Graphics Programs Reference
In-Depth Information
'MapLonLimit',[40 50], ...
'Frame','on', ...
'MeridianLabel','on', ...
'ParallelLabel','on');
plotm(data(:,2),data(:,1),'k');
Note that the input for
plotm
is given in the order
longitude
, followed by the
latitude
. The second column of the data matrix is entered fi rst. In contrast,
the function
plot
requires an
xy
input. The fi rst column is entered fi rst. The
function
axesm
defi nes the map axis and sets various map properties such
as the map projection, the map limits and the axis labels.
7.3 The 2-Minute Gridded Global Elevation Data ETOPO2
ETOPO2 is a global data base of topography and bathymetry on a regular
2-minute grid. It is a compilation of data from a variety of sources. It can be
downloaded from the US National Geophysical Data Center (NGDC) web
page
http://www.ngdc.noaa.gov/mgg/fliers/01mgg04.html
From the menu bar
Free online
we select
Make custom grids
which is linked
to the
GEODAS Grid Translator
. First we choose a Grid ID (e.g.,
grid01
), the
Grid Data Base (e.g.,
ETOPO2 2-minute Global Relief
), our computer sys-
tem (e.g.,
Macintosh
) and the Grid Format (e.g.,
ASCII
for both the data and
the header). Next we defi ne the
longitude
and
latitude
bounds. For example,
the latitude (
lat
) from -20 to +20 degrees and a longitude (
lon
) between +30
and +60 degrees corresponds to the East African coast. The selected area can
be transformed into a digital elevation matrix by pressing
Design-a-grid
.
this matrix may be downloaded from the web page by pressing
Download
your Grid Data
,
Compress and Retrieve
and
Retrieve compressed fi le
in the
subsequent windows. Decompressing the fi le
grid01.tgz
creates a directory
grid01_data
. This directory contains various data and help fi les. The sub-
directory
grid01
contains the ASCII raster grid fi le
grid01.asc
that have the
following content:
NCOLS 901
NROWS 1201
XLLCORNER 30.00000
YLLCORNER -20.00000
CELLSIZE 0.03333333
NODATA_VALUE -32768
270 294 278 273 262 248 251 236 228 223 ...
280 278 278 264 254 253 240 234 225 205 ...