Re: [Geotools-gt2-users] position on LineString that is closest to Point

[Schuster S. <ste...@ge...>]

Hi again,

 

while trying to implement my suggested solution, I realised that it is not
only ugly, but it also doesn’t work, as there is no “CIRCLE” Geometry I
could use.

Therefore, I really need help, thanks in advance!

 

Stefan

 

 

  _____  

Von: Schuster Stefan [mailto:ste...@ge...] 
Gesendet: Donnerstag, 4. März 2010 12:42
An: geo...@li...
Betreff: [Geotools-gt2-users] position on LineString that is closest to
Point

 

Hi,

 

Assume I have a Point p and a  LineString ls. 

 

By the statement

double dist = ls.distance(p) 

I easily can figure out the distance between them. 

 

But now I want to now the Point p_cut on the LineString that was used to
calculate the distance, more accurate I want to know the length of the
LineString from the beginning to the Point p_cut.

 

Any suggestions?

 

My first idea was to create a circle around Point p with a radius of
distance, and the intersection between this circle and the LineString is
point p_cut. 

To get the length of LineString from the beginning to this point the
following algorithm could do it:

 

Create new empty line String lsCopy

Add first coordinate of the original LineString to lsCopy

DO

            Add next coordinate of the original LineString to lsCopy

            IF NOT lsCopy intersects p_cut THEN

                        Continue;

            ELSE

                        Remove last coordinate from ls_copy

                        Add coordinates of p_cut to ls_copy

WHILE original LineString has next coordinate                        

 

 

I have not yet tried it, I guess it would work but this looks very ugly and
I wonder if there is a more beautiful solution?

 

Thanks for help

 

Stefan