1. Defining GIS
GIS (Geographic Information Systems) is a system of hardware and software used for storage, retrieval, mapping, and analysis of geographic data. Practitioners also regard the total GIS as including the operating personnel and the data that go into the system. Spatial features are stored in a coordinate system (latitude/longitude, state plane, UTM, etc.), which references a particular place on the earth. Descriptive attributes in tabular form are associated with spatial features. Spatial data and associated attributes in the same coordinate system can then be layered together for mapping and analysis. GIS can be used for scientific investigations, resource management, and development planning.
GIS differs from CAD and other graphical computer applications in that all spatial data is geographically referenced to a map projection in an earth coordinate system. For the most part, spatial data can be "re-projected" from one coordinate system into another, thus data from various sources can be brought together into a common database and integrated using GIS software. Boundaries of spatial features should "register" or align properly when re-projected into the same coordinate system. Another property of a GIS database is that it has "topology," which defines the spatial relationships between features. The fundamental components of spatial data in a GIS are points, lines (arcs), and polygons. When topological relationships exist, you can perform analyses, such as modeling the flow through connecting lines in a network, combining adjacent polygons that have similar characteristics, and overlaying geographic features.
GIS (Geographic Information Systems) is a technological field that incorporates geographical features with tabular data in order to map, analyze, and assess real-world problems. The key word to this technology is Geography – this means that the data (or at least some portion of the data) is spatial, in other words, data that is in some way referenced to locations on the earth. Coupled with this data is usually tabular data known as attribute data. Attribute data can be generally defined as additional information about each of the spatial features. An example of this would be schools. The actual location of the schools is the spatial data. Additional data such as the school name, level of education taught, student capacity would make up the attribute data. It is the partnership of these two data types that enables GIS to be such an effective problem solving tool through spatial analysis.
GIS operates on many levels. On the most basic level, GIS is used as computer cartography, i.e. mapping. The real power in GIS is through using spatial and statistical methods to analyze attribute and geographic information. The end result of the analysis can be derivative information, interpolated information or prioritized information.
A GIS (geographic information system) enables you to envision the geographic aspects of a body of data. Basically, it lets you query or analyze a database and receive the results in the form of some kind of map. Since many kinds of data have important geographic aspects, a GIS can have many uses: weather forecasting, sales analysis, population forecasting, and land use planning, to name a few.
In a GIS, geographic information is described explicitly in terms of geographic coordinates (latitude and longitude or some national grid coordinates) or implicitly in terms of a street address, postal code, or forest stand identifier. A geographic information system contains the ability to translate implicit geographic data (such as a street address) into an explicit map location. GIS developers sometimes obtain the map data from public sources or companies that specialize in collecting and organizing geographic information. The process of converting implicit geographic data into explicit or map-form images is called geocoding.
Geographic data can be stored in a vector graphics or a raster graphics format. Using a vector format, two-dimensional data is stored in terms of x and y coordinates. A road or a river can be described as a series of x,y coordinate points. Nonlinear features such as town boundaries can be stored as a closed loop of coordinates. The vector model is good for describing well-delineated features. A raster data format expresses data as a continously-changing set of grid cells. The raster model is better for portraying subtle changes such as soil type patterns over an area. Most geographic information systems make use of both kinds of data.
GISs do these kinds of things:
• They accept geographic input in the form of scanned-in and digitized map images. Often this data is supplied by a source that may own maps and has already digitized them.
• They rescale or otherwise manipulate geographic data for different purposes.
• They include a database manager, usually a relational database management system (RDBMS).
• They include query and analysis programs so that you can retrieve answers to simple questions such as the distance between two points on a map or more complicated questions that require analysis, such as determining the traffic pattern at a given intersection.
• They provide answers visually, usually as maps or graphs.
Similarities:
Looking at these three definitions some similarities can be noticed. A GIS (Geographic Information Systems) is system used to store, map, and analyze data. The data is spatial. This means that the data can be mapped using a coordinate system. Since GIS can be such a powerful tool it is seen in a wide variety of professions.
Differences:
Since GIS has several uses there are often differences in its definition. The first definition (http://www.nwgis.com/gisdefn.htm) mainly talks about the spatial aspects of GIS. Data within GIS have a particular coordinate system, and the data with the same coordinate system can be layered together and analyzed. Also, data can be "re-projected" from one coordinated system to another. When the data is "re-projected" to a new coordinate system the data should "register" or properly align. "Topology" is what defines the spatial relationships between features. The second definition (http://gislounge.com/what-is-gis/) refers more to the types of data stored in GIS. There are two types of data: spatial and attribute. The spatial data is where the data is located, and the attribute data is the additional information about the data. The example used in the definition is schools. The spatial data is where the schools are located, and the attribute data is any additional information that may be known about the school. The final definition (http://searchsqlserver.techtarget.com/definition/GIS) has to do with how the geographic data is stored. It can explicit, the geographic coordinates of the data, or implicit, such as a street address or a forest. When the implicit data is converted into explicit data it is called "geocoding". Data is also displayed in either vector or raster graphics. Raster models are best used for subtle changing features. While vector models are best used for well-delineated features.
2. Examples of GIS
Mortality Map of Heart Disease in White Males (1988-1992)
CDC/National Center for Health Statistics
Hyattsville, MD
This map was created using GIS to look at the heart disease of white males from 1988-1992. It was created by the CDC to analyze the distribution of heart disease cases nationwide.
The Geography of a Recession
This is a really interesting video that shows the progression of the recession by county. It starts in January 2007 and shows the change in unemployment rates month by month. It is really scary to see how much black (10.0% or over) there is by the end. It is like a plague that is taking over the nation.
Map of lava flows along Mauna Loa's northeast rift zone
Here is an example of GIS used to look at the lava flow along the Mauna Loa's northeast rift zone. This is a project by the Hawaiian Volcano Observatory.
3. Maps VS GIS
Although GIS is relatively new since it is a computer based program and maps have been hand drawn for several centuries, they are both a means of providing a user with valuable information. In addition, since they can be used to spatially display a wide variety of information they can be used in several fields. While GIS is a system that can create maps, it also stores, retrieves, and analyzes data. This data may or may not be found on the map. However, maps and GIS follow a similar idea: garbage in and garbage out. You may have accurate, interesting information, but if your display of it is poor you will lose your audience. GIS and maps are only as useful as the quality of the final product.
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