Is there something like "v.report"? Can I mask vectors?

[Michael Shapiro]

There is a "v.report" under src.contrib/SCS/vector/v.report and a
manual  page as well in the 4.0 release. You will have to compile
it since it isn't automatically compiled when you compile  GRASS.
The  manual  entry  specifically says that the current region and
mask are ignored.

GRASS raster library functions clip raster data  to  the  current
region  and mask them as well. However, GRASS vector libraries do
not do "clipping" to  the  current  region.   Also  they  do  not
attempt to "mask" vector data. Hence the behavior of v.report.

It would  be  reasonable  (and  not  too  difficult)  to  enhance
v.report to work in the current region. Perhaps this tool will be
enhanced to do this in the near  future  (but  probably  not  for
4.1).   I would not expect v.report (or other vector tools) to be
enhanced to do "masking" of vector data.

|
|Folks,
|  I'm looking for the simplest way (in GRASS) to solve a problem of
|the following sort:
|
|Given a layer of townships (polygons), and a layer of roads (vectors),
|compute the length of road in a given township.
|
|I started out converting the polygons to raster regions and producing
|a mask, and then converting the roads to raster and running r.report.
|
|But this generates areas or cell counts, which are at best a crude way
|to measure lengths.
|
|It seems that vector displays are unaffected by masks, and I also cannot
|find any tool to compute the length of vectors in a vector file.  If I
|could mask the vector file and then run something like a "v.report" I
|think I'd have it.  SO:
|
|a) Is there a way to mask vector files?
|b) Does someone have something like a "v.report"?
|	(I found v.area, which must do the same calculation to get
|	the perimeter values it reports).
|
|Thanks!  Steve Frysinger
|
|



Michael