An Introduction To Geographic Information Systems

Geographic Information Systems (GIS) have been gaining popularity over recent years. This has spawned new jobs and the sub-discipline of Geographic Information Science, usually located within the Geography department of most colleges and universities. The forerunner in creating and distributing GIS software is the Environmental Systems Research Institute (ESRI) based in Redlands, California. ESRI is most recognized with their ArcGIS programs such as ArcMap, ArcCatalog, ArcScene, and ArcGlobe along with numerous tools and extensions for these programs. Within these programs, the user has the option to choose from different licensing options that open up more tools and extensions as you deviate from ArcEditor to ArcView and then to ArcInfo.

What can you do with GIS?

Geographic Information Systems input, store, edit, retrieve, output, and analyze spatial data. By spatial data, I mean any phenomena that occurs on the face of the earth. Everything is represented in GIS as either a point, line, or polygon. Roads are most often represented as lines, houses as points, and lakes as polygons (of course this all depends on the scale in which your working with).

Input: Before you can begin creating a map you must input relevant, accurate data. Perhaps you are creating a map of crimes within a particular city. You will need to have point data or a table of crimes and where they occurred, a roads layer, possibly a satellite orthophoto, and any other information that can be linked together. Depending on the purpose of the map, you may want to seek prevention of such crimes, awareness of them, or eliminate these crimes altogether by focusing on the source. Maybe police officers can patrol crime hot-spots or the city can increase lighting in areas where crimes are prevalent and lights are dim or non-existent. Some GIS data does cost money, but if you do a little digging it isn't very hard to find free downloadable GIS data. The USGS, DNR, and US Census have thousands of shapefiles, metadata, orthophotos, and more for no cost.

Store: Even if particular data is not being used, GIS allows easy storing and organization of data. ArcCatalog is a specific program that specializes in storing, organizing, deleting, and creating data. Storing data isn't as clear cut as you think as each shapefile must have metatdata, projection, and attributes just to name a few stored alongside. Metadata is "data about data" which is very important if you intend to share data or are using data created by another individual. Metadata will specify lots of information about when the data was created, for what purpose, under what scale and unit of measurement, what every abbreviation in the attribute table stands for. Essentially if you have any questions about the data you are using, the metadata should be able to answer them.

Edit: Our world is constantly changing, so editing data is required from time to time. New roads are built, families move, country boundaries change or are disputed for years or centuries. Whatever it may be, editing data is very important in producing accurate results.

Retrieve: Retrieving data can be done through your own database, an online server, a data deli, or others. Sometimes data has to be created if it doesn't already exist. This can be done by going out into the field and taking observations, collecting gps waypoints, digitizing data from satelitte images, and more.

Output: Work done through ArcMap can be viewed in Data View or Layout View. Data View is used when you are using tools and extensions, and doing other calculations. Layout View is for aligning the map and its ancillary components (north arrow, scale, title, neatline) so that it can be printed or exported as a .pdf or other image/document file. The map output is limited to the printer that you have. Maps can be created on 8.5" x 11" paper or on a plotter for a giant poster sized map.

Analyze: GIS is such a useful tool because of its analytical ability. Analyzing the data of your choice can help businesses run much more efficiently. By using GIS we can conduct target market advertising, build new stores in locations that need/want them, provide seamless rescue operations, find excellent locations for windmills and solar panels based on climatological data, and more. Currently corporate businesses, environmental agencies, local and federal government agencies, and engineering firms are choosing GIS to make their companies more efficient in more ways than one.