The Tile-Based Mapping Transition in Cartography - Maps for the Future Children Education and Internet - page 159

interaction with the application. AJAX has transformed the online client/server
experience and is used by many different types of applications.
13.3.3 Mashups and the Application Programmer Interface
Mashups are an integral part of what is commonly referred to as Web 2.0 (Batty
et al. 2010 ). Beginning in about 2004, Web 2.0 represents a variety of innovative
resources, and ways of interacting with, or combining web content. In addition to
mashups, Web 2.0 also includes the concept of wikis, such as Wikipedia, blog
pages, podcasts, RSS feeds, and AJAX. Social networking sites like MySpace and
Facebook are also seen as Web 2.0 applications.
Central to mashups are Application Programming Interfaces (APIs), online
libraries of functions that that are made freely available. Many different API
libraries have been written for the user-driven web. APIs are the tools that facilitate
the melding of data and resources from multiple web resources by providing tools
to acquire, manipulate and display information from a variety of sources. In a strict
sense, map mashups combine data from one website and display it with a mapping
API. The term has come to be used for any mapping of data using an API, even data
supplied by the user.
APIs are used for many different types of applications but the creation of maps is
one of the major uses. This should not be surprising because there is a great deal of
data that has a location component. The relative ease of overlaying all types of
information with online mapping tools has further transformed cartography from a
passive to an active enterprise with all types of data being mapped.
Introduced in 2006, the Google Maps API consists of a series of map-related
functions. These functions control the appearance of the map, including the scale,
position, and any added information in the form of points, lines or areas. The
purpose of the API is to make it possible to incorporate user-defined maps on
websites, and to overlay information from other sources.
13.3.4 Map Layers
Google and the other online map providers have a large number of pre-defined
layers. These layers have also been tiled—like all of the tiles that make up the map
and the satellite image. Table 13.2 shows the available layers provided by Google.
These overlays consist of a series of tiles that have the same size and dimension
as the base tiles. Most of the overlay tiles are made transparent so that you can see
the tile underneath. Whatever part of the tile is opaque becomes superimposed on
the underlying map (see Fig. 13.6 ). Overlaying transparent tiles in this way is faster
than overlaying individual points or lines. Most maps supplied by these services are