EDUCACIÓN INICIAL Y PREESCOLAR

GIS color-graphic display capabilities are perhaps the most important reason for the popularity of modern spatial data management systems. It is the visual portrayal of spatial data and analysis results that helps communicate the character of our natural and built environment. Combined with user-friendly interfaces and interaction functions, GIS provides a flexible means for those of vary- ing skill levels to access and view spatial data and learn about management plans and engineering design proposals.

Map design is an important factor for the accurate and consistent portrayal of spatial information. Some basic cartographic principles apply whether the map is displayed on the color-graphic screen (soft copy) or printed on a color plotter. The basic cartographic elements of a map include a title, leg- end, scale, and north arrow. The legend translates the symbols into words. The scale expresses the ratio between ground coordinates and the map space, and is referred to as the representative fraction (RF) or natural scale. It is also useful to include a graphic or bar scale as well as a ratio, since the

Marshes Water Farm land Aquatic bed Wet meadow

FiGure 4.13 (see color insert following page 136.) Image-processing techniques are used to classify

land characteristics. Example shown identifies wetland areas in mixed agricultural landscape. (Hsu and Johnson 2007).

map display may be arbitrarily reduced or magnified by the user. The map should have a border or “neat line” defining the visual frame for the map, and a coordinate reference graticule or grid should also be shown. Text inserts for place names, credits, and other annotations are required to explain what the map is about, and these should be consistent in font type and size. An inset places the map coverage into its regional context.

A typical GIS provides basic symbology functions to represent features in an abstract manner. Various graphic standards have been adopted to represent features that are distinctive to certain applications. For example, symbols for the USGS topographic quadrangle maps are extant stan- dards (Figure 4.14). Similarly, industry-specific symbols for valves and pumps are standardized for the waterworks industry.

Color representation is also an important factor in map design and symbology, as colors have inherent appeal and meaning to the viewer. For example, color sequencing to show values should be even, flowing from dark to light, with dark being high and light low. Color changes are appropri- ate to distinguish between opposites on the same map (e.g., above/below a statistical mean). Color balance is essential, and all colors of the rainbow should rarely be used. Cartographic conventions should be adhered to, such as north at the top of the map. Also, contours are frequently brown; water features are cyan (blue); roads are red; and vegetation and forest areas are green. Areas colored red generally suggest some type of critical alert to the viewer, whereas green is generally considered to represent “safety.”

Masonry Dam

Large Falls; Small Rapids Small Falls; Small Rapids Perennial River Perennial Stream Disappearing Stream Intermittent River Intermittent Stream

Dam with Lock Dam Carrying Road

Dry Lake Narrow Wash Wide Wash

Well or Spring; Spring or Seep Aqueduct Tunnel

Elevated Aqueduct, Flume, or Conduit Canal, Flume, or Aqueduct with Lock Perennial Lake; Intermittent Lake or Pond RIVERS, LAKES, AND CANALS

FiGure 4.14 USGS symbology for hydrographic features. (Source: http://erg.usgs.gov/isb/pubs/booklets/

User interfaces provide the means for user access and interaction. Most GISs provide the stan- dard modern interfaces using command icons, windows, menu lists, and mouse selection functions. Interaction modes are provided for novice users who would make selections from menus and icons. Expert users may want to bypass the user interface to speed up and/or automate command selec- tions. For these users, a programming language environment is provided, perhaps as macro utilities that call and execute the commands, or as a higher level programming language, such as MS Visual Basic for Applications (VBA) or Python, through which command sequences can be enabled. Most GISs provide functionality for customizing the interface. For implementation in a large organization, the usability of the interface needs to be established through evaluation feedback and training.

Report generation is another key feature of a GIS. The GIS typically provides a capability to interactively select map features, retrieve tabular data associated with those features, and print those tables for reporting. Visualization is a relatively new dimension of computing engendered by faster computers and higher resolution display devices. Scientific visualization attempts to merge the processing power of the human brain with the display and processing power of the computer. The result is an enhanced capability for identification of patterns and relationships visible in the data but not detectable using ordinary descriptive and statistical methods. GIS software is advanc- ing to 3-D display and animation capabilities that support visualizations of complex environmental phenomena over time.

Model integration involves the use of the GIS in an integrated model-development environment. Intrinsic GIS analysis functions can be combined in modeling sequences so that a user can conduct modeling exercises in a user-friendly way by accessing compatible data sets and executing the model in a rapid and iterative manner. Exogenous models can be merged with the GIS modeling package as a seamless integrated modeling environment for specialized applications. This data and model integration capability of a GIS finds wide application in environmental and water resources engineering and is a primary focus of this book.

Internet and network access expand the horizons of GIS beyond just the single workstation. It has become routine, for example, to access and download digital map data over the Internet. Sharing files and GIS databases over a network is also commonplace. The network may be internal to an organization (intranet) or wider through connections to distant offices, colleagues, and clients. Also, an organization or individual can create a Web page and serve map products and data. The possibili- ties for GIS data and product sharing continue to expand through use of the Internet.

4.12 ManaGeMent MOdels