ARC to GRASS
Malcolm Williamson
malcolm at cast.uark.edu
Tue Nov 7 07:00:00 EST 1995
On Mon, 6 Nov 1995, Jocelyn Aycrigg wrote:
> Hi everybody,
>
> What is the easiest, quickest, and most accurate method for translating Arc c
overages (points, lines, and polygons) to GRASS while maintaining the integrity
of the attributes. I realize I can use DXF but what other methods work?
>
> Thanks,
>
> Jocelyn Aycrigg
> USACERL at Univ. of IL
> Champaign, IL
> email: aycrigg at gis.uiuc.edu
>
Hi, Jocelyn
The following document, originally written by Craig Miller and posted by
Juan Ruiz, shows how to use the A/I ungenerate format and the GRASS command
v.in.arc. Hope you find it useful!
--
Malcolm D. Williamson - GIS Specialist E-mail: malcolm at cast.uark.edu
Center for Advanced Spatial Technologies Telephone: (501) 575-6159
Ozark Rm. 12 Fax: (501) 575-5218
University of Arkansas
Fayetteville, AR 72701
---------------------------------8<----------------cut here-----------------
IMPORTING DATA: ARC/INFO to GRASS 4.0
AUTHOR: Craig A. Miller
DATE: July 19, 1993
Importing Data from Arc/Info GIS into GRASS GIS is a two phase procedure.
PHASE 1 - Exporting from Arc/Info
1. Identify the Arc coverage that you wish to export.
o Before doing anything, copy the coverage to your Arc Info
workspace, and do your work on the duplicated coverage.
You can do this by using the Arc command "copy <incovername>
<outcovername>. Be sure to use complete paths for both
the incover and the outcover parameters.
For Example:
w /usr/rivers
copy /usr/rivers/wenatchee /usr/craig/water/wenatchee
w /usr/craig/water
Use the Arc command "DESCRIBE <CoverageName>" to answer the following:
a. Has it been projected to the coordinate system you are using
(ie. Clarke66 and UTM's - At least in our case.)
YES - Then move on to question b.
NO - Then use the Arc command project to project the coverage
correctly.
o To do this you may need to know both the current projection
information as well as what you want to project it too.
For Example:
w /usr/craig/water
project cover <wenatchee> <wenatchee.out>
input
projection utm
units meters
zone 9
parameters
output
projection utm
units meters
zone 10
parameters
end
b. Is it a polygon coverage
NO - Move on to step c.
YES - Then use the Arc command "ungenerate" once with the
lines
option, and once with the point option.
USAGE: From the ARC prompt.
ungenerate <line | point> <incover> <outcover>
ie. ungenerate line wenatchee.out wenatchee.lin
ungenerate point wenatchee.out wenatchee.lab
NOTE: It is common to use .lin to signify a line coverage, and
.lab to
signify the point coverage. This is because they will be used as
the input into grass as the line file and label file.
c. Is it a line coverage?
No - I am sorry, if it is neither a line file or a polygon file
then you will not be able to export it. I have yet to
figure out how to export a point file (Although I do have
an idea, I just haven't tried it yet. :)
YES - Then use the Arc command ungenerate line.
ie. ungenerate line wenatchee.out wenatchee.lin
3. From the arc prompt type - info
4. Turn your 'caps lock' ON.
5. enter ARC as your user name.
6. type - "select <covername.pat> if it is a polygon coverage.
or
"select <covername.aat> if it is a line coverage.
7. type items
8. Choose the columns of data that will reflect each of the
following and write down the name of the item:
ITEM1 a. point or line id's - usually covername-id
ITEM2 b. Grass category values. Must be an integer
value. Cannot contain commas. You may have
to edit this file with a text editor before
it will import correctly into GRASS (Don't
worry about this now though).
ITEM3 c. Grass attribute text. This cannot contain
any spaces, so you may have to edit this
column of data before bringing it into GRASS
too (Don't worry about this now though).
9. type - "OUTPUT <COVENAME.TXT> INIT "
10. type - "DISPLAY 5T,ITEM1,15T,ITEM2,25T,ITEM3"
11. type - "Q STOP"
12. take your caps lock off
13. type - "&sys"
14. type - "cd info"
15. type - "ls | more"
16. You should see a file called <covername.txt>.
17. Move this file to where the "Ungenerate" files from the
previous steps are being stored for export by using the UNIX
command "mv fromfile tofile"
If you followed the instructions in this document, they should be
in your arc workspace which is one directory up from where you
are now. Therefore, if you type
mv <covername.txt> ../<covername.txt> you should
be ok.
18. You should now edit out any commas in the 2nd column of
covername.txt and any spaces in the third column of covername.txt.
I have noticed that many times the first row of data is missing
values in the covername.txt file because it represents the
Arc universe polygon. You will need to fill in those columns
with data such as 0 0 NODATA.
19. You can now export your datafiles to tape, disk, or
if GRASS is running on the same machine as Arc/Info you
can copy the files (covername.lin, covername.lab, covername.txt)
to $mapset/arc
PHASE 2. THE GRASS SIDE OF THINGS.........
Use v.import as describe in the grass users manual to bring the data
across. If you are having difficulty, check to see that you have
cleaned the data up as described in step 18 of exporting from Arc.
------------------------------------8<---------------Cut-Here-----------------
Craig A. Miller
Pacific Northwest Geographics
Voice: (509) 662 4479
E-mail: cmiller at pnwg.wa.com
................................................................
Maybe you did not create previously file COVERNAME.TXT.
Good luck!
-------------------------------------------------
Juan M. Ruiz
Centro de Estudios Hidrograficos (CEDEX)
Paseo Bajo de la Virgen del Puerto 3, planta 3
28005 Madrid, SPAIN
Telephone: 335.79.51
Fax: 335.79.22
e-mail: jruiz at gea.cedex.es
-------------------------------------------------
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