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USGS CMG "Shapefile" Definition

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This provides USGS CMG "shapefile" definition Shape File

  • A Shapefile is a digital vector (non-topological) storage format for storing geometric location and associated attribute information. The Shapefile format is created by ArcView and can be used by ArcView, ARC/INFO, ArcGIS and other widely used GIS software.
  • ArcView, ARC/INFO and ArcGIS are commercial GIS software packages for making maps and analyzing geographic data.
  • A Shapefile stores map (geographic) features and attribute data as a collection of files having the same prefix and the following file extensions (as described in the ArcView on-line help):
    • .shp - the file that stores the feature geometry. Required.
    • .shx - the file that stores the index of the feature geometry. Required.
    • .dbf - the dBASE file that stores the attribute information of features. Required.
    • .sbn and .sbx - the files that store the spatial index of the features. Optional. These two files can be created in ArcView. See ArcView's on-line help for more information.
    • .fbn and .fbx - the files that store the spatial index of the features for shapefiles that are read-only. Optional. These two files can be created in ArcView. See ArcView's on-line help for more information.
    • .ain and .aih - the files that store the attribute index of the active fields in a table or a theme's attribute table. Optional. These two files can be created in ArcView. See ArcView's on-line help for more information.
    • .prj - the file that stores the coordinate system information. Optional. This file can be created with and is used by the ArcView Projection Utility. It is not used by ArcView GIS Version 3.x or older versions, or by ARC/INFO versions previous to version 8.0.
    • .xml - metadata for ArcInfo 8.0, for using shapefiles on the Internet. Optional.
  • Since a Shapefile is non-topological it does not maintain spatial relationship information such as connectivity, adjacency, and area definition. This makes the format simpler but less capable when performing complex spatial analysis.

NOTE: An individual Shapefile is actually a collection of files as described above that must be moved or distributed as a group otherwise the shapefile can be rendered unusable.

"I don't see much sense in that," said Rabbit.
"No," said Pooh humbly, "there isn't. But there was going to be when I began it.
It's just that something happened to it along the way."

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Page Last Modified: Mon Nov 4 03:37:33 PST 2013  (chd)