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- /*! \page vlibOgr OGR interface
- by GRASS Development Team (http://grass.osgeo.org)
- \par Table of contents
- - \ref vlibOgrIface
- - \ref vlibFrmtFileFormat
- - \ref vlibFidxFileFormat
- \section vlibOgrIface OGR interface
- \subsection vLibPseudoTopo Pseudo-topology
- Reduced topology: each boundary is attached to one area only,
- i.e. smoothing, simplification, removing small areas etc. will not
- work properly for adjacent areas or areas within areas.
- Full topology is only available for native GRASS vectors or can only
- be built after all polygons are converted to areas and cleaned as done
- by <tt>v.in.ogr</tt>.
- \subsection vlibFrmtFileFormat Frmt file format specification
- Frmt is a plain text file which contains basic information about
- external format of linked vector map. Each line contains key, value
- pairs separated by comma.
- OGR specific format is described by:
- - FORMAT - ogr
- - DSN - OGR datasource name
- - LAYER - OGR layer name
- Example:
- \verbatim
- FORMAT: ogr
- DSN: /path/to/shapefiles
- LAYER: cities
- \endverbatim
- OGR layer can be linked via <tt>v.external</tt> command. When linking
- OGR layer pseudo-topology ('topo') is built including spatial index
- file ('sidx') and category index file ('cidx'). Additionally also
- feature index file (see \ref vlibFidxFileFormat) is created.
- \subsection vlibFidxFileFormat Fidx file format specification
- Note: <tt>finfo</tt> is an instance of \ref Format_info structure.
- <table border="1" style="border-collapse: collapse" cellpadding="5">
- <tr><td><b>Name</b></td><td><b>Type</b></td><td><b>Number</b></td><td><b>Description</b></td></tr>
- <tr><td>Version_Major </td><td>C</td><td>1</td><td>file version (major)</td></tr>
- <tr><td>Version_Minor </td><td>C</td><td>1</td><td>file version (minor)</td></tr>
- <tr><td>Back_Major</td><td>C</td><td>1</td><td>supported from GRASS version (major)</td></tr>
- <tr><td>Back_Minor</td><td>C</td><td>1</td><td>supported from GRASS version (minor)</td></tr>
- <tr><td>byte_order</td><td>C</td><td>1</td><td>little or big endian
- flag; files are written in machine native order but
- files in both little and big endian order may be
- readl; zero for little endian</td></tr>
- <tr><td>length</td><td>L</td><td>1</td><td>header size</td></tr>
- <tr><td>fInfo.ogr.offset_num</td><td>I</td><td>1</td><td>number of records</td></tr>
- <tr><td>fInfo.ogr.offset</td><td>I</td><td>offset_num</td><td>offsets</td></tr>
- </table>
- */
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