Open Source GIS (Geographic Information Systems) is a growing area with the explosion of Google Maps-based websites and spatially-aware devices and applications. The GIS market is growing rapidly, and as a Python developer you can't afford to be left behind. In today's location-aware world, all commercial Python developers can benefit from an understanding of GIS concepts and development techniques.
Working with geo-spatial data can get complicated because you are dealing with mathematical models of the Earth's surface. Since Python is a powerful programming language with high-level toolkits, it is well-suited to GIS development. This book will familiarize you with the Python tools required for geo-spatial development. It introduces GIS at the basic level with a clear, detailed walkthrough of the key GIS concepts such as location, distance, units, projections, datums, and GIS data formats. We then examine a number of Python libraries and combine these with geo-spatial data to accomplish a variety of tasks. The book provides an in-depth look at the concept of storing spatial data in a database and how you can use spatial databases as tools to solve a variety of geo-spatial problems.
It goes into the details of generating maps using the Mapnik map-rendering toolkit, and helps you to build a sophisticated web-based geo-spatial map editing application using GeoDjango, Mapnik, and PostGIS. By the end of the book, you will be able to integrate spatial features into your applications and build a complete mapping application from scratch.
This book is a hands-on tutorial, teaching you how to access, manipulate, and display geo-spatial data efficiently using a range of Python tools for GIS development.
Chapter 1, Geo-Spatial Development Using Python, introduces the Python programming language and the main concepts behind geo-spatial development
Chapter 2, GIS, discusses many of the core concepts that underlie GIS development. It examines the common GIS data formats, and gets our hands dirty exploring U.S. state maps downloaded from the U.S. Census Bureau website
Chapter 3, Python Libraries for Geo‑Spatial Development, looks at a number of important libraries for developing geo-spatial applications using Python
Chapter 4, Sources of Geo-Spatial Data, covers a number of sources of freely-available geo-spatial data. It helps you to obtain map data, images, elevations, and place names for use in your geo-spatial applications
Chapter 5, Working with Geo-Spatial Data in Python, deals with various techniques for using OGR, GDAL, Shapely, and pyproj within Python programs to solve real-world problems
Chapter 6, GIS in the Database, takes an in-depth look at the concept of storing spatial data in a database, and examines three of the principal open source spatial databases
Chapter 7, Working with Spatial Data, guides us to implement, test, and make improvements to a simple web-based application named DISTAL. This application displays shorelines, towns, and lakes within a given radius of a starting point. We will use this application as the impetus for exploring a number of important concepts within geo-spatial application development
Chapter 8, Using Python and Mapnik to Generate Maps, helps us to explore the Mapnik map-generation toolkit in depth
Chapter 9, Web Frameworks for Python Geo-Spatial Development, discusses the geo-spatial web development landscape, examining the major concepts behind geo-spatial web application development, some of the main open protocols used by geo-spatial web applications, and a number of Python-based tools for implementing geo-spatial applications that run over the Internet
Chapter 10, Putting it all Together: a Complete Mapping Application, along with the final two chapters, brings together all the topics discussed in previous chapters to implement a sophisticated web-based mapping application called ShapeEditor
Chapter 11, ShapeEditor: Implementing List View, Import, and Export, continues with implementation of the ShapeEditor by adding a "list" view showing the imported Shapefiles, along with the ability to import and export Shapefiles
Chapter 12, ShapeEditor: Selecting and Editing Features, adds map-based editing and feature selection capabilities, completing the implementation of the ShapeEditor application
To follow through the various examples, you will need to download and install the following software:
Python version 2.x (minimum version 2.5)
GDAL/OGR version 1.7.1 or later
GEOS version 3.2.2 or later
Shapely version 1.2 or later
Proj version 4.7 or later
pyprojversion 1.8.6 or laterMySQL version 5.1 or later
MySQLdb version 1.2 or later
SpatiaLite version 2.3 or later
pysqliteversion 2.6 or laterPostgreSQL version 8.4 or later
PostGIS version 1.5.1 or later
psycopg2version 2.2.1 or laterMapnik version 0.7.1 or later
Django version 1.2 or later
With the exception of Python itself, the procedure for downloading, installing, and using all of these tools is covered in the relevant chapters of this book.
This book is useful for Python developers who want to get up to speed with open source GIS in order to build GIS applications or integrate geo-spatial features into their applications.
In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.
Code words in text are shown as follows: "We can then convert these to Shapely geometric objects using the shapely.wkt module."
A block of code is set as follows:
import osgeo.ogr
shapefile = osgeo.ogr.Open("TM_WORLD_BORDERS-0.3.shp")
layer = shapefile.GetLayer(0)When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:
from pysqlite2 import dbapi as sqlite
conn = sqlite.connect("...")
conn.enable_load_extension(True)
conn.execute('SELECT load_extension("libspatialite-2.dll")')
curs = conn.cursor()Any command-line input or output is written as follows:
>>> import sqlite3 >>> conn = sqlite3.connect(":memory:") >>> conn.enable_load_extension(True)
New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "If you want, you can change the format of the downloaded data by clicking on the Modify Data Request hyperlink".
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