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GEOGRAPHIC INFORMATION SYSTEM. GIS are tools that allow for the processing of spatial data into information, generally information tied explicitly to, and used to make decision about, some portion of the earth. There is no absolutely agreed upon definition of a GIS.

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geographic information system
GEOGRAPHIC INFORMATION SYSTEM
  • GIS are tools that allow for the processing of spatial data into information, generally information tied explicitly to, and used to make decision about, some portion of the earth.
  • There is no absolutely agreed upon definition of a GIS
computer assisted cartographic cac systems
COMPUTER ASSISTED CARTOGRAPHIC (CAC) SYSTEMS
  • Computer systems designed to create maps from graphical objects combined with descriptive attributes, are excellent for display, but generally lack the analytical capabilities of GIS.
  • Input, design, and output of mappable data, rather than working through myriad analytics of the GIS to produce a simple map.
computer assisted drafting cad
COMPUTER ASSISTED DRAFTING (CAD)
  • A computer system developed to produce graphic images but not normally tied to external descriptive data files
  • It would not be as easy to use for producing maps as would CAC, nor would it be capable of analysing maps
definition of gis
DEFINITION OF GIS
  • A computer system for collecting, checking, integrating and analysing information related to the surface of the earth (Rhind 1988)
definition of gis1
DEFINITION OF GIS
  • A data input sub-system that collects and pre-processes spatial data from various sources. This sub-system is also largely responsible for the transformation of different types of spatial data.
  • A data storage and retrieval sub-system that organises the spatial data in a manner that allows retrieval, upgrading and editing.
definition of gis2
DEFINITION OF GIS
  • A data manipulation and analysis sub-system that performs task on the data, aggregates and desegregates estimates parameters and constrains and performs modelling functions.
  • A reporting sub-system that displays all or part of he database in tabular graphic or map form
comparison of cartographic process as applied to traditional cartography and gis
MAPS

Data Collection: aerial photos, surveys, etc.

Data processing: aggregation, classing, etc.; linear process

Map production: final step except for reproduction and dissemination

Map reproduction

GIS

Data collection:aerial photos, surveys,etc.

Data processing: aggregation, classing, plus analysis; circular process

Map production: not always final step;normally one map used to produce still more

Map reproduction

COMPARISON OF CARTOGRAPHIC PROCESS AS APPLIED TO TRADITIONAL CARTOGRAPHY AND GIS
analog versus digital gis a comparison of input subsystem functions
MAP

Input: recorded (compiled) on paper from a collected source

Points

Lines

Areas

GIS

Input:”encoded” into the computer from a collected source

Points

Lines

Areas

ANALOG VERSUS DIGITAL GISA COMPARISON OF INPUT SUBSYSTEM FUNCTIONS
analog versus digital gis a comparison of input subsystem functions1
MAP

Sources

Aerial photography

Digital remote sensing

Surveying

Visual descriptions

Census data

Statistical data, etc.

GIS

Sources

Same as map data

Digital line graph (DLG)

Digital elevation models (DEM)

Digital orthophotoquads

Other digital databases

ANALOG VERSUS DIGITAL GISA COMPARISON OF INPUT SUBSYSTEM FUNCTIONS
analog versus digital gis a comparison of storage and retrieval subsystem functions
MAP

Points, lines, and areas are drawn on paper with symbols

Retrieval is simply a matter of map reading

GIS

Points, lines and areas are stored as grid cells or coordinate pairs and pointers in computer

Attribute tables are associated with coordinate pairs

retrieval requires efficient computer search techniques

ANALOG VERSUS DIGITAL GISA COMPARISON OF STORAGE AND RETRIEVAL SUBSYSTEM FUNCTIONS
analog versus digital gis a comparison of analysis subsystem functions
MAP

Requires rulers, planimeters, compass, and other tools all used by the human analyst

Restricted to the data as they are aggregated and represented on the paper map

GIS

Uses the power of the computer to measure, compare, and describe contents of the database

Allows ready access to the raw data and allows aggregation and reclassification for further analysis

ANALOG VERSUS DIGITAL GISA COMPARISON OF ANALYSIS SUBSYSTEM FUNCTIONS
analog versus digital gis a comparison of reporting and output functions
MAP

Graphic device only

many forms of maps

Modifications can include cartograms, etc.

GIS

The map is only one type of GIS output

With minor exception, GIS offers same options as traditional hand-drawn maps

Also includes tables, charts, diagrams, photographs, etc.

ANALOG VERSUS DIGITAL GISA COMPARISON OF REPORTING AND OUTPUT FUNCTIONS