Book Image

Practical GIS

Book Image

Practical GIS

Overview of this book

The most commonly used GIS tools automate tasks that were historically done manually—compiling new maps by overlaying one on top of the other or physically cutting maps into pieces representing specific study areas, changing their projection, and getting meaningful results from the various layers by applying mathematical functions and operations. This book is an easy-to-follow guide to use the most matured open source GIS tools for these tasks. We’ll start by setting up the environment for the tools we use in the book. Then you will learn how to work with QGIS in order to generate useful spatial data. You will get to know the basics of queries, data management, and geoprocessing. After that, you will start to practice your knowledge on real-world examples. We will solve various types of geospatial analyses with various methods. We will start with basic GIS problems by imitating the work of an enthusiastic real estate agent, and continue with more advanced, but typical tasks by solving a decision problem. Finally, you will find out how to publish your data (and results) on the web. We will publish our data with QGIS Server and GeoServer, and create a basic web map with the API of the lightweight Leaflet web mapping library.
Table of Contents (22 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Dedication
Preface
14
Appendix

Spatial data on the web


In order to understand how spatial data on the web works, we first need to get a picture about the architecture of the web. The web resides on the Internet, where we have to deal with two kinds of software--servers and clients:

  • Server: An application that listens to a port with a background process (daemon), and accepts requests from that port. It processes valid requests and serves data according to them.
  • Client: An application responsible for sending valid requests to server side application(s) (for example, web browser-web server, SSH client-SSH server, QGIS-PostgreSQL). It also needs to be able to interpret the response sent back from the server.

Note

If you are familiar with the client-server architecture, you can skip the following subsection.

Understanding the basics of the web

The Internet is designed to be an infinitely expandable network of computers. Therefore, servers and clients are only the end points of this network--there are additional nodes doing other...