'=================================================================================
' Distance Calculator
'=================================================================================
' This function calculates the distance between two latitude/logitude
' coordinates. Disance can be returned as Kilometers or Miles.
'
' This function was designed for Microsoft SQL Server 2000
'
' Accepts:
'	Lat1 = Latitude of point one (decimal, required)
'	Lon1 = Longitude of point one (decimal, required)
'	Lat2 = Latitude of point two (decimal, required)
'	Lon2 = Longitude of point two (decimal, required)

'
' Provided by: http://www.zip-codes.com
'
' © 2005 Zip-Codes.com, All Rights Reserved
'=================================================================================


CREATE function dbo.DistanceCalc (@lat1 float, @lon1 float, @lat2 float, @lon2 float)
returns float

as

begin

declare @DegToRad as float
declare @Ans as float
declare @Miles as float

set @DegToRad = 57.29577951
set @Ans = 0
set @Miles = 0

if @lat1 is null or @lat1 = 0 or @lon1 is null or @lon1 = 0 or @lat2 is
null or @lat2 = 0 or @lon2 is null or @lon2 = 0

begin

return (@Miles)

end

set @Ans = SIN(@lat1 / @DegToRad) * SIN(@lat2 / @DegToRad) + COS(@lat1 / @DegToRad ) * COS( @lat2 / @DegToRad ) * COS(ABS(@lon2 - @lon1 )/@DegToRad)

set @Miles = 3959 * ATAN(SQRT(1 - SQUARE(@Ans)) / @Ans)

return (@Miles)

end