A decade ago, geo-spatial development was vastly more limited than it is today. Professional (and hugely expensive) Geographical Information Systems were the norm for working with and visualizing geo-spatial data. Open source tools, where they were available, were obscure and hard to use. What is more, everything ran on the desktop—the concept of working with geo-spatial data across the Internet was no more than a distant dream.
In 2005, Google released two products that completely changed the face of geo-spatial development: Google Maps and Google Earth made it possible for anyone with a web browser or a desktop computer to view and work with geo-spatial data. Instead of requiring expert knowledge and years of practice, even a four year-old could instantly view and manipulate interactive maps of the world.
Google's products are not perfect—the map projections are deliberately simplified, leading to errors and problems with displaying overlays; these products are only free for non-commercial use; and they include almost no ability to perform geo-spatial analysis. Despite these limitations, they have had a huge effect on the field of geo-spatial development. People became aware of what was possible, and the use of maps and their underlying geo-spatial data has become so prevalent that even cell phones now commonly include built-in mapping tools.
The Global Positioning System (GPS) has also had a major influence on geo-spatial development. Geo-spatial data for streets and other man-made and natural features used to be an expensive and tightly controlled resource, often created by scanning aerial photographs and then manually drawing an outline of a street or coastline over the top to digitize the required features. With the advent of cheap and readily-available portable GPS units, anyone who wishes to can now capture their own geo-spatial data. Indeed, many people have made a hobby of recording, editing, and improving the accuracy of street and topological data, which are then freely shared across the Internet. All this means that you're not limited to recording your own data, or purchasing data from a commercial organization; volunteered information is now often as accurate and useful as commercially-available data, and may well be suitable for your geo-spatial application.
The open source software movement has also had a major influence on geo-spatial development. Instead of relying on commercial toolsets, it is now possible to build complex geo-spatial applications entirely out of freely-available tools and libraries. Because the source code for these tools is often available, developers can improve and extend these toolkits, fixing problems and adding new features for the benefit of everyone. Tools such as PROJ.4, PostGIS, OGR, and Mapnik are all excellent geo-spatial toolkits that are benefactors of the open source movement. We will be making use of all these tools throughout this book.
As well as standalone tools and libraries, a number of geo-spatial-related Application Programming Interfaces (APIs) have become available. Google has provided a number of APIs that can be used to include maps and perform limited geo-spatial analysis within a website. Other services such as tinygeocoder.com and geoapi.com allow you to perform various geo-spatial tasks that would be difficult to do if you were limited to using your own data and programming resources.
As more and more geo-spatial data becomes available from an increasing number of sources, and as the number of tools and systems that can work with this data also increases, it has become essential to define standards for geo-spatial data. The Open Geospatial Consortium, often abbreviated to OGC (http://www.opengeospatial.org), is an international standards organization that aims to do precisely this: to provide a set of standard formats and protocols for sharing and storing geo-spatial data. These standards, including GML, KML, GeoRSS, WMS, WFS, and WCS, provide a shared "language" in which geo-spatial data can be expressed. Tools such as commercial and open source GIS systems, Google Earth, web-based APIs, and specialized geo-spatial toolkits such as OGR are all able to work with these standards. Indeed, an important aspect of a geo-spatial toolkit is the ability to understand and translate data between these various formats.
As GPS units have become more ubiquitous, it has become possible to record your location data as you are performing another task. Geolocation, the act of recording your location as you are doing something, is becoming increasingly common. The Twitter social networking service, for example, now allows you to record and display your current location as you enter a status update. As you approach your office, sophisticated To-do list software can now automatically hide any tasks that can't be done at that location. Your phone can also tell you which of your friends are nearby, and search results can be filtered to only show nearby businesses.
All of this is simply the continuation of a trend that started when GIS systems were housed on mainframe computers and operated by specialists who spent years learning about them. Geo-spatial data and applications have been democratized over the years, making them available in more places, to more people. What was possible only in a large organization can now be done by anyone using a handheld device. As technology continues to improve, and the tools become more powerful, this trend is sure to continue.