[GRASS-dev] integrate v.concave.hull into v.hull [was point cloud analysis: new features]]

[Markus Neteler]

On Sun, Jan 11, 2015 at 9:03 PM, Markus Metz
<markus.metz.giswork at gmail.com> wrote:
> On Fri, Jan 9, 2015 at 9:35 AM, Moritz Lennert wrote:
>> On 08/01/15 23:46, Markus Metz wrote:
>>>
>>> On Mon, Jan 5, 2015 at 12:17 PM, Benjamin Ducke  wrote:
>>>> Thanks Markus, this is excellent progress.
>>>> It seems to me that the approximation of cluster shapes from grouped
>>>> points is a generic problem that would best be solved with a separate
>>>> module. As long as the shapes are roughly convex, the existing v.hull
>>>> should work fine. For concave shapes, AFAIK things become messy because
>>>> common methods such as alpha shapes require the user to provide
>>>> threshold values.
>>>
>>> This is true, but v.concave.hull [0] could help ;-)
>>
>> All these great addons !
>>
>> For this particular one: would it be interesting / possible to integrate it
>> directly into v.hull ?
>
> No, because v.hull is a C module and v.concave.hull a script which
> does not use v.hull at all. Instead, v.concave.hull cleans the output
> of v.delaunay to create concave hulls.

I have a similar problem: imagine a set of contour lines which
describe the bathymetry of a lake, so essentially contour lines which
are closing a polygon but consist of different lines.

I would like to get the respective polygon representation, i.e. the
outer lines only and those turned into a polygon.

I just tried v.concave.hull on it, however, it expects points and not lines.
Does anyone have an idea how to achieve that?

thanks
markusN