[GRASS-user] using v.line.center
tutey at o2.pl
Fri Jun 6 04:32:09 EDT 2008
Markus Neteler pisze:
> On Thu, Jun 5, 2008 at 7:38 PM, Maciej Sieczka <tutey at o2.pl> wrote:
>> Manuel Sangiao pisze:
>>> WARNING: Cannot get point on line: cat=927 offset=89379.795093 (line
>>> lenght=2.219076) P 927 927 89379.795093
>>> I guess the reason for this error is the projection (mapset?) unit.
>>> The projection unit(s) in my mapset is degree(s). And the length
>>> units are meters.
>> v.line.center as it is can't work in latlon Location. It uses v.to.db
>> for length calculation, which cannot measure in degrees,
> I think it can... from the man page:
> "When calculating perimeters in Latitude-Longitude locations, the geodesic
> distance between the vertices is used.
v.line.center uses v.to.db to calculate lengths of input vector lines,
which then are fed into v.segment as offsets to create lines' center points.
v.segment expects offsets in units of the Location. If these are degrees
we have a problem because v.to.db can't calculate length in degrees. It
supports the following units:
Therefore, v.line center can't work in latlon locations.
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