Example A4: Topographic maps
        
                                 

Steps to create a topographic map and add more features on it:


1). logon to the Linux computer 
2). make a new directory.
3). cd to this new directory
    (Note: if you failed to do steps 2 and 3, your existing
	plot.gmt file in the directory where you are going to work, 
	will be erased).
4). topoimag  (and input the required parameters)
5). pico plot.gmt and add an '-K' in the line:

    pscoast -R -JM -Df -W2 -Na/1 -O -V >>tmp.ps 

6). add more features to the map using "pstext", "psxy" etc.
	See steps 2-8 of  Example A3  for references.

7). type plot.gmt to execute the GMT commands.


Explanations:


Topographic data sets are in GRD (stands for grid) format.
At this stage, we have installed the following data sets on r42sgao:

etopo5: covers all the globe (land and ocean). The space between
	sampling points (i.e., the resolution) is 5 arc-minutes, which 
	is about 10 km.
	This data base is good for plotting large maps (e.g. the
	entire U.S. or bigger). For smaller maps, the resolution
	might be too low and the results are not pretty enough.

topo2min: covers all the globe except for the areas north of 72N
	and south of 72S. The resolution is 2 arc-minutes, which
	is about 3 km.

gtopo30: covers the land area of the world only except for the 
	areas north of 72N and south of 72S. The resolution is 0.5 
	arc-minutes, which is about 1 km.

dem1: covers the United States. The resolution is 0.05 arc-minutes,
	which is about 0.1 km. The problem is that the file is
	too large (several gigabytes) so we had to split it into
	several patches named block1m.grd, block2m.grd etc ...

As you can see it, it is difficult to determine which file to use
	and where to find them on the disks. To solve this problem,
	Dr. Kelly Liu wrote a FORTRAN program named topoimag to
	automatically create a GMT code for you, based on your input.
	It determines the most proper topographic file to use and
	for the dem1 case, judge the right patch to use.

Note: For the dem1 (the highest resolution data set), some areas 
	have no data. Also, if your area covers the boundary
	between two patches, you may be in trouble. Talk to S.Gao
	or Kelly Liu if your area of interest happens to be in
	the trouble-some areas.