GMT

en/quickstart/gmt_quickstart.rst

@@ -1,7 +1,7 @@
-:Author: Hamish Bowman
-:Version: osgeo-live6.5
+:Author: Hamish Bowman, Massimo Di Stefano
+:Version: osgeo-live11.0
 :License: Creative Commons Attribution-ShareAlike 3.0 Unported  (CC BY-SA 3.0)
-:Copyright: 2011 by The OSGeo Foundation
+:Copyright: 2017 by The OSGeo Foundation
 
 .. image:: /images/project_logos/logo-GMT.png
   :scale: 100 %
@@ -18,22 +18,97 @@ Running
 
 
 Local documentation can be found in
-  `/usr/share/doc/gmt/html/ <../../gmt/html/index.html>`_,
-examples can be found in
-  `/usr/share/doc/gmt/examples <../../gmt/examples/>`_,
+  `/usr/share/doc/gmt/html/ <../../gmt/html/index.html>`_
+Examples can be found in
+  `/usr/share/doc/gmt/examples <../../gmt/examples/>`_
 
 
 .. packages:
   gmt-doc (and -pdf)
   gmt-coast-low
-  gmt-examples 
+  gmt-examples
   gmt-tutorial (and -pdf)
 
 
+Quick tutorial
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In this quick GMT tutorial we will use a digital terrain model (DTM) to generate a shaded relief map.
+
+As input dataset we will use a DTM from the GRASS GIS example dataset which is accessible by GDAL using the GDAL-GRASS diver.
+This will help in reducing the size footprint of data on the OSGeo-Live and demonstrate data interoperability between several formats.
+
+From a quick look at the DTM metadata using the GDAL command `gdalinfo`:
+
+::
+
+  gdalinfo /home/user/grassdata/nc_basic_spm_grass7/PERMANENT/cellhd/elevation
+
+
+we can see the DTM is in a projected coordinate system and the data range is between 50 and 160 meters.
+
+We can convert the DTM in a GMT Compatible netCDF file format with `gdal_translate` as follow:
+
+::
+
+  gdal_translate -of GMT /home/user/grassdata/nc_basic_spm_grass7/PERMANENT/cellhd/elevation elevation.gmt
+
+For our GMT example we will first transform the dataset into geographic coordinates Longitude-Latitude (EPSG:4326) using the `gdalwarp` command:
+
+::
+
+  gdalwarp elevation.gmt geo_elevation.gmt -t_srs EPSG:4326
+
+
+To assign a color map to our grid we can make a GMT color palette tables
+with the `makecpt` command. We will set the range and number of colors with the flag `-T`
+and assign a colormap with the flag `-C`.
+
+::
+
+  gmt makecpt -Chaxby -T50/160/10 -Z > elevation.cpt
+
+
+You can experiment with other colortables, see `man gmt makecpt` for a complete list.
+
+For our shaded relief example we need to specify how the color intensity is distributed along the grid.
+To do so, we will compute the directional derivative, or gradient, from our grid using the `grdgradient` command.
+In `grdgradient` we will use the `-Ne` flag to normalize the output using a cumulative Laplace distribution and the `-A` flag Azimuthal direction for a directional derivative.
+
+::
+
+  gmt grdgradient geo_elevation.gmt -Ne0.8 -A100 -fg -Ggradient.nc
+
+The output is a netCDF file which can then be used as color intesity by the `grdimage` command as follow:
+
+::
+
+  gmt grdimage geo_elevation.gmt -Igradient.nc -JM6i -P -Ba -Celevation.cpt -K > GMT_tut_OSGeo-Live.ps
+
+
+Finally we can add a colorbar with `psscale`:
+
+::
+
+  gmt psscale -DjTC+w5i/0.25i+h+o0/-1i -Rgeo_elevation.gmt -J -Celevation.cpt -I0.4 -By+lm -O >> GMT_tut_OSGeo-Live.ps
+
+
+Here the flag `-D` is used to select the colorbar position `TC: Top Center`, the size `5x0.25` expressed in inches `i` the orientation by `h: horizontal`
+and the flag `-By` to set a label `m` on the `y axis`.
+
+The output ps document should look like:
+
+.. image:: /images/screenshots/800x600/GMT_tut_OSGeo-Live.png
+  :scale: 100 %
+  :alt: North Caroline - sample elevation data
+  :align: center
+
+
 Examples
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-There are 30 example jobs built in:
+To explore the GMT potential we strongly suggest to go trough the GMT tutorial and follow the several examples available in the src code.
+There are 30 example jobs built in, to test:
 
 Open a terminal, then