I have just got this to work exactly the way I want it,
I have wrote a UDF with the correct formula in it now
and it seems to be 100% accurate,
the UDF takes into account that your LAT and LON values
are in Degree decimal format,
<!---UDF distance Formula||--->
<CFSCRIPT>
//calculate the Deltas
function distance(lat1,lat2,lon1,lon2){
km=6367;
deltaLon=twoRadians(lon1)-twoRadians(lon2);
deltaLat=twoRadians(lat1)-twoRadians(lat2);
//intermediate values
intMedVal = sin2(deltaLat/2) + cos(twoRadians(lat1)) *
cos(twoRadians(lat2)) * sin2(deltaLon/2);
//the great circle distance in radians
gcd = 2 * arcSin(getMin(1,Sqr(intMedVal)));
//multiply the the radians by the radius to get the
distance in specified units
d = km * gcd;
//this only applies to us (ANDRONICS.CO.UK)
//it relevant to the vendor that is displaying the
map data
//the map is coming back in rectangular format they
use the length as the zoom distance
//we multiply it by 2 two get an equal zoom distance
from top to bottom
d = round(d * 2);
}
//Convert to Radians
function twoRadians(currDegree){
(currDegree * (Pi()/180));
}
function sin2(currVal){
(1 - cos(2*currVal))/2;
}
function arcSin(x){
atn(x/Sqr(-x * x + 1));
}
function getMin(y,z){
if(y lte z){
getMin=y;
}else{
getMin=z;
}
}
</CFSCRIPT>
<CFSET
ATTRIBUTES.D=distance(maxLatitude,minLatitude,maxLongitude,minLongitude)>
Respectfully,
J
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