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What is the best way to transfer ArcInfo coverages?
There are several methods for copying ArcInfo coverages between two computers.
These methods depend on individual circumstances:
- Whether sending ArcInfo export (.e00) files, or a whole workspace
- Whether to, and how to, consolidate files together for delivery
- Whether to, and how to, compress the files
These choices are determined by:
- The number and arrangement of coverages
- The computer's operating systems (MS-DOS or UNIX)
- The transfer method (floppy disk, tape, or over a network)
I. Choosing between EXPORT files, or workspace:
ArcInfo EXPORT format, .e00, is the safest, most reliable way to copy ArcInfo coverages. An EXPORT format file is created by the EXPORT command, which places all the information in a coverage into one file. This includes any INFO tables that are associated with the coverage. ArcInfo looks for any INFO tables, in the same workspace as the coverage, that begin with the coverage's name and adds them to the .e00 file. For example, qbec_bc.pat is exported along with the coverage qbec_bc.
If the coverage is in single precision its export file can usually be imported into PC ARC/INFO, or ArcView2.
The export file has a '.e00' extension, and can be copied with UNIX cp, rcp, ftp, etc.
To export a coverage use the EXPORT command:
Arc: EXPORT COVER coverage_name filename FULL
The IMPORT command re-creates a coverage from the .e00 export file. For example, to import an export coverage into the $ARCLIB directory:
Arc: IMPORT COVER filename $ARCLIB/coverage_name
(The .e00 extension is not needed on the filename)
A WORKSPACE is the easiest way to transfer a collection of coverages that belong together between computers with the same operating system, i.e. UNIX or MS-DOS.
A workspace is the ArcInfo term for a disk directory which contains the files that make up a collection of coverages. There is one subdirectory for each coverage, plus an extra 'info' directory. To copy ALL the coverages in a workspace transfer the whole directory structure.
II. Consolidate for delivery
When transferring a UNIX workspace over the network, first use the UNIX .tar command to combine all the files in the workspace into one .tar file. This preserves the directory structure.
% cd workspace
% cd ..
% tar cvf workspace.tar workspace
To verify that the workspace.tar file was created properly, use the 'tv' option to list the files in it:
% tar tvf workspace.tar
III. Compress the files
Compression reduces the physical size of a file by storing its data more efficiently. It is recommended to use a compression utility program before storing or transferring files, and then uncompress them with a matching program before use. For instance, files compressed with PKZIP should be uncompressed with PKUNZIP.
When transferring data on floppies using PKZIP, the compression is built in. When transferring data on TAR (tape archive) tapes, compression is usually unnecessary since the tapes hold a lot of data.
Before transferring export or .tar files between UNIX computers over the network, reduce the size of the files with the UNIX compress command. Although the UNIX compress may not use the most efficient compression techniques, it is available on all UNIX computers.
To compress an export file:
% compress filename.e00
This replaces filename.e00 with filename.e00.Z
To compress a .tar file:
% compress filename.tar
This replaces filename.tar with filename.tar.Z
To restore a compressed, use 'uncompress':
% uncompress filename.e00.Z
IV. Copying files on floppies
To copy files between computers running MS-DOS, the simplest method may be to use 1.44 MB diskettes. The PKZIP utility is a simple way to copy a set of export files or workspaces onto a set of diskettes. It compresses the data as it writes it.
To copy a set of export files, place them in a directory and issue this DOS command:
C:> PKZIP -&w A:\DATA.ZIP *.e00
The '-&w' tells PKZIP to 'span disks' if the data won't fit on one disk.
To copy a complete workspace, go to the workspace and issue the DOS command:
C:> CD workspace
C:> CD ..
C:> PKZIP -r -&w A:\DATA.ZIP workspace
The '-r' tells PKZIP to preserve the directory structure of the workspace.
To verify that the data was copied properly, issue the DOS command:
C:> PKUNZIP -t A:\DATA.ZIP
PKUNZIP checks the data on the disk to verify that it is not corrupted.
V. Copying UNIX files on tape
To copy UNIX files on tape, use the UNIX 'tar' command. It copies a group of files or directory trees directly onto a tape with one command.
Place a tape in the tape drive, and use the UNIX 'mt' command to verify that the tape drive is hooked up properly:
% mt rewind
If this command issues an error, contact a system administrator.
Go to the directory containing the data and use the tar command with the 'c' option to copy the files directly onto the tape. To copy a set of export files from a directory:
% cd directory
% tar cv *.e00
To copy a complete workspace:
% cd workspace
% cd ..
% tar cv workspace
To confirm they copied properly, use the 'tv' option to list the files on the tape:
% tar tv
VI. Copying MS-DOS files to tape
Tape drives can be hooked up to the parallel port on a PC for backup and data transport purposes. These come with their own backup/restore utilities. Refer to the tape drive's manual for using such utilities.
Before using a tape drive to transfer data, it is important verify that the
recipient's device and software are compatible.
VII. Copying files with ftp
UNIX provides 'anonymous ftp' as a standard mechanism for transferring data over the Internet. To fetch files from another computer using ftp, follow these steps:
From UNIX, or DOS, enter the ftp command:
% ftp nodename
(for example ftp ssbux2.env.gov.bc.ca)
At the username: prompt, enter anonymous. At the password prompt, enter your UNIX username and hostname. For example: email@example.com. This logs the user on to nodename, with a very restricted set of privileges available to 'anonymous ftp' users. Use the cd command to navigate to the correct directory.
ftp> cd pub/directory
Use the ls command to make sure the files are there.
When fetching one or two files, use the get command to transfer the files.
ftp> get filename1
ftp> get filename2
When fetching several files, turn prompting off, and use the mget command to transfer the files.
ftp> prompt no
ftp> mget *.e00.Z
If sending files to another computer, use the put or mput command instead of the get above.
The above data was obtained from the British Columbia Ministry of Environment Web site