Ok I ,m not 100% here but I feel I'm getting closer to solving my problem.
Got this handy little document online that helps with these sort of
equations,
I will post the full url's for anyone interested.
Distance between points
The great circle distance d between two points with coordinates {lat1,lon1}
and {lat2,lon2} is given by:
d=acos(sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(lon1-lon2))
A mathematically equivalent formula, which is less subject to rounding error
for short distances is:
d=2*asin(sqrt((sin((lat1-lat2)/2))^2 +
cos(lat1)*cos(lat2)*(sin((lon1-lon2)/2))^2))
So this is what I have done..
<!--- I need to get thefurthest west --->
<cfquery name="qry_westLon" datasource="#application.dsn#"
username="#application.gateway#" password="#application.key#">
SELECT MAX(Lon) as maxlon
FROM dbo.vehicles
WHERE vowner = 888
</cfquery>
<cfset paramWestLon = qry_westLon.maxlon>
<cfquery name="qry_westLonNowLat" datasource="#application.dsn#"
username="#application.gateway#" password="#application.key#">
SELECT lon, lat
FROM dbo.vehicles
WHERE lon = #paramWestLon# and vowner = 888
</cfquery>
<cfset paramWestLat = qry_westLonNowLat.lat>
<!--- * now I need to get the furthest east --->
<cfquery name="qry_eastLon" datasource="#application.dsn#"
username="#application.gateway#" password="#application.key#">
SELECT Min(Lon) as minlon
FROM dbo.vehicles
WHERE vowner = 888
</cfquery>
<cfset paramEastLon = qry_eastLon.minlon>
<cfquery name="qry_eastLonNowLat" datasource="#application.dsn#"
username="#application.gateway#" password="#application.key#">
SELECT lon, lat
FROM dbo.vehicles
WHERE lon = #paramEastLon# and vowner = 888
</cfquery>
<cfset paramEastLat = qry_westLonNowLat.lat>
<!--- * ok gat my variable for west longtitude(paramWestLon)
latitude(paramWestLat)
and east longtitude(paramEastLon)
latitude(paramEastLat)
* so now do my equation to get distance between
point --->
<cfset d =
acos(Sin(paramWestLat)*sin(paramEastLat)+cos(paramWestLat)*cos(paramEastLat)
*cos(paramWestLon-paramEastLon))>
<cfoutput>#d#</cfoutput>
I'm not sure if this will work but when I run this I get this error
An error occurred while evaluating the expression:
d =
acos(Sin(paramWestLat)*sin(paramEastLat)+cos(paramWestLat)*cos(paramEastLat)
*cos(paramWestLon-paramEastLon))
Error near line 30, column 8.
----------------------------------------------------------------------------
----
Parameter 1 of function Sin which is now "" must be a stk_real number
does it think my variable is a string, I'm not ashamed to say that I,m not
sure what 'must be a stk_real number' is telling me.
Many thanx in advance.
JMC
-----Original Message-----
From: Philip Arnold - ASP [mailto:[EMAIL PROTECTED]]
Sent: 15 March 2001 12:25
To: CF-Community
Subject: RE: longtitude and latitude
> Maybe, or maybe not, a cf question but I feel the audience is of the right
> kaliber of intelligence to be asking anyway!!
>
> I'm working with Longtitude and latitude co-ordinates at the moment,
>
> what I would like to do is work out the differnce in Kilometers (or miles)
> between two references i.e.
>
> Lontitude 5.48084768538759 and longtitude -5.9417692388158496
>
> I am pulling both co-ordinates from a cfquery and then setting a
> zoom level with a centre point depending on the distance between the
> two points.
>
> Any help on this matter would be appreciated....
OK, since Longtitude and Latitude don't have a globally set standard
distance between them
If you have a calculation for the global positioning, then I'm sure there
must be a way to do it
Philip Arnold
Director
Certified ColdFusion Developer
ASP Multimedia Limited
T: +44 (0)20 8680 1133
"Websites for the real world"
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