A variety of GRASS programs exist to import and export data to and from GRASS. The v.in.arc program will convert vector data in ARC/INFO's "Generate" format to GRASS's vector file format, and bring it into the user's current GRASS mapset. The files to be imported to GRASS must first have been exported from ARC/INFO using the ARC/INFO Ungenerate command, and may represent either linear features ("line coverage") or areal features ("polygon coverage"). The ARC/INFO User's Guide describes how files containing linear and polygonal features can be exported from ARC/INFO, in a section detailing the use of the Ungenerate command.
Note: The ARC coverage must be set to single precision before running Ungenerate. If it is not, first copy it to another coverage that is set to single precision, then run Ungenerate.
Once converted with the ARC/INFO Ungenerate command, the files to be imported into GRASS must be placed in a directory named arc in the user's current mapset. If the arc directory does not exist, it must be created (e.g., with the command mkdir $LOCATION/arc) before copying the ARC-INFO files to be converted into it.
(v.in.arc can be used to convert ARC-INFO data from other mapsets as well, since the program searches for the specified input file names in the arc directories, if any exist, in the mapsets in the user's current mapset search path.)
Note: To use for text attributes, numeric fields with values >999 may contain no commas or TABs. Also, the first record must have all fields filled.
This program can be run either non-interactively or interactively. The program will run non-interactively if the user specifies the (optional) flag setting and needed parameter values on the command line, using the form:
Alternately, the user can type:
on the command line without program arguments; in this case, the program will prompt the user for the flag setting and parameter values in the manner shown below.
In ARC/INFO, three files are used to store polygon data:
These data files are described in further detail below, under the DATA FILE FORMATS section.
VECTOR (DIGIT) FILENAME Enter 'list' for a list of existing binary vector files Hit RETURN to cancel request >Next, the user is asked to specify the COVERAGE (feature) type to be imported into GRASS. Valid coverage types are polygon and line.
COVERAGE TYPE Enter "polygon" or "line" Hit RETURN to cancel request >IMPORTING A POLYGON COVERAGE
If the user chooses POLYGON coverage, he is asked if he wishes a neatline placed around his data. (The existence of neatlines in the output file can facilitate subsequent patching of data files.)
NEATLINE Do you want a neatline ? Enter "yes" or "no" >If the user types yes, vectors that box the data will be inserted into the GRASS vector output file (vector_out); otherwise, no neatline will be inserted into the output file.
Next, the user is prompted for the name of an existing lines-file containing the geographic coordinates of the arcs forming polygon perimeters. The lines-file is created with the ARC/INFO Ungenerate LINES option, and is in the same format at the prefix.pol file created by the v.out.arc program. The user sees the following prompt:
LINES FILENAME Enter name of the file created with the LINES option of the ARC/INFO Ungenerate command. Hit RETURN to cancel request >The next prompt for coverage type "polygon" asks for the name of an existing label-points file. The label-points file is created with the Ungenerate POINTS option, and is in the same format as the prefix.lab file created by the v.out.arc program. The user sees the following prompt:
LABEL-POINTS FILENAME Enter name of file created with the POINTS option of the ARC/INFO Ungenerate command. Hit RETURN if there is no such file >Finally, the program asks the user for the name of an existing label-text file. This file associates each label-point ID number with a text string. It is in the same format as the prefix.txt file created by the v.out.arc program.
LABEL-TEXT FILENAME Enter the name of a file that associates label-point ID numbers with text label strings Hit RETURN if there is no such file >v.in.arc then scans the label-text file to find the numbers of lines and columns, the column headers (if any), and the first three lines of actual data in the file. It displays this information to standard output to help the user determine which columns will hold the ID, Category value, and Attribute text data in the new vector output file. A sample of the program's output is shown below:
The LABEL-TEXT file has been scanned. There are 132 lines in the file and 8 columns in the file Column headers of the LABEL-TEXT file: rec#\ AREA PERIMETER SOILS#\ SOILS-ID SOIL-CODE DRAIN_CODE TXTUR-CODE Here are the first three lines : 1 -2.30228E+07 19399.848 1 0 0 0 0 2 81079.875 1678.826 2 1 15 3 3 3 955952.500 10229.637 3 2 19 8 8The column of category values must contain only integer values. The attribute text column can contain a floating point number, an integer, or a word (text string).
Finally, the user is prompted to enter line ID, category value, and attribute text column numbers.
Enter the number of the column that should be used for line IDs (probably the column with -ID) : Enter the number of the column that is to be used for GRASS category values: Enter the number of the column that should be used for GRASS attribute text:Once these column numbers have been entered, v.in.arc will begin converting the ARC/INFO "Generate" format files into GRASS vector file format.
IMPORTING A LINE COVERAGE
The user will also be prompted for input when importing ARC/INFO files containing linear features ("line coverage") data. Like polygon data, linear features are constructed by the series of arcs (aka, vectors) defining their perimeters. If the user selects LINE coverage, the prompts seen by the user will be different in two respects from those for POLYGON coverage. First, the user will not be asked whether or not a neatline is desired; and second, no label-points file name will be requested. In other respects, the treatment of LINE coverage is identical to that for POLYGON coverage.
The user is prompted for the name of the lines-file containing the geographic coordinates of these arcs. The lines-file must first have been created with the ARC/INFO Ungenerate LINES option, and is in the same format as the prefix.lin file created by the GRASS v.out.arc program.
LINES FILE, also known as prefix.lin or prefix.pol file.
This type of file can be created in ARC/INFO by using the lines subcommand of the Ungenerate command. Each line (aka, arc) is defined by a line-ID number, followed by a list of at least two easting and northing coordinate pairs, followed by a line with the word "END". The file is terminated with the word "END".
The line-ID number is important only for line coverage data. For a line coverage, the line-ID number is the number that associates each line with its attribute data.
3 711916.000000 4651803.000000 711351.875000 4651786.000000 END 3 709562.500000 4651731.000000 709617.250000 4651624.000000 709617.250000 4651567.000000 709585.000000 4651503.000000 709601.125000 4651470.000000 709696.875000 4651503.000000 709720.500000 4651574.000000 709823.750000 4651575.000000 709893.125000 4651741.000000 END 3 710296.875000 4651491.000000 710295.125000 4651470.000000 710223.000000 4651454.000000 710154.500000 4651463.000000 END END
LABEL-POINTS FILE, also known as prefix.lab file.
This type of file can be created in ARC/INFO using the Points option of the Ungenerate command. The first number on each line is a label-point ID number, and the following two numbers are (respectively) the easting and northing coordinate pair representing the geographic location of the label-point.
1 711539.875000 4651743.000000 2 711429.000000 4650632.000000 3 711027.625000 4651736.000000 4 711022.625000 4651519.000000 5 710482.750000 4651494.000000 6 710474.500000 4651667.000000 7 709269.750000 4651018.000000 8 709726.500000 4651604.000000 9 708926.375000 4651195.000000 10 708567.500000 4651644.000000 11 708272.750000 4651407.000000 ENDLABEL-TEXT FILE, also known as prefix.txt file.
The ARC/INFO Display command can be used to create this type of file.
1 -2.30228E+07 19399.848 1 0 0 0 2 81079.875 1678.826 2 1 15 3 3 955952.500 10229.637 3 2 19 8 4 41530.875 926.887 4 3 17 3 5 87900.188 1900.909 5 4 13 3 6 166125.125 3512.950 6 5 15 3 7 29460.563 824.968 7 6 17 3 8 1022769.875 9105.707 8 7 20 9 9 51385.500 1075.638 9 8 17 3 10 376834.875 4470.027 10 9 9 2 11 65802.688 1575.088 11 10 16 3
ARC/INFO data can be imported even if a label-points and/or a label-text file are missing; however, the lines and/or areas imported will not be labeled.
v.in.arc can handle label-text files both with and without header lines.