The Tile-Based Mapping Transition in Cartography - Maps for the Future Children Education and Internet - page 160

Table 13.2 Standard layers
provided by Google. All
layers are tiled

Traffic Current traffic conditions

Photos Locations of available photographs

Labels Street, city, and boundary names

Webcams Locations of cameras with live imagery

Videos Locations of YouTube videos

Wikipedia Wikipedia pages for locations on map

Bicycling Biking paths and trails

Buzz Postings to Google Buzz

45 45 degree angle bird's-eye view

Terrain Shaded relief map

Transit Public transportation network

+ =

Fig. 13.6 The tile overlay method. A map tile on the left is overlaid with a transparent PNG file
with an opaque line. Combining the two tiles produces the display on the right

transparent tile overlays and have a particular theme such as traffic, webcams, or
photos.
Most of the layers that are offered by online mapping services are updated only
occasionally. An example of a frequently updated layer is traffic (see top map in
Fig. 13.7 ). This layer shows the speed of traffic for major streets in the larger cities
of the world and is updated continuously throughout the day. The maps are also
tiled at multiple levels of detail for faster download. Only those tiles are replaced
that need updating. The bottom map in Fig. 13.7 shows a bicycle path map that
completely covers the underlying street map, at least in urban areas. It is updated
only irregularly.
An example application of the overlay is the campus map for the University of
Nebraska at Omaha (see Fig. 13.8 ). Here, a map of the campus was first constructed
with vectors in Adobe Illustrator. Subsequently, the map was converted to the raster
PNG format and tiled through an online tiling service. Three different levels of
detail of tiles were created and combined with the Google Map as a layer. Layers
were also created for parking and the shuttle transportation network.
Figure 13.9 shows how the parking and shuttle layers are integrated within
Google Maps to provide to provide an overall view of the campus. All Google
Map functions are active, such as searching for a specific location or travel routing.