Geographic data is recorded
information about the earth's surface and the objects found on it,
associated to a geographic location. Listed below are key points you should
remember about geographic data.
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Two models for representing
real-world features in a GIS are the vector data model and the raster
data model.
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Geodatabases, shapefiles, and
coverages are common file formats for storing vector data. Images and
grids are common formats for raster data. |
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There are three types of
geodatabases: file geodatabases, personal geodatabases for Microsoft
Access, and ArcSDE geodatabases that are used with relational database
management systems and ArcSDE technology. |
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Geodatabase feature classes
can be stand-alone or they can be organized into larger units called
feature datasets. |
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The field type of an
attribute determines the type of data that can be stored in it.
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Before you build a
geodatabase, you need to spend time designing it. |
Review questions
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When would you use the vector
data model versus the raster data model?
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In a geodatabase polygon
feature class, which two fields are automatically calculated and
updated?
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List three methods of adding
data to a geodatabase.
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If you wanted to combine
features from different feature classes into one feature class, which
method would you use?
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If you want to
represent features with distinct boundaries, it's probably
better to use the vector data model and store the features' x,y
coordinate locations. The raster data model is better suited to
representing phenomena whose boundaries change gradually across
a given area.
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In a geodatabase
polygon feature class, the Shape_Length and Shape_Area fields
are automatically calculated and updated.
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Three methods of
adding data to a geodatabase are importing, loading, and copying
data.
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To combine features
from different feature classes into one feature class, you would
load them into a new, empty geodatabase feature class.
Key terms