Review

What is GIS? GIS is an information system that allows for capture, storage, retrieval, analysis and display of spatial data. All of those definitions have some things in common: -- computer, mapping, analysis, etc. So in spite of this confusion about what it is, there are some key characteristics of a GIS we can identify.

Characteristics of GIS? Computer Hardware Computer Software People Data The 1st group of characteristics computer software.

Computer Hardware Computers Disk storage Digitizers and scanners Printer and plotter output devices

Computer Software Location ability to recognize and integrate locational information from a variety of sources (spatial) - ability to recognize and integrate locational information from a variety of sources

Computer Software Attributes ability to associate attribute information with geographic locations

Computer Software Manipulation/Analysis Ability to manipulate or analyze the data to meet the needs of users. Overlays Buffers Distance calculations Within/adjacency operations

Data The geographic and attribute information itself Remotely sensed data GPS data Census data Road network Elevation data Climate data Power line coverage Hydrography Key characteristics. Data is a key characteristic to

Semantic Chaos Geographic Information / Data map data spatial data locational data

People People People users knowledgeable about geographic concepts and theory, GIS software, and data who can carry out the process

How Does GIS Work? Information System Chain of Operations Collecting Data Storing and Analyzing Data Using Information for Decision Making

How Does GIS Work? The first step of using a GIS is the collection of data Most data collection requires some type of data transformation Collecting Data

Four Major Mapping Transformations 1. Entity to Object real world entities to data Take a real world object and put it into a database. Location of a building Location of people Characteristics of an object

Four Major Mapping Transformations 2. Symbolization Transformation map to data - digitizing data to map – mapping entities with locational information

Four Major Mapping Transformations 3. Object to Object changes in data structure or scale Change scale

Four Major Mapping Transformations 4. Map Base Transformations mapping units (e.g. degrees, meters, feet) projection coordinate system datum Projection change

Algorithmic transformations in a GIS Used for these transformations: object to object base map transformations Geographic Data Transformation Algorithm=New Data New Data Geographic Data Algorithm An algorithm is simply a rule or set of procedures for solving a problem. GIS programmers code most of the algorithms we commonly use into GIS software. While many users of GIS are not algorithm programmers, the more you understand the fundamental concepts being carried out by algorithms, the better qualified you are as a user of the software. If the program doesn’t do what you need, develop your own transformation algorithms and write computer programs to execute them (C, Avenue, AML Visual Basic, etc.

How Does GIS Work? The next step is to store the data in a database Database organization is the key to a successful project Storing and Analyzing Data

Simple Database Example Orange Co. Processed Unprocessed Base Data Derived Data Satellite Images Land Cover Roads Cities Rates of Deforestation

How Does GIS Work? Once the database is complete, analysis can begin Analysis also involves the use of some algorithms Can be as simple as an overlay Can be as complex as a hydrological model Storing and Analyzing Data

How Does GIS Work? After analysis, the information is communicated, most often through a map The information can then be used to make decisions Using Information for Decision Making

Chloropleth This potential exists for nearly all maps. Source: http://www.gis.psu.edu/geog121/pop.html

Dot Density This potential exists for nearly all maps.

Cartogram 1995 2030 Change The Americas 775 1080 +39% This potential exists for nearly all maps. 1995 2030 Change The Americas 775 1080 +39% Europe 727 718 -1% Africa 728 1496 +105% Asia 3458 4960 +43% Source: http://www.gis.psu.edu/geog121/pop.html

Next Class Basic Geodesy READINGS Heywood, Chapter 1 (by Sept 7) Heywood, Chapter 2, pp. 20 – 34 (by Sept 12)