GIS Basic : General GIS Definition

Posted on May 5, 2007 By : Mizake Laziaf
What is GIS?
A Geographic Information System (GIS) connects a variety of information about a place, including spatial data, for display, management and analysis. Spatial data are pieces of information about where things are located on the earth. For example, coordinates of latitude and longitude are a type of spatial data that tell us where something in the world is located. A map is a familiar way to display spatial data, but GIS is more than just a single map or a set of spatial coordinates.

GIS uses a computer and a special software program to make digital maps. We can use GIS to discover the location of old buildings, roads, and other features by entering historic maps in the GIS program. These digitized maps are precisely REGISTERED (see example) to known points on the ground. Through registration, we can estimate the present location of past features on our maps.

Map features are displayed in GIS as LAYERS. Each layer consists of a single element of map data, such as buildings, roads, sewers, gardens, or archaeological excavations. These layers can be “stacked” so that a complete picture of all of the features – historic, archaeological, natural and modern – can be displayed at once. One of the most exciting features of GIS is that the layers from different maps can also be stacked to create a picture of change over time. This function of GIS helps us learn about the changing landscape of the Vancouver National Historic Reserve.

Information about the individual entities comprising a GIS layer is stored in a TABLE that is linked to the layer displayed on the map. In the GIS program, when you click on a building, all the table data about that building is displayed. This table can be used to obtain additional information about the features of a layer, such as a building shown on a historic map, or an archaeological excavation.

In addition to the display and management of map data, the power of GIS allows us to explore and discover new spatial relationships. The information stored in the system can be analyzed, recombined, and transformed to reveal new relationships and create new knowledge. This knowledge leads to a better understanding and appreciation of our cultural and natural resources, and contributes to the management, research, and interpretive goals of the Vancouver National Historic Reserve and the National Park Service.

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