A Quick Introduction to GIS

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A Quick Introduction to GIS
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What is GIS?

• Definition Analysis that combine relational
  databases with spatial interpretation and outputs
  often in form of maps. A more elaborate
  definition is that of computer programs for
  capturing, storing, checking, integrating,
  analyzing and displaying data about the earth
  that is spatially referenced.

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A GIS Map Contains Layers

• A GIS map is made up of layers, or collections of
  geographic objects that are alike.
• To make a map, you can add as many layers as you
  like.

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Layers Contain Features or Surfaces

• Each geographic object in a layer --- each city,
  river, lake, or country --- is called a feature.
• Not all layers contain features. A single
  continuous expanse that changes from one location
  to another is called a surface.

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Features Have Shape and Size

• Features can be represented as one of three
  geometric forms
• A polygon
• A line
• A point
• This kind of data is called vector data.

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Surfaces have Numeric Values Rather that Shapes

• Surfaces have measurable values for any
  particular location on the earth
• This is raster dataa matrix of identically sized
  cells where each cell contains a measurement for
  that location.

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Features Have Location

• GIS uses a coordinate system to associate
  features with location
• These coordinate systems make use of Geodetic
  datums

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Features can be Displayed at Different Sizes

• Zoom and out changes the scale of the map
• Scale is the relationship between the size of the
  features on the map and their size in the
  physical world.

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Features are Linked to Information

• Information about the features in a layer is
  stored in a table.
• The table has a row for each feature and the
  columns values are attributes of that feature

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Tables

• The links between features and their attributes
  makes it possible to query and display the
  results on the map.

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Thematic Maps

• You can use attributes to create thematic
  maps---maps in which colors (or other symbols)
  are used to indicate attribute values.

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Features have Spatial Relationships

• You can also ask questions about spatial
  relationship among features.
• GIS uses coordinate information to compare
  locations

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You can Create New Features

• GIS can look for areas of overlap between
  features of different layers and create new
  features to identify these areas.

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ArcMap and ArcCatalog
ArcCatalog is the data management Application.
ArcMap is the application for making maps and
analyzing data.