > > As you stated, GPS accuracy is something important to take into
> > > account. For the purpose that I intend, accuracy within the 20-100m
> > > range would be acceptable. My confusion is what the best approach is
> > > for determining when a user has gotten within this 20-100m range of
> > > the destination? I will have their geolocation and the destination
> > > location, but what values should I compare to determine if they are
> > > within this 20-100m area?
>
> > calculate the distance between them and compare it to a threshold.
> > See the geometry 
> > library:http://code.google.com/apis/maps/documentation/javascript/geometry.html
>
> >   -- Larry
>
> > > On Feb 1, 8:07 pm, Rossko <[email protected]> wrote:
>
> > > > That's entirely up to you.
> > > > Factors to take into account:
> > > > GPS are not accurate to nanometres.
> > > > Roads, etc, are physical objects with dimensions.  If your user is 20m
> > > > away he may be on the other side of the road to your target - is that
> > > > good enough for you? We can't decide for you.
> > > > Buildings, plots, are physical objects etc.   If a building has a 100m
> > > > frontage when does your user arrive at it?  If they are walking (you
> > > > didn't say) that might be more important.
> > > > Directions results take you to nearest point that they know of, to the
> > > > point they think you are trying to get to.  You might specify an
> > > > address (you didn't say) which geocodes e.g. to a rooftop.  Directions
> > > > can never quite get to that from the public street.
> > > > Or, if geocoding is poor in the area or country you are operating in
> > > > (you didn't say), Directiions may only take you to the end of the
> > > > street and not a specific address.
>
> > > > I'd think I'd start experimenting with proximity in the 20 to 100m
> > > > range and see how it goes.- Hide quoted text -
>
> > > - Show quoted text -

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