Shapefile

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The file format Shapefile (often Shape Data or Shape ) is an originally developed for ArcView software from ESRI format developed for spatial data.

Development

The shapefile is used as a quasi-standard in desktop GIS environment, since it is a fairly simple and relating to data quality little challenging format. Nevertheless, it is the format that are in the most common map data available. The support of free and commercial programs, and libraries (eg GeoTools and Deegree ) is as good as the shapefiles in any format. Many open source programs convert data from shapefiles into SQL in order for spatial databases.

Construction

A shapefile is not a single file, it consists of at least three files:

  • . shp is used to store geometry data
  • . dbf attribute data in dBASE format
  • . shx serves as an index of the geometry used to link the attribute data (also called attribute data )

Optional files

  • . atx attribute index
  • . sbx and. sbn index for table joins ( joins)
  • . rty and. ain index for table links (links)
  • . shp.xml metadata for shapefile
  • . prj projection of the data
  • . cpg to specify the character set used in the dbf. .

In a shapefile only elements of one type may be included, eg

  • Points,
  • Lines,
  • Areas (polygons )
  • Or multi -point

In addition to the particular type shapefile can only contain so-called zero shapes. These have no geometry, but like any other type of a record in the associated DBF file. Further distinction can be made between 2D and 3D geometries, geometries.

Optionally, the created design a shapefile ( line width, point style, colors, etc. ) in a legend file ( to ArcView 3.3 *. Avl, from ArcGIS ArcView 8 *. Lyr ) are saved, because this information is not stored within a shapefile. The legend file can be added in the theme properties after loading a shapefile.

Format restrictions

  • The size of the Shp - and DBF files must not exceed 2 gigabytes ( or 2 ^ 31 bits ) does not exceed.

The attribute database format for the DBF file components based an earlier dBase standard. This is accompanied by the following restrictions:

  • While the current dBase format as well as GDAL / OGR (as open-source software library for reading and writing shapefiles ) differs empty fields as null values ​​by the digit 0, ESRI software takes this distinction before.
  • Limited support for Unicode field names
  • Maximum length of the field name: 10 characters
  • Maximum number of fields: 255
  • Valid field types are floating point ( 13 characters), integer / integer, date without time storage ( 8 characters ) and description ( 254 characters )
  • Floating point numbers may contain rounding errors since they are stored as text
AutoCAD Geoinformation
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