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9.0

Get Latitude/Longitude for a Known Distance From Another Latitude/Longitude

Asked by wwarby in GIS & GPS Programming, Math & Science, MS SQL Server

Tags: T-SQL

I need a pair of T-SQL functions that look something like the attached code snippet. Essentially, my aim is to create a bounding box 200m around a known lat/lng so I need to get the co-ordinates 200m due east and due north from the known point. I have a function for calculating the distance between two known Latitudes/Longitudes (that was easy to find on the web) but not being a mathematician, I don't know how to refactor the equation for this purpose.

The reason I need this is a little convoluted but I'll gladly explain if asked. Ideally, the solution would use the same mathematics as my existing distance calculator function, just re-organised to get the lat/lng values instead of the distance, but I'll take any solution that works ;) 
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CREATE FUNCTION dbo.LatOffset(@Lat FLOAT, @Lng FLOAT, @MetresOffset) 
	RETURNS FLOAT
	AS
	BEGIN
		--do some magic and return the Latitude @MetresOffset due north of the point (@Lat, @Lng)
	END
 
CREATE FUNCTION dbo.LngOffset(@Lat FLOAT, @Lng FLOAT, @MetresOffset) 
	RETURNS FLOAT
	AS
	BEGIN
		--do some magic and return the Longitude @MetresOffset due east of the point (@Lat, @Lng)
	END
 
 
 
--my existing distance calculation function
CREATE FUNCTION dbo.Distance(@Lat1 FLOAT, @Lng1 FLOAT, @Lat2 FLOAT, @Lng2 FLOAT) 
	RETURNS FLOAT
	AS
	BEGIN
		RETURN(6378.14 * ACOS((COS(RADIANS(@Lat1)) * COS(RADIANS(@Lng1))) * (COS(RADIANS(@Lat2)) * COS(RADIANS(@Lng2))) + (COS(RADIANS(@Lat1)) * SIN(RADIANS(@Lng1))) * (COS(RADIANS(@Lat2)) * SIN(RADIANS(@Lng2))) + SIN(RADIANS(@Lat1)) * SIN(RADIANS(@Lat2))))
	END
[+][-]11/25/08 08:33 AM, ID: 23035783Accepted Solution

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About this solution

Zones: GIS & GPS Programming, Math & Science, MS SQL Server
Tags: T-SQL
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Solution Provided By: deighton
Participating Experts: 3
Solution Grade: A
 
[+][-]11/25/08 03:14 PM, ID: 23038510Assisted Solution

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[+][-]11/25/08 03:21 PM, ID: 23038547Expert Comment

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[+][-]11/26/08 12:41 AM, ID: 23040409Author Comment

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[+][-]11/26/08 01:52 AM, ID: 23040698Expert Comment

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