Geographic Information Systems (GIS)

In class:

Administrative:

• Questions from the GPS materials?

Instructional:

In this session we discuss GIS and then head into a lengthy demo of Google Earth capabilities.

Geographic Information Systems (GIS):

• As always, a great place to start our research is Wikipedia and here's the GIS page.Other names include geographical information science and geospatial information studies, we'll stick to geographic information systems
• In simple terms, GIS is data organized geographically on maps
• Aerial photos → Satellite photos → Computer Aided Design/Mapping
• Raster (bitmapped images) versus vector (mathematical points, lines and polygons) - advantages and disadvantages from Wikipedia include:
  • Raster datasets record a value for all points in the area covered which may require more storage space than representing data in a vector format that can store data only where needed.
  • Raster data is computationally less expensive to render than vector graphics
  • There are transparency and aliasing problems when overlaying multiple stacked pieces of raster images
  • Vector data allows for visually smooth and easy implementation of overlay operations, especially in terms of graphics and shape-driven information like maps, routes and custom fonts, which are more difficult with raster data.
  • Vector data can be displayed as vector graphics used on traditional maps, whereas raster data will appear as an image that may have a blocky appearance for object boundaries. (depending on the resolution of the raster file)
  • Vector data can be easier to register, scale, and re-project, which can simplify combining vector layers from different sources.
  • Vector data is more compatible with relational database environments, where they can be part of a relational table as a normal column and processed using a multitude of operators.
  • Vector file sizes are usually smaller than raster data, which can be tens, hundreds or more times larger than vector data (depending on resolution).
  • Vector data is simpler to update and maintain, whereas a raster image will have to be completely reproduced. (Example: a new road is added).
  • Vector data allows much more analysis capability, especially for "networks" such as roads, power, rail, telecommunications, etc. (Examples: Best route, largest port, airfields connected to two-lane highways). Raster data will not have all the characteristics of the features it displays.
• Spatial (geographic data) versus Non-spatial (non-geographic data)
• Layers of data
• Let's discuss the uses for mapping information systems

Google Earth:Wikipedia describe Google Earth as “a virtual globe, map and geographical information program that was originally called EarthViewer 3D, and was created by Keyhole, Inc, a Central Intelligence Agency (CIA) funded company acquired by Google in 2004 (see In-Q-Tel). It maps the Earth by the superimposition of images obtained from satellite imagery, aerial photography and GIS 3D globe.” Google Earth is available in several versions:

• Google Earth free for Mac and PC (PC version will run on Linux under WINE with tinkering)
• Google Earth free for mobile: for iOS and Android
• Google Earth for Business for Mac and PC
• Google Earth for Google Maps browser plugin for HTML5 browsers (Chrome recommended)

Google Earth Demo:

• Search features
  • Fly to
  • Find Business
  • Directions
    • From address
    • To address
    • Play Tour (controls)

• Printable view
• Navigation
  • On screen controls
  • Ground-level view (use cursor keys for a first-person shooter scheme)
  • Street-level view
  • “Moving-the-man”
• Places
• Preferences window
• Layers
  • Borders and Labels
  • Places
  • Photos
  • Roads
  • 3D Buildings
  • Ocean

FUN STUFF: Search for the Titanic (activate shipwrecks layer, 3D buildings layer and search for 41°43'35" N, 49°56'54" W)