[GRASS-dev] v.clean meters against feets

[Markus Metz]

On Wed, Aug 27, 2014 at 10:01 AM, Luca Delucchi <lucadeluge at gmail.com> wrote:
> Hi everybody,
>
> I'm testing v.clean with meters and feet projection system.
> I'm trying to run v.clean in the same map and with the same
> parameters, but I obtain a different result. For the testing I'm using
> zipcodes_wake map of nc_spm_08
>
> Here my procedure:
>
> - download nc_spf location from here [0]
> - reproject zipcodes_wake from nc_spm_08 to nc_spf
>
> - run v.clean on meters location with "v.clean in=zipcodes_wake
> out=zipcodes_wake_clean tool=rmarea thre=10000000" the result is
>
> Number of nodes: 106
> Number of primitives: 166
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 135
> Number of centroids: 31
> Number of areas: 31
> Number of isles: 2
>
>
> -  run v.clean on feet location with "v.clean in=zipcodes_wake
> out=zipcodes_wake_clean tool=rmarea thre=107638674"
>
> Number of nodes: 84
> Number of primitives: 103
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 93
> Number of centroids: 10
> Number of areas: 10
> Number of isles: 1
>
> The threshold in feet should be the same of the meters one because:

The threshold must always be in meters, also if the location's units
are not meters, because G_area_of_polygon() is used to calculate area
sizes which always returns square meters. This was wrong in the manual
of v.clean, fixed in r62047,8 (trunk, relbr70).

Markus M

>
> 1 meters is 0.3048006096012192 feet (according with g.proj output)
>
> and
>
> 10000000 squared meters is 107638674 squared feet ( 10000000 / 0.3048^2 )
>
> I expected the same output map, but this not happen; I'm wrong or
> there is something wrong in the v.clean code?
>
>
> [0] http://grass.osgeo.org/sampledata/north_carolina/nc_spf.tar.gz
>
> --
> ciao
> Luca
>
> http://gis.cri.fmach.it/delucchi/
> www.lucadelu.org
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