	@(#)README.dbase	1.10  06/21/99

README for gmt/src/dbase directory.

==> CHANGES IN GMT 3.3.1 <==

We have added more flexibility in dealing with the fact that
binary files written on one system may need to be byte-swapped
on another.  For instance, native binary files written on a
Sun or Mac will have Bigendian byte order, while the same file
written on a machine with Intel or Alpha chips will be Little-endian.
Since some users mount Sun disks with PC-NSF and want to read
the same binary files with grdraster from both PCs and Suns, a
problem can arise.  The new grdraster implements a new polify
to deals with this situation:

   1. When grdraster is compiled, it "remembers" what byteorder
      the machine it is running on supports (L or B).
   2. Files given in grdraster.info are ASSUMED to be of the same
      byteorder, UNLESS the grdraster.info record has an extra
      column with the 1-character byteorder flag L or B.  Thus,
      if a particular binary file was generated on a Sun you should
      add the flag B.  That way, should you every copy the file (and
      the grdraster.info file to a machine with another byteorder
      it will read properly.

==> CHANGES IN GMT 3.3 <==

The makefile have an option to build-in automatic swapping
of input data.  Because the input data sets can come from
many different sources it may be more useful to instead
swap those data sets that were created on machines with a
different byte-order than yours.  To do so, simply use

xyz2grd troublefile -Sgoodfile -V -Z?

where troublefile is the file with byte-order problems
      goodfile is the name of the fixed file
      ? is one of h (short), H (unsigned short), i (int)
	I (unsigned int), l (long), f (float), d (double)

==> CHANGES IN GMT 3.2 <==

Default GMT_GRIDDIR directory is now $GMTHOME/lib/dbase
following the new policy for supplemental programs and
their support files.

==> CHANGES IN GMT 3.1 <==

With the release of GMT 3.1, several supplemental dbase programs
became obsolete due to the inproved flexibility of xyz2grd; these
are no longer distributed in the GMT3.1 supplemental archive.
Specifically:

raster_transpose.c:  Program was used to read a global 5'x5' file
	of signed short integers written as columns from W to E
	with each column written fron N to S and write out a
	scanline oriented file.  Its function can be duplicated by

	xyz2grd -R0/359:55/-90/90 -I5m -ZLTh oldfile -Gtmp.grd
	grd2xyz tmp.grd -ZTLh -bo > newfile

ngdc/etopo5_append.c:  Program to add one row of values to the ETOPO5.dat
	file from NGDC's "Global Relief" CD-ROM which is missing the
	south pole. Its function can be duplicated with

	xyz2grd -R0/359:55/-90/90 -I5m -ZTLh -N2810 etopo5.dat -Gtmp.grd
	grd2xyz tmp.grd -ZTLh -bo > new_etopo5.dat

ngdc/haxby_trim.c:  Program to take the file haxby.bin from the NGDC CD-ROM
	"Global Relief" and trim off the zero rows outside +/- 72 degrees
	latitude, to save disk space.  Its function can be duplicated with

	xyz2grd -R0:05/360/-71:55/72 -I5m -ZTLhxs1866240 haxby.bin -Gtmp.grd
	grd2xyz tmp.grd -ZTLh -bo > new_haxby.bin

	where 1866240 is 216 rows of 4320 values at 2 bytes each.  These
	steps also allows for the fact that first row is at 0 degrees 5 min
	east.

sio/siofligage.c:  Program to read the global gridded age file by
	Dietmar Muller et al., as supplied by ftp from Scrippts,
	with 10 wsamples per degree grid registered in -R0/360/-72/72
	and flip it over since it was written in upside-down scan-line
	format (Australian view?).  Later versions of these data are no
	longer upside down.

	xyz2grd -R0/360/-72/72 -I6m -ZBLh infilename -Gtmp.grd
	grd2xyz tmp.grd -ZTLh -bo > outfilename

For any of these examples, you may append w to the -Z options to swap byte-
order on systems that are not bigendian.


Do install the only supplied program, grdraster, simply type

make install

the process inherits all your makefile settings from the main GMT src
directory.
grdraster will look for the file grdraster.info and all the files referred
to in it (unless filename starts at /) in the directory indicated by the
environmental variable GMT_GRIDDIR.  If this is not set, grdraster will
default to $GMTHOME/lib.
You may copy the manl/grdraster.man page to /usr/man/manl if you wish.

==> GMT 3.0 COMMENTS <==

Programs are supplied which allow the user to extract grd files spanning
user-defined regions [-R option] from large-area native binary data files.
Information is also supplied to help you set up a database from existing
files available on CD or through ftp over Internet.  The data files we
describe here may be of interest only to Earth scientists.  However, other
GMT users may want to play with these anyway, to see how to adapt the
program "grdraster" to their needs.

A sub-directory "ngdc" is supplied with programs designed to aid
the user in taking files from a CD-ROM called "Global Relief" and setting
up a database used by a new version of "grdraster".  This CD is available
from the U. S. National Geophysical Data Center (mosaic:  http://www.ngdc.
noaa.gov   gopher:  gopher.ngdc.noaa.gov   ftp:   ftp.ngdc.noaa.gov
general info   info@ngdc.noaa.gov   point of contact Robin R. Warnken
rrw@mail.ngdc.noaa.gov)  The files on this CD which we support here have
gravity anomalies and topographic elevations.

Another sub-directory, "sio" is supplied with programs designed to
aid the user in taking files from an ftp site at the Scripps Institution
of Oceanography and plugging these into "grdraster" or otherwise into GMT.
The file that plugs into grdraster contains ages of the sea floor determined
from magnetic anomaly data.  There is also a file of gravity anomalies which
is supplied in a mercator projection, and programs "img2latlongrd" and
"img2mercgrid" are provided to handle that.


PLEASE NOTE that the authors of GMT cannot supply you with these data files.
You have to ftp the files yourself, or purchase the CD.  We are giving you
these software tools as a courtesy and to encourage you to explore what data
products are out there in cyberspace and at the world data centers.  We are
not responsible for the quality of these data sets.  We did not create them
(except in a couple of cases !) and they are not ours to give away.  GMT is
a system of software tools.  It is not a database.


HISTORY and CHANGES in version 3.0:

In the past, we have supplied a program "grdraster" which extracted grd files
spanning regions specified by -R<w>/<e>/<s>/<n> from native binary grid files.
The supplied version of grdraster.c read global files sampled at 5 minutes of
latitude and longitude and written from W to E as a sequence of 2161 element
column vectors.  This was a file format used at Lamont, and Paul Wessel has
used it at Hawaii.

Meanwhile, at Scripps and later at NOAA, Walter Smith was using a different
"grdraster" which read native binary files in "scan-line format", that is,
written from N to S as row vectors, with each row written from W to E.  The
Smith version supported different registrations (grid or pixel), and varying
sampling intervals, etc. so was more flexible.  Also, the various data sets
available on CD and by ftp are usually written in scan-line format, so in
version 3.0 we now supply this version.

In previous releases of GMT, we have supplied the source code for Paul's
version and called it "grdraster_gmt.c".  This was so that in extracting
the tar file, it would not clobber whatever the user had named "grdraster.c".
This release only supports the new version; users who installed files that
could be read by the old version should convert their files (see below).

If you have something set up which you like, don't change it.  Ignore these
files.  If you want to use the new system, we suggest you use the 3.0
version.  If you have the old (Paul's) system but want to go to the new
system, the program "raster_transpose" will let you flip your old data
files to make them compatible with the new 3.0 version of grdraster.

Actually, with user-defined binary I/O available in GMT 3.0, grdraster is
not really needed.  All that is needed is to have a header on each file.
But this is what we have working for now, and we supply it to be helpful
to other users of this data.


TO USE THIS VERSION:

First, create a directory where you have "enough" disk space for the
files which grdraster will read.  The size of "enough" depends on how
much data you want to use.  For example, the world topography data called
"etopo5" which is on the NGDC "Global Relief" CD-ROM takes about 19 Mbytes.
Walter Smith's installation has lots of data files he has taken from
internet, and uses about 480 Mbytes.

Now edit the macro GRIDDIR in the makefile and set it to the complete
path name (starting with "/") of the directory you created.  Also,
edit switches having to do with cc, install, etc. as you do when you
install GMT.

Now you can make all; make install; make clean; in this (dbase)
directory.  (This assumes that you have already made GMT.)  This will make
the programs grdraster and "raster_transpose".  raster_transpose will
convert files in Paul's old grdraster format to the new grdraster format.
If you don't need this you can delete it from the GMTBIN dir now.

Now take the file called "documentation" which is in this directory
and move it to the GRIDDIR.  The file as supplied has entries for several
data files.  "documentation" should have one line for each file you
install in the GRIDDIR.  The file we supply here is a sample.  You can
comment out the lines you do not need by placing a "#" as the first
character on a line.  If you add grids you get from other sources
(or which you had and converted using "raster_transpose"), you can add
an entry for these to the file.  It should be obvious from the file
how to do this (we hope!).

Scripps data:

At Scripps you can get two kinds of data:  A worldwide sea floor age
map based on magnetic anomaly identifications, and a world wide marine
gravity map based on satellite altimetry.  The ages are ready to plug
into grdraster except that they need to be flipped over (they are
written from S to N instead of the other way around).  The gravity map
is harder to use because it is gridded in a Mercator-projected 
coordinate system instead of the the lat,lon system.  Programs are
supplied in the "sio" subdirectory to deal with these files.  If you
want these, edit the make file and make all,install,clean as before.

To take files from Scripps:  use anonymous ftp from baltica.ucsd.edu
(132.239.121.193) and get the files you want.  If you want seafloor age
data, cd to "pub/global_age" and get (binary mode) a file called
"globalage.bint".  Then use "dd" if you need to swap bytes on this file
(it is big-endian) and run "sioflipage" to flip it, putting the result
in your GRIDDIR.  If you want the marine gravity field, cd to "pub/
global_grav" and get (binary mode) "world_grav.img.4".  Because of the
Mercator projection of this file, it is not read by grdraster but we
supply programs "img2mercgrd" and "img2latlongrd" to handle it directly.
To make other plots overlay this data, you must use the Sphere as your
default ellipsoid.  Also note that the world_grav.img file is updated
as more data become available.  At this writing (January 1995) the current
version is ".4".  This file also has information about satellite tracks
encoded into it, which is another reason it cannot be handled with a
simple grdraster or grd header.

NGDC data:

To take files from the "Global Relief" CD-ROM:  Some files will come
over directly.  The file called "topo/usgs/topo30." contains elevations
in feet above and below sea level (or lake level datum) for the 48 state
area of the U.S. and near-offshore.  This file is in big-endian byte
order so either copy it or use "dd" to swap the bytes if you want this
one.  Put your copy in your GRIDDIR.  The files in gravity/geosat called
"GEOSAT30.BIN" and "GEOSAT30.DOS" are in big-endian and little-endian
byte order and are gravity fields over the ocean areas between 30 S
and 72 S latitude.  Copy the one which is appropriate for your system
to your GRIDDIR if you want this data.  Software in the ngdc
directory will help you take the files "gravity/seasat/haxby.bin" and
"topo/etopo5/etopo5.dat (or dos)" and fix them up for installation in
your GRIDDIR.  etopo5 needs the south pole added (done by the program
etopo5_append) and haxby.bin needs empty rows between 72 and 90 lat
trimmed off [and optional byte swapping] (done by haxby_trim).  So again
you can edit the makefile, then run these programs to make the versions
for the GRIDDIR.

Remember:

You need to comment out lines in "documentation" if you are not using
the corresponding files.  Also, the programs "haxby_trim, etopo5_append",
raster_transpose", "sioflipage" only need to be used once, so you don't
really need to leave them installed in the GMTBIN directory.  You might
as well delete them when you are finished with them, to save space.  The
only files that need to live in your directory are grdraster and if you
use the SIO gravity file:  img2latlongrd and img2mercgrid.

NOTE:  Whenever you take files from people, whether on CD from a data center
or by ftp from Internet, be sure to also take the documentation, print it out,
and read it.  And figure out how to give credit where it is due.  When you
publish results using other people's data, cite their article or data
distribution as appropriate.  They have been generous to you in giving
away their data; don't let them perish.

