[postgis-devel] LRS Functions
Christoph Spoerri
cspoerri at cavtel.net
Wed Apr 20 18:51:37 PDT 2005
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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