RE: longitude / latitude distance calculations

["Walden H. Leverich" <WaldenL@xxxxxxxxxxxxxxx>]

Karen,

Where are you getting your Long and Lat numbers? From zip code? For a
zip code Long and Lat are typically defined as the "center" of that zip
code, so this isn't an exact science to begin with. 

We've done a number of "locations w/in ? Miles of me" type applications
and the following formula has always worked fine:

SQRT(Power(69.1*(Lat2 - Lat1), 2) + Power(53*(Long2-Long1), 2))

That is

X = (Lat2-Lat1)*69.1 

Y = (Long2-Long1)*53

Distance = SquareRoot( X*X + Y*Y )

See
http://www.meridianworlddata.com/HTML10/distance-latitude-longitude-2.as
p for more information. 

Now, is this formula as accurate as the longer one? NO! But given that
we're dealing w/inaccurate information to begin with it's "good enough"
for most uses. If you actually have lat/long values for your customers
(from GPS in the truck?) then you may need the more accurate formula. 

-Walden

------------
Walden H Leverich III
President & CEO
Tech Software
(516) 627-3800 x11
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)