Hello Pete,
> I think you are referring to the "extractPoint" function. But the function
> selects the Point between in a fraction between [0,1]
No, it takes a distance in whatever units you are using for your
geometries. For example, assuming a Cartesian space (and without
checking line direction here)...
double interval = 50d;
double distance = interval;
double end = myLine.getEndPoint().x;
LengthIndexedLine lil = new LengthIndexedLine(myLine);
List<Coordinate> points = new ArrayList<Coordinate>();
while (true) {
p = lil.extractPoint(distance);
if (p.x > end) break;
points.add(p);
distance += interval;
}
> and i like to have
> something like "find the lat/lon position with the distance of 50meter from
> the beginning"
JTS doesn't know about non-Cartesian geometries like lat-long. You
can use lat-long coords and if the distances involved are very small
it will be ok, but as they get larger the calculations will become
more inaccurate.
> I belive i have to convert my wgs84-linestring to use the extractPoint
> function the way i want it... but i don't really know how...
You are probably best re-projecting your coords into a system that is
relevant to the area that you are dealing with for accuracy. Select a
projection (e.g. UTM Zone 55S for me here in Sydney) and find it's
EPSG code (http://www.epsg-registry.org/).
Then one way to reproject your geometry (someone else here will surely
point out a more elegant way !)
// not showing exception handling here...
CoordinateReferenceSystem inCRS = DefaultGeographicCRS.WGS84; // you
are using this ?
CoordinateReferenceSystem outCRS = CRS.decode( someEPSGCode );
MathTransform in2out = CRS.findMathTransform(inCRS, outCRS);
MathTransform out2in = in2out.inverse();
LineString trLine = JTS.transform( latLongLine, in2out );
Hope this helps
Michael
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