Moving a Point along a Path in SQL Server 2008

Question

I have a geography field stored in my database, holding a linestring path.

I want to move a point n meters along this linestring, and return the destin

Answer 1

I used Daniel's answer from above, but I had to fix the "func_MoveAlongPath" signature to

CREATE FUNCTION [dbo].[func_MoveAlongPath](@path geography, 
                                       @distance **float**, 
                                       @index int = 1)

The int would returned wrong results, because it would round the values in the recursive calls. I then converted it into an iterative version, since the recursive one couldn't handle larger distances in the sample data I had:

CREATE FUNCTION [dbo].[func_MoveAlongPathIter](@path geography, 
                                               @distance float)   
RETURNS geography
AS
BEGIN
    DECLARE @index          int = 1;
    DECLARE @result         geography = null;
    DECLARE @num_points     int = @path.STNumPoints();
    DECLARE @dist_to_next   float;
    DECLARE @comul_distance float = 0;

    WHILE (@index < @num_points - 1) AND (@comul_distance < @distance)
    BEGIN
        SET @dist_to_next = @path.STPointN(@index).STDistance(@path.STPointN(@index + 1));
        SET @comul_distance += @dist_to_next;
        SET @index += 1;
    END

    SET @result = [dbo].[func_MoveTowardsPoint](@path.STPointN(@index - 1),
                                                        @path.STPointN(@index),
                                                        @distance - (@comul_distance - @dist_to_next));
    RETURN @result;
END