[GRASS-user] Query: number of 'areas' reported in v.build output does not necessarily represent different geographical areas

[Markus Metz]

On Wed, May 8, 2013 at 5:17 PM, Vincent Bain <bain at toraval.fr> wrote:
> Thank you Markus,
> good news !
> how long has it been implemented ?

The option to snap boundary vertices has been there ever since. The
suggestion of a reasonable (assuming floating point rounding errors)
threshold for snapping has been added 3 weeks ago, on April 19th.

BTW, if the input polygons are supposed to not overlap each other, the
number of centroids should be identical to the number of input
polygons (needs to be added to the manual).

Markus M

>
> Vincent
>
>
> Le mercredi 08 mai 2013 à 16:27 +0200, Markus Metz a écrit :
>> On Wed, May 8, 2013 at 11:56 AM, RichardC <richtcooper at hotmail.com> wrote:
>> > Thanks for your fast replies. I'll certainly take a look at the script.
>> >
>> > Snapping with v.clean seems to work quite nicely on this occasion:
>>
>> Easier (and maybe safer) would be to snap already during import with
>> v.in.ogr snap=
>>
>> BTW, in the latest versions of GRASS, v.in.ogr suggest a snapping
>> threshold if errors are encountered.
>>
>> Markus M
>>
>> >
>> >                 snap lines/boundaries   0.000001
>> >                 break lines/boundaries  0.00
>> >                 remove duplicates       0.00
>> >                 remove small angles at nodes    0.00
>> >                 break lines/boundaries  0.00
>> >                 break polygons  0.00
>> >                 remove duplicates       0.00
>> >                 remove lines/boundaries of zero length  0.00
>> >                 remove duplicate area centroids 0.00
>> >
>> > Output:
>> > Number of nodes: 774
>> > Number of primitives: 786
>> > Number of points: 0
>> > Number of lines: 0
>> > Number of boundaries: 776
>> > Number of centroids: 10
>> > Number of areas: 14
>> > Number of isles: 2
>> > Number of areas without centroid: 4
>> >
>> >
>> >
>> >
>> >
>> > --
>> > View this message in context: http://osgeo-org.1560.x6.nabble.com/Query-number-of-areas-reported-in-v-build-output-does-not-necessarily-represent-different-geographics-tp5052007p5052033.html
>> > Sent from the Grass - Users mailing list archive at Nabble.com.
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