ARC to GRASS

[dww]

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This may be of interest to the entire list, as it seems to come up
fairly often. It may well be in the FAQ ...

On Mon, 6 Nov 1995, Jocelyn Aycrigg wrote:

> What is the easiest, quickest, and most accurate method for 
> translating Arc coverages (points, lines, and polygons) to GRASS while
> maintaining the integrity of the attributes.  I realize I can use DXF
> but what other methods work?

The only way I have found to work (for polygon coverages) is as follows:

a) In Arc:

   i)   'ungenerate' the lines to an ascii file (called eg 'cover.lines')
   ii)  'ungenerate' the label points to an ascii file (eg 'cover.points')
   iii) use INFO to export the corresponding '.pat' file to an ascii
        format. (eg 'cover.text'). LOOK AT THIS FILE to find out which
        columns then contain the identifier for the areas, and the
        category and attribute that you want in GRASS.

b) This gives you the three files to use with v.in.arc; put these in 
   a directory called 'arc' in one of your mapsets (for example you
   could create a directory Mydata/PERMANENT/arc/). Then use v.in.arc
   as follows, using the column names you noted down:

v.in.arc type=poly  lines_in=cover.lines points_in=cover.points 
         text_in=cover.text attvector_out=whatever_you_want
         idcol=? catcol=? [attcol=?]

c) Run v.support, and see how many point-to-area operations don't work,
   then use v.digit or v.digit2 to fix these. 


For lines, simply ungenerate the lines and .pat bit. Then give type=line
to v.in.arc.

David Wheatley 
Department of Archaeology,
University of Southampton,
Highfield, Southampton, S017 1BJ