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

[Ingmar Eveslage]

Hi Andrea,

Am 30.03.2008 um 17:32 schrieb andrea antonello:
> Hi Ingmar,
> now I see your problem...
>
>> 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?

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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>>>> http://udig.refractions.net
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>>
>> _______________________________________________
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>> http://udig.refractions.net
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>>
> _______________________________________________
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> http://udig.refractions.net
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