GIS Overview

What is GIS? GIS is an information system that allows for capture, storage, retrieval, analysis and display of spatial data.

Characteristics of GIS? GIS Computer Software Data People Computer Hardware

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

Data Geographic data can include: –Remotely sensed data –GPS data –Census data –Road networks –Elevation data –Climate data –Power line coverage –Hydrography –Etc.

Data Spatially Referenced –geographic data contain information linking them to locations

Data Attributes –non-spatial characteristics of the features linked to their geographic locations

Data in GIS (vector model) Points (e.g., houses, cities) Lines (e.g., roads) Polygons (e.g., land parcels)

Data in GIS (raster model)

GIS Data Terminology Geographic information / data can be referred to in all of the following ways (and more) –geographic data –spatial data –geospatial data –map data –GIS data –GIS layer –coverage –shapefile –locational data From the Department of Redundancy Department

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

Computer Software Provides the ability to integrate, transform, analyze, and produce maps from geographic data to meet the needs of users

GIS In Practice: Project Design GIS projects are developed to address a problem or answer a research question Ideal Scenario: –Determine what output will best address the project goal(s) –Determine the analyses that can best produce that output –Determine what data are needed for those analyses Common Problems: –Analytical techniques may not be feasible due to inadequate software functionality, user training, time constraints, etc. –Data may be unavailable and too expensive to buy or collect –Data may be impossible to collect (e.g., historic data)

GIS In Practice: Data Acquisition Search GIS data available locally –Hard-drive, networked databases, CDs, DVDs, etc. Convert non-GIS data –Scan air-photos or digitize paper maps Search for free data online –Web searches of free data distribution sites Ask other people for data and/or for how to find it –Ask other members of a research group, field of study, etc. –This can be tricky since data are expensive in terms of money and time, can be sensitive/confidential, and may have great value to the person asked Buy the data –Typically find it via web searches of sites selling data Collect the data –Often expensive, slow, and difficult to do, and usually there are strings attached like needing research permits or IRB approval

GIS In Practice: Data Issues Storage –Decide where and how the data are going to be stored –Decide who will have access to these data –Decide how files will be named –Note: data storage is often given too little thought initially and not addressed until problems arise later in the project Metadata (data about the data) –Tells who created the data and how they did it –Ideally metadata will report the accuracy/quality of the data –New datasets should all have metadata files created for them

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

GIS In Practice: Preprocessing Common preprocessing steps include –Converting all datasets to the same projection –Clipping datasets to the same area –Changing the units (e.g., feet to meters) –Rescaling the data to the same resolution

GIS In Practice: Analysis Use existing functionality in a GIS Expanding the functionality of the GIS –Searching online for scripts that others have developed –Writing your own scripts Take advantage of functionality in other software –This can include other GIS packages –Using a remote sensing package to process satellite imagery and using output from that in a GIS –Using statistical software to perform an analysis that the GIS can not do Make your own software –This is what modelers do

GIS In Practice: Output Making maps or tables that fulfill the project needs –Making nice maps takes time and a good sense of design Incorporating the output into the larger project –Converting the maps to graphics for a report or slides for a presentation Interpreting the results –Important and challenging –Note: making maps is often easier than explaining what they mean

Quiz Time Turn the quiz in on your way out See you on Wednesday