[gdal-dev] Identification of neighbouring OGRGeometries

[Chaitanya kumar CH]

Alex,

There can be more than two neighbours for an isohypse (elevation contour
line). However, all the neighbours will have the same elevation or one
elevation interval up or down. So, if you created elevation contours for
every 10 meters, a contour at elevation 40 can have neighbours with
elevation 30, 40 and 50 meters. You may have to search for proximity with
all these contours.

IMO, an easier and faster way to guess this is by comparing the minimum and
maximum elevation values in the raster's area. This will also give a better
idea of the terrain's topology.

On Thu, Jul 8, 2010 at 11:54 AM, Alexander Plum <Alexander.Plum at cae.de>wrote:

> Hi,
>
> first of all I'm collecting OGRGeometries from OGRFeatures. The OGRFeatures
> exist in a OGRLayer in which the function 'GDALContourGenerate' has written.
> I put these OGRGeometries (these geometries should later be painted) into a
> std::vector. Before putting the next OGRGeometry into this vector it shall
> be checked
> which neighbouring OGRGeometries the current OGRGeometry possesses. But I
> do not know how I get these (two) neighbouring OGRGeometries.
> Later on the distance to both OGRGeometries shall be calculated with help
> of the function 'OGR_G_Distance'. If the distance is too small the current
> OGRGeometry will not be put
> into the vector collecting OGRGeometries.
>
> I hope you can get me and thanks for your support,
>
> Alex
> ________________________________________
> Von: Chaitanya kumar CH [chaitanya.ch at gmail.com]
> Gesendet: Mittwoch, 7. Juli 2010 20:05
> An: Alexander Plum
> Betreff: Re: [gdal-dev] Identification of neighbouring OGRGeometries
>
> Alex,
>
> Can you explain me what 'highline' means?
>
> On Wed, Jul 7, 2010 at 5:01 PM, Alexander Plum <Alexander.Plum at cae.de
> <mailto:Alexander.Plum at cae.de>> wrote:
> Look,
>
> I am working on a function which paints OGRGeometries representing
> highlines.
> Before painting them I want to make sure wether the new OGRGeometry should
> be painted or not. If the distance to the two neighbours is too near to its
> both neighbours, the
> new highlinie should not be painted. I am looking foward to employ the
> function OGR_G_Distance() for this case.
> But first of all I want to identify the new highline's two neighbours...
>
> Best regards,
> Alex
> ________________________________________
> Von: Chaitanya kumar CH [chaitanya.ch<http://chaitanya.ch>@gmail.com<
> http://gmail.com>]
> Gesendet: Mittwoch, 7. Juli 2010 13:19
> An: Alexander Plum
> Cc: gdal-dev at lists.osgeo.org<mailto:gdal-dev at lists.osgeo.org>
> Betreff: Re: [gdal-dev] Identification of neighbouring OGRGeometries
>
> Alex,
>
> If I understand you correctly, the method OGRGeometry::Touches() can help
> you.
> You can see it's description and similar functions at
> http://gdal.org/ogr/classOGRGeometry.html
>
>
> On Wed, Jul 7, 2010 at 2:17 PM, Alexander Plum <Alexander.Plum at cae.de
> <mailto:Alexander.Plum at cae.de><mailto:Alexander.Plum at cae.de<mailto:
> Alexander.Plum at cae.de>>> wrote:
> Hello there,
>
> is it possible to identify the two neighbouring OGRGeometries of another
> OGRGeometry??
> Therefore I miss an adequate function in the GDAL-API.
>
> Greets,
> Alex
>
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>
>
> --
> Best regards,
> Chaitanya kumar CH.
> /tʃaɪθənjə/ /kʊmɑr/
> +91-9494447584
> 17.2416N 80.1426E
>
>
>
> --
> Best regards,
> Chaitanya kumar CH.
> /tʃaɪθənjə/ /kʊmɑr/
> +91-9494447584
> 17.2416N 80.1426E
>



-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
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