Re: [udig-devel] How to create a grid of features in a polygone

[Ingmar Eveslage <eveslage@xxxxxxxxx>]

Just for an update: i (to be honest: a colleague) found this class:

http://udig.refractions.net/files/docs/api-geotools/org/geotools/referencing/GeodeticCalculator.html

i think this could help to do the job in a plugin source code.

greats ingmar

Am 30.03.2008 um 19:20 schrieb andrea antonello:
> Hi Ingmar,
>
> > > > Good idea with to intersection of the horizontal and vertical  
> > > > lines.
> > > > But how do i create the lines with the constant spacing?
> > > >
> > > > i manged to get the envelope from a polygone with 5 coordinates  
> > > > likes
> > > > this:
> > > >
> > > > (13.68264407681451, 53.818121066825206, NaN)
> > > > (14.101893321395334, 53.818121066825206, NaN)
> > > > (14.101893321395334, 54.112935604110326, NaN)
> > > > (13.68264407681451, 54.112935604110326, NaN)
> > > > (13.68264407681451, 53.818121066825206, NaN)
> > > >
> > > > a nice bounding box. and now?
> > > >
> > > > the first horizontal line is
> > > >
> > > > (13.68264407681451, 54.112935604110326, NaN) (14.101893321395334,
> > > > 54.112935604110326, NaN)
> > > >
> > > > the upper left corner to the upper right corner. how do i get the
> > > > next
> > > > point for the Y coordinate with a distance of, lets say, 200m?
> > > >
> > > > (13.68264407681451, ??, NaN) (14.101893321395334, ??, NaN)
> > >
> > > You are dealing with lat-long coordinates, so it doesn't make  
> > > sense to
> > > talk metric.
> > > You could say: "...point for the Y coordinate with a distance of,  
> > > lets
> > > say, 60'?"
> > > If you need metric, you should first reproject the layer into your
> > > local metric system and then do maths with your metric coordinates.
> > >
> > > Is that the problem you have?
> >
> > Yes, i think this is my problem. I can not deal with a distance of
> > 60'. How can i do this projection? I am not realy good in this geo-
> > stuff. sorry.
> >
> > lets resume what i should do:
> >
> > i have lat/lon -> project in metric coodinates (km, meter) -> take  
> > the
> > line and calculate a parallel line with distance of 200m -> reproject
> > to lat/lon to get the depending coordinates.
> >
> > is this possible? how?
>
> It is possible.
> Load your shapefile or whatever. Export it. When you export it, you
> can choose the CRS for the exported map. Choose the epsg for your
> projection. That one you have to be aware of, because if you do not
> have exactly the info required, you could have shifts and distortions.
>
> Once exported it is also reprojected. Load the new shapefile and you  
> are there.
> Now the part with the lines and 200m comes.
>
> Onces you have the final points, you can reproject them nack, even if
> they are reprojected *for visualization only* on the fly.
>
> Andrea
>
>
> > Thanks forward.
> >
> >
> >
> > > Ciao
> > > Andrea
> > >
> > >
> > >
> > > > Thanks again. Ingmar
> > > >
> > > > Am 30.03.2008 um 15:21 schrieb andrea antonello:
> > > >
> > > >
> > > > > > i have a little "geospatial" question. I want to draw polygones
> > > > > > on a
> > > > > > polygone layer and then start a wizard which fills the polygone
> > > > > > with
> > > > > > features (with a point geometry). All features have the same
> > > > > > distance
> > > > > > (lets say 100m to each other) and all are in the area of the
> > > > > > polygone.
> > > > > >
> > > > > > Sounds like a not so difficult problem, but i hope that there  
> > > > > > is a
> > > > > > nice way to program this. perhaps i should use the gridcoverage
> > > > > > class?
> > > > > > i realy dont know where to start.
> > > > >
> > > > > Hi Ingmar,
> > > > > I think it is more a JTS related question.
> > > > > What I would probably do (I'm writing as I'm thinking) is to  
> > > > > create
> > > > > the grid of lines at the wanted distances one from the other.
> > > > > The horizontal lines and vertical lines should stay in two  
> > > > > different
> > > > > multilinestring geometries. Then through
> > > > >
> > > > > resultPointGeom = horizontalLines.intersection(verticalLines)
> > > > >
> > > > > you gain all the points you wanted to have into the resulting
> > > > > geometry.
> > > > > After that you will have to get from those only the ones inside  
> > > > > the
> > > > > polygon, which I assume can be done through another intersection
> > > > > between polygon and resultPointGeom.
> > > > >
> > > > > Ciao
> > > > > Andrea
> > > > >
> > > > >
> > > > >
> > > > > > Thanks for any advice.
> > > > > >
> > > > > > Greats Ingmar
> > > > > > _______________________________________________
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