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Describe what a GIS is
Understand the two basic GIS data models
Describe the Geographic Approach to problem solving
Understand what you can do with GIS
Describe the two main types of coordinate systems
What is GIS?
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Geographic Information System (GIS) is a system that can be used to capture, store, manipulate, organize, distribute, visualize and analyze data in a geographic context. If a thing or phenomenon can be mapped via an address, XY coordinate, intersection, etc., it can be made part of a GIS. Once the thing or phenomenon is mapped in a GIS, it can be displayed, queried, analyzed and made ready for presentation. Examples:
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A successful GIS operates according to a well-designed plan and business rules, which are the models and operating practices (i.e., workflows) unique to each organization.
Turning geographic information into GIS data
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Data is generally gathered by observing and recording information through a variety of devices, methods, and behaviors. As you record information available in the real world, you process, organize, and synthesize it as a collection of digital files in a GIS database. Mapping this data may provide you with new information and possibly new data.
The Geographic Approach
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An individual cell represents a portion of the earth, such as a square meter or a square mile. The level of detail is determined by the size of each cell. For example, a 1x1m cell size would provide a very fine level of detail whereas a 100mx100x cell size would provide coarser data.
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Vector Data
The Vector data model is a coordinate-based data model that represents geographic features using sets of coordinate pairs (x,y) to represent locations on the earth. Using coordinate pairs we can define the three main types of vector geometry: points, lines, and polygons.
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A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth. A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. A GCS includes an angular unit of measure, a prime meridian, and a datum.
A A datum is a set of values used to define a specific geodetic system. A geodetic datum is a reference from which measurements are made. Datum is based on a reference ellipsoid, which is an approximation of the shape of the Earth. Ellipsoids are required because the earth is not a perfect sphere. A point is referenced by its longitude and latitude values. Longitude and latitude are angles measured from the earth's center to a point on the earth's surface. The angles often are measured in degrees (or in grads). The following illustration shows the world as a globe with longitude and latitude values.
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