Terms:
CAD Computer Aided Drafting (also Computer Aided Design)
used to be termed CAD/CAM (Computer Aids for Manufacturing) which
developed into numerical control for machine tools (robots)
Computer Aided Mapping (confusingly called CAM by some)
use of CAD software and hardware to manage the production and
reproduction of maps
AM/FM (Automated Mapping/ Facilities Management) another
acronym for computer aided mapping usually applied by facilities
managers such as utility companies.
Map Layer map coverage converted into digital system. Each
theme (attribute class) viewed as logically separate. (Critical
point: ability to integrate across layers)
Geographic Information Systems (GIS) a system of software
and hardware centered around the storage, manipulation, analysis
and display of spatially referenced information. Such systems
are embodied by people acting inside institutions (either public
or private). A GIS produces map output of potentially greater
flexibility than a computer aided mapping system.
More on definitions of GIS, Nick
Chrisman's Definition
Integration of data - spatial objects can be overlaid
to determine which ones coincide. The mathematical reference structure
to perform this ultimately derives from geodetic control. After
the physical overlay (registration of coordinates), the logical
overlay (often termed polygon overlay) must be computed so that
the attributes of one set of objects can be related to the attributes
of another. (Example: soil erosion as a physical process aggregated
and summarized by owner.)
Integration of disciplines - using different sources will
involve people trained in different disciplines, using different
approaches, definitions, etc. GIS offers a chance to extract more
value from each group's expertise, but this requires understanding.
Classic approach: project driven (Environmental Impact Statements),
database created for specific needs, when project ends, system
evaporates.
An alternative: routine functions of established institutions
maintain the database as a permanent part of their function. Existing
arrangements include much hidden duplication. Each component of
a database should be rationalized so that a single custodian is
selected. The custodian has an explicit societal (or corporate)
mandate to define the purpose and content of their contribution.
GIS offers gains in efficiency (reductions in cost or labor productivity),
but these require careful management. Many gains come from ability
to do things not done before: deeper analysis, more effectiveness,
greater equity in allocation.
GIS (in terms of just new system sales) is computed to be a
billion dollar industry in 1992; $10 billion in 1998. The training
system is inadequate for the level of demand. There is a potential
career in GIS for any student in this course.