[postgis-devel] LRS Functions

[Christoph Spoerri]

I'm working on a set of LRS function, but my time is limited so it takes a bit 
longer then I would like.

So far I have the following functions:

createlrs: create a LRS system. The system be create with the lenght of the 
line feature or precentage as measure unit 

getmeasure: returns the position of a point along the line (in measure units)

getpoint: returns a point along the line given a measure

getline: partially done, but is very similar to the above function it returns 
a line given two points


Other functions I would like to implement:

offset: same as getline, but the returning line will be offset from the 
original line

customlrs: create a LRS with measure units given my the user (start and end 
measure would be provided by the user)

any others???


let me know if you would like to see and test what I have so far,
Christoph

On Wednesday 20 April 2005 13:11, Paul Ramsey wrote:
> Thus far, we have very few LRS functions (well, one).
>
> line_interpolate_point(geometry, proportion)
>
>      Interpolates a point along a line. First argument must be a
>      LINESTRING. Second argument is a float between 0 and 1.
>      Returns a point.
>
> This is OK, but we need two more:
>
> line_calculate_proportion(line, point)
>
>      Returns a float, representing the proportional distance the
>      point is located along the line.
>
> line_interpolate_line(geometry, proportion, direction)
>
>      Returns a line, representing the subset of the input line
>      that is the proportional distance along the line. Direction
>      determines what end to measure from. (??)
>
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