[GRASS-user] Re: Extracting the external boundary of a vector file

[Edward Tomlinson]

Hi list,


My apologies. The island is actually and obstacle so I still need to include
it.

However, is there a better way of achieving the external boundary using the
centroids or points??

Thanks,

Ed

2008/5/29 Edward Tomlinson <e.j.tommo at gmail.com>:

> Hi list,
>
> I have a whole bunch of data from an RTK GPS. File exists as a MapInfo
> file. Imports into grass fine with area and centroids.
>
> My problem is however, i want to create another vector file that contains
> the mask or the external (an internal island) boundary.
>
> I have been able to create the external boundary fine through the
> following.
> v.category (delete categories)
> v.category (add category as 1 for all)
> v.dissolve (combine all boundaries with common category)
>
> This is great and works fine for the external boundary. However there is
> meant to be an island in there. Somewhere along the way (i think after the
> second call to v.category) it fills that island in.
>
> Has anyone got any hints or ideas?
>
> Essentially i am trying to create this vector to generate a mask for
> further interpolation of the point heights. I am assuming that i need this
> island removed (as there is no point data for it) otherwise it is going to
> effect the interpolation.
>
> Thanks for your time.
> Ed
>
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