[GRASS-user] overlapping areas seem valid to v.build: why?

Maris Nartiss maris.gis at gmail.com
Fri Dec 2 07:15:26 EST 2011

that makes sense.

Might I suggest to take a look at JTS Topology Suite Technical
Specifications fig. 6 that seems to display most common issues that
could be eliminated with GRASS cleaning tools too.


2011/12/2 Markus Metz <markus.metz.giswork at googlemail.com>:
> On Fri, Dec 2, 2011 at 12:43 PM, Maris Nartiss <maris.gis at gmail.com> wrote:
>> Pardon my ignorance,
>> how is possible to distinguish areas without centroids from holes?
>> And why it doesn't make sense?
> A hole is a nothing in a something. If there is no something all
> around the hole there is no hole. IOW, an area without a centroid is a
> hole if it is completely surrounded by other areas with centroids,
> otherwise that area is not a hole because it shares one or more
> boundaries with the outer void. This does not make sense logically
> because then there are two indistinguishable voids bordering each
> other. These two voids can just as well be combined into one, lest
> there is something special about one of the two voids, but that you
> could only tell if there is a centroid in one void, rendering it
> non-void.
> Markus M
>> Maris,
>> just finished converting and cleaning CAD (spaghetti) lines + points
>> to valid areas.
>> 2011/12/2 Markus Metz <markus.metz.giswork at googlemail.com>:
>>>  * for areas without centroids that are not holes. Areas without
>>> centroids that are not holes are topologically correct but do not make
>>> sense logically.

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