that crazy v.in.arc

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that crazy v.in.arc

Jim G-3
That crazy ARC thang,

I realize the usefulness of the v.in.arc command, but sometimes a simple
matter can be as complex as one wants it to be. Why doesn't anyone think
of converting the ARC file to a DLG file and then using v.import? I've
always had some problems with v.in.arc ( back when it was sort of GRASS3 ),
so I've often used the DLG as the standard for transfering thangs between
machines. If a GIS out there can't handle DLG format, methinks you're paying
a little too much and missing a whole heck of a lot (ERDAS comes to mind,
no offense, of course).

The real strong point of using the DLG over the v.in.arc is the fact that
you can get attributes over as well. Who wants complex soil polygons from
an ARC coverage, and then have to go back and relabel everythang? Maybe
some people like to label things, but I always prefer drinking coffee and
munching on doughnuts (personal bias, of course).

How to do? The command in ARC is ARCDLG:

Usage: ARCDLG <in_cover> <out_dlg> {point_cover} {node_cover} {node_match_tol}
              {projection_file} {x_shift} {y_shift} {header_information_file}
              {TRANS | NOTRANS}

Not as easy as just typing in the command. For all you ARC heads, look under
Appendix D in the ARC/INFO Users Guide: Volume 2 Command References, entitled
CONVERTING DLG DATA. Like most manuals, it doesn't do a very thorough job
of explaining thangs, but its probably much better than me. The critical
part here is to ADDITEMs to the .PAT and/or the .AAT, called major1 and minor1.
These two items are critical for getting the attributes over. You will
want to CALC an integer value into major1 and minor1, equal to whatever
attribute you want to bring on over. Then, the next critical part is
to specify NOTRANS in the ARCDLG command, so as to keep map coordinates as is.
Once converted, transfer the file into the dlg directory in the
appropriate location and mapset, and then run v.import. This works
successfully using SUN workstations, ARC 5.0.1, and GRASS4.0.

Confused? Better ideas? Suggestions? Love to hear them.
Write back to see which way works better. There are also numerous tricks
to get character data attributes into GRASS raster files.
I dare the GRASS community to give this a go. Double-dog-dare.
The one who does the least amount of work wins.

Jim Gasprich ([hidden email])