GDAL Python samples on osgeo.org

http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/

Tutorial

This tutorial is titled “Create beautiful hillshade maps from digital elevation models with GDAL and Mapnik” and is from 2011.

http://www.mikejcorey.com/wordpress/2011/02/05/tutorial-create-beautiful-hillshade-maps-from-digital-elevation-models-with-gdal-and-mapnik/

This tutorial provides you with all the data you need to create a hill-shade image.

Course

This is the course material for a GIS course at Utah State University. The course was titled “Geoprocessing with Python using Open Source GIS”.

http://www.gis.usu.edu/~chrisg/python/

This is a course homepage, and there is a zip-file that contains data and samples.

Another collection of GDAL tutorials

http://www.cartotalk.com/index.php?showtopic=5144

You have a CSV file called “data.csv”. It has a header line, and is delimited using “;”. You want to import it into Postgres and a table called “your_table”:

Create the database table. Set column-types so the string fields in the CSV file, can be cast to values in columns.

CREATE TABLE your_table
(
  -- Your columns
);

Execute COPY command:

COPY your_table FROM '/path/to/csv/file/data.csv' WITH DELIMITER ';' CSV HEADER;

If the data is geospatial

Another option is using ogr2ogr, which has a CSV driver. The COPY command could be faster.

If you have point data, check out this howto: Loading Point Data from a CSV File into PostGIS

Using bottles of water (with different waterlevels) and a vibration sensor on each, one could make a low tech thing that detects whether a male or female is speaking in the room. Why not use a microphone and a spectrum analyzer? Well, because you are McGyver and you’re caught in some prison, and mission dictates that you find out when the guy with the really bassy voice enters the room. You know, ad hoc spy stuff.

Here is a figure that illustrates the “Low Tech Male/Female Voice Detection System”:

The following template is adapted from the annotated 3d box example.

% Template for drawing with tikz 3D package
\documentclass[]{article}
\usepackage{tikz}
\usetikzlibrary{3d}
 
\begin{document}
 
% Draw a 3D coordinate system
 
\begin{center}
\begin{tikzpicture}[x  = {(1cm,0cm)},
                    y  = {(0.4cm,0.6cm)},
                    z  = {(0cm,1cm)},
                    scale = 1,
                    color = {lightgray}]
 
\begin{scope}[canvas is xy plane at z=0]
  % x-axis
  \draw[blue,->] (0,0) -- (5,0) node (x-axis) [right] {$x$};
  % y-axis
  \draw[red,->] (0,0) -- (0,5) node (y-axis) [above] {$y$};
\end{scope}
 
\begin{scope}[canvas is yz plane at x=0]
  % z-axis
  \draw[green,->] (0,0) -- (0,5) node (z-axis) [above] {$z$};
\end{scope}
 
\end{tikzpicture}
\end{center}
\end{document}

The code is almost self-explanatory, but here is the explanation. You can draw in either the xy plane (for z=something), the xz plane (for y=something) or the yz plane (for x=something). If all you want to do is draw in these planes, then the above template is a good place to start. It draws a coordinate system.

The x, y and z values in the following snippet, defines the directions of the x, y and z axis, when projected onto your computer screen. Play around with the values and see what happens if you don’t get it right away:

\begin{tikzpicture}[x  = {(1cm,0cm)},
                    y  = {(0.4cm,0.6cm)},
                    z  = {(0cm,1cm)},

You pick the plane you want to draw in. To draw in the yz plane where it intersects the x-axis at x=0, do the following:

\begin{scope}[canvas is yz plane at x=0]

My university only has a subscription with ACM, not with IEEE, so it’s free (for me) to read an ACM paper, while I have to pay to read or even download a citation of an IEEE paper. When I asked the faculty why we don’t have an IEEE subscription, the answer was: Because it is really expensive. So what kind of papers do you think I’m looking at the most?

This makes me think: Will there eventually be a strong skew in the kinds of paper I’ll end up citing? Many citations of ACM papers, none or few of IEEE papers? For now the answer is a definite yes. When I’m snowballing on a keyword, I now tend to close browser tabs with IEEE papers more often than ACM papers.

I have no doubts. This is a problem for science!

Using shp2pgsql

shp2pgsql myshapefile -I xyz.mytable > statements.sql
psql -d mydb -h localhost -U dbuser -f statements.sql

This tip and many more can be read in Making Maps Fast.

Using ogr2ogr

This is even easier with ogr2ogr:

ogr2ogr -f "PostgreSQL" PG:"host=localhost user=dbuser dbname=mydb password=secret" -lco SCHEMA=xyz myshapefile.shp

PGF/TikZ is a tandem of languages for producing vector graphics from a geometric/algebraic description. You can use this language inside tex files, to programmatically draw nice 2D and 3D graphics. Another package which some people prefer for 3D is asymptote.

Read the manual.

Tutorials for tikZ

For more information read one of the tutorials and the tikz resources page, which includes helpful tools etc.

There are tutorial videos online like this video. There are also tutorials on youtube like the following, but this does not cover 3D graphics unfortunately:

To learn how to make 3D stuff, start by looking at the examples below. If you can make sense of it…

tikZ 3D examples

Look at the 3D tikz example page for more 3D examples.

	[TEX]
	[TEX]

Choose the appropriate sourcecode version by going to http://nodejs.org/#download.

wget http://nodejs.org/dist/v0.6.7/node-v0.6.7.tar.gz # or use curl

Install g++

I found that the g++ is needed to install node.js from sourcecode. Found a hint about installing g++ on Amazon Linux, which basically tells you to do this:

sudo yum install gcc-c++.x86_64

Install openssl

To get ssl support, you need to install openssl-devel.x86_64 which is not installed by default (only binary version). Alternately you can install without ssl support with ./configure –without-ssl. (thanks to my colleague Elias Löfgren for helping out here)

sudo yum install openssl-devel.x86_64

Install make

(thanks Daniel for pointing this out)

sudo yum install -y make.x86_64

Install Node.js

Now you can configure, make, install:

./configure
make
make install

check_helloworld.py:

#!/usr/bin/env python
 
# optparse is Python 2.3 - 2.6, deprecated in 2.7
# For 2.7+ use http://docs.python.org/library/argparse.html#module-argparse
from optparse import OptionParser
 
# CONSTANTS FOR RETURN CODES UNDERSTOOD BY NAGIOS
# Exit statuses recognized by Nagios
UNKNOWN = -1
OK = 0
WARNING = 1
CRITICAL = 2
 
# TEMPLATE FOR READING PARAMETERS FROM COMMANDLINE
parser = OptionParser()
parser.add_option("-m", "--message", dest="message", 
   default='Hello world', help="A message to print after OK - ")
(options, args) = parser.parse_args()
 
# RETURN OUTPUT TO NAGIOS
# USING THE EXAMPLE -m PARAMETER PARSED FROM COMMANDLINE
print 'OK - %s' % (options.message)
raise SystemExit, OK

Define a command that uses this plugin:

define command {
    command_name    check_hello_world
    command_line    $USER1$/check_hello_world.py -m 'some message'
}

Check a host or service using the command:

define service {
    use         generic-service
    host_name           some-host
    service_description Check using the hello world plugin (always returns OK)
    check_command       check_hello_world
}

say 'hello world'

Which will make your computer talk. To save the audio output to a file, use the -o option. A full example is:

say -o hello.aiff -v 'Alex' 'Hello, my name is Alex'
open hello.aiff

This will say ‘Hello, my name is Alex’, in the voice of ‘Alex’ (other voice-options are ‘Bruce’, ‘Fred, ‘Kathy’, ‘Vicki’ and ‘Victoria’), and save the output to ‘hello.aiff’.

It seems there is no option for setting the speed (can be set in System preferences -> speech). See man say for all options. Interesting options include sending the output over the network.