New global shorelines database

[Simon Cox]

As some of you may already be aware, a new
"global self-consistent hierarchical high-resolution shorelines" (gshhs)
database has been prepared by Paul Wessel (SOEST, Hawaii) and Walter Smith
(NOAA)
- the guys who wrote GMT.
This can be obtained by ftp from
ftp://ftp.ngdc.noaa.gov/MGG/shorelines/  , mirrored at
ftp://kiawe.soest.hawaii.edu/pub/wessel/gshhs/ .
The original source of the data is the CIA digitised data.
This has also been decimated to four lower resolutions using a
Douglas-Puecker algorithm, modified to remove anomalous line crossings.
Full explanations are available in the ftp directories, with some code to
manipulate it.
I downloaded the data and have found it to be superior to data
that I previously got from NOAA's "global relief data" CD-ROM.

We have written a C program **gshhstograss** which extracts a
rectangular area of the data and writes a grass dig_ascii format file
which may then be imported into a grass database using v.in.ascii.
This program is available from the soest site now, and should soon
be available at noaa as well.  It does not use any Grass programming
libraries so should be installable easily by anyone.  The usage of the
program is given.

Note that the data is in geographic (long-lat) coordinates, and the
complete "full" resolution binary data file is ~90 MB uncompressed.
Since my method uses ascii files as intermediate these may be larger still,
though I would recommend only converting the area that you are interested in.
Importing using v.in.ascii goes smoothly, though v.support (v.build) can
take a loooooong time to run.

DEC Alpha users note:
you must set the flag -DFLIP when compiling any of the C programs supplied
to read the data.

Enjoy                                   Simon Cox


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Dr Simon Cox                        __  \
CSIRO Exploration & Mining       ,~'  L_|\    Australian
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