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Support loading polygon from SHP file
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<html>
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<title>Shapefile C Library</title>
<link href="maptools.css" rel="stylesheet" type="text/css">
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<body>
<h1>Shapefile C Library</h1>

<h2>Purpose</h2>

The Shapefile C Library provides the ability to write simple C programs
for reading, writing and updating (to a limited extent) ESRI Shapefiles,
and the associated attribute file (.dbf).<p>

<h2>Supporting Information</h2>

<ul>
<li> <a href="shp_api.html">Shapefile API Docs</a>
<li> <a href="dbf_api.html">DBF/xBase API Docs</a>
<li> <a href="shapelib-tools.html">Shapefile Tools Docs</a>
<li> <a href="release.html">Release Notes</a>
<li> <a href="manifest.html">Shapelib File Manifest</a>
<li> <a href="license.html">Shapelib Licensing Terms</a>
</ul>

<h2>What is a Shapefile?</h2>

If you don't know, you probably don't need this library.  The Shapefile
format is a working and interchange format promulagated by 
<a href="http://www.esri.com/">ESRI</a> for simple vector data with attributes.
<p>

An excellent <a href="dl/shapefile.pdf">white paper</a> on the shapefile format 
is available from ESRI,
but it is .pdf format, so you will need Adobe Acrobat to browse it.<p>

The file format actually consists of three files.<p>

<pre>
XXX.shp - holds the actual vertices.
XXX.shx - hold index data pointing to the structures in the .shp file.
XXX.dbf - holds the attributes in xBase (dBase) format.  
</pre>

<h2>Download</h2>

Source code, and some other odds and ends can be downloaded from
<a href="http://download.osgeo.org/shapelib">http://download.osgeo.org/shapelib</a>.<p>

Shapelib is available for anonymous CVS access:

<pre>
  cvs -d :pserver:cvsanon@cvs.maptools.org:/cvs/maptools/cvsroot login
  Password: (hit enter)
  cvs -d :pserver:cvsanon@cvs.maptools.org:/cvs/maptools/cvsroot co shapelib
</pre>

<h2>Bugs, Maintainance and Support</h2>

This library is maintained by <a href="http://pobox.com/~warmerdam">Frank 
Warmerdam</a>.  Please send me bug reports, patches and suggestions for the 
library via the <a href="http://bugzilla.maptools.org/enter_bug.cgi?product=Shapelib">maptools.org Bugzilla</a>.  Shapelib bugs can also be
<a href="http://bugzilla.maptools.org/query.cgi?product=Shapelib">queried</a>.
<p>

Shapelib is hosted at 
<a href="http://shapelib.maptools.org">shapelib.maptools.org</a>.   A mailing
list for discussion of how to use shapelib, and announcing new releases 
<a href="http://lists.maptools.org/mailman/listinfo/shapelib/">is 
available</a>.  To only find out about new releases of Shapelib select the 
"<i>Subscribe to new releases</i>" option from the link at 
<a href="http://freshmeat.net/projects/shapelib/">Freshmeat</a>.<p>

<h2>Credits</h2>

I didn't start this section anywhere near soon enough, so alot of earlier
contributors to Shapelib are lost in pre-history.

<ul>
<li> Bill Miller (NY-DOT) for shputils.c
<li> Carl Anderson for the contents of the contrib directory, and 
the "tuple" additions to dbfopen.c.
<li> Andrea Giacomelli for patches for dbfopen.c.
<li> Doug Matthews for portability improvements.
<li> Jan-Oliver Wagner for convincing me to make it available under LGPL,
shared library support, and various other patches.
<li> Dennis Christopher (of Avenza) for testing and bug fixes.
<li> Miko Syrjä (of 3D-system Oy) for a record size bug fix.
<li> Steven Lime and Curtis Hill for help with NULL shapes.
<li> Jim Matthews for support of NULL attributes in dbf files.
<li> <a href="http://www.pcigeomatics.com/">PCI Geomatics</a> who let me
release a modified version of their shapefile code in the beginning and
who hosted shapelib for years.
</ul>

<h2>In Memorium</h2>

I would like to dedicate Shapelib to the memory of Sol Katz.  While I never
met him in person, his generous contributions to the GIS community took 
many forms, including free distribution of a variety of GIS translators
with source.  The fact that he used this Shapelib in some of his utilities, 
and thanked me was a great encouragement to me.  I hope I can do his memory 
honour by trying to contribute in a similar fashion.<p>

<h2>Portability</h2>

The Shapefile C Library should port easily to 32bit systems with ANSI C
compilers.  It should work on 64 bit architectures (such as the DEC AXP).<p>

Care should also be taken to pass the binary access flag into SHPOpen()
and DBFOpen() when operating on systems with special text file translation
such as MSDOS.<p>

The shputils.c module is contributed, and may not take the same approach
to portability as the rest of the package.<p>

On Linux, and most unix systems it should be possible to build and 
install shapefile support as a shared library using the "lib" and "lib_install"
targets of the Makefile.  Note that this Makefile doesn't use autoconf
mechanisms and will generally require some hand tailoring for your environment.

<h2>Limitations</h2>

<ul>

<li> You can't modify the vertices of existing structures (though you 
   can update the attributes of existing structures, and create new 
   structures).<p>

<li> Not written in such a way as to be particularly fast.  This is 
particularly true of the 1.2 API.  For applications more concerned with
speed it may be worth using the V1.1 API.<p>

<li> Doesn't set the last access time properly in the .dbf files.<p>

<li> There is no way to synchronize information to the file except to close it.
<p>

<li> Poor error checking and reporting.<p>

<li> Not professionally supported (well it can be, if you want to pay).<p>

<li> Some aspects of xBase files not supported, though I believe they are
not used by ESRI.<p>

<li> The application must keep the .dbf file in sync with the .shp/.shx
files through appropriate use of the DBF and SHP APIs.<p>

<li> No support for the undocumented .sbn/.sbx spatial index files.<p>

</ul>

<h2>Other Shapefile Resources</h2>

<ul>
<li> <a href="dl/shapefile.pdf">Shapefile Format Specifications (pdf)</a><p>

<li> <a href="http://www.clicketyclick.dk/databases/xbase/format/">Xbase (.dbf) File Format Description</a>. <p>

<li> <a href="codepage.html">Language ID / Code Page mappings</a><p>

<li> Shapelib is used within the multiformat 
<a href="http://ogr.maptools.org/">OGR</a> library.  If you are looking for a 
high level C++ library with support for many geospatial vector formats you
might want to check it out.<p>

<li> Ari Jolma has produced an initial <b>perl</b> binding on top of shapelib, 
which can be found at CPAN as Geo::ShapeFile under the 
<a href="http://www.cpan.org/modules/by-module/Geo/">Geo</a> module.
<p>

<li> Bernhard Herzog has produced <b>python</b> bindings for Shapelib with 
SWIG, available at <a href="http://ftp.intevation.de/users/bh/pyshapelib/">http://ftp.intevation.de/users/bh/pyshapelib</a>.  A new version not using swig is 
available as <a href="http://wald.intevation.org/plugins/scmsvn/viewcvs.php/trunk/thuban/libraries/pyshapelib/?root=thuban">part of Thuban</a>.<p>

<li> <a href="http://www.triplexware.huckfinn.de/shpapi.html">Delphi</a>
bindings for Shapelib courtesy of Alexander Weidauer.<p>

<li> Miguel Filgueiras has implemented 
<a href="http://www.ncc.up.pt/gpsmanshp/">Tcl</a> bindings for Shapelib
as part of <a href="http://www.ncc.up.pt/gpsman/">GPSMan</a>.<p>

<li> David Gancarz has implemented a Microsoft
<a href="dl/contrib/DotNetArchive.zip">.NET wrapper</a> for
Shapelib.   An example of using shapelib with VB6 is also icluded in the .NET wrapper project file.<p>

<li> Andrey Hristov (php at hristov dot com) has developed a PHP extension 
based on Shapelib.  It can be found in CVS at http://cvs.php.net/pecl/shp.<p>

<li> Toyoda Eizi has developed Ruby bindings found at
<a href="http://sourceforge.net/projects/ruby-shapelib">http://sourceforge.net/projects/ruby-shapelib</a>.<p>

<li> Davide Cesari has developed FORTRAN bindings that can be found at
<a href"http://www.webalice.it/o.drofa/davide/shapelib-fortran/">
http://www.webalice.it/o.drofa/davide/shapelib-fortran</a>.

<li> Jan-Oliver Wagner has implemented a commandline program
(<b>gen2shp</b>) for producing shapefiles from Arc/Info Generate format ASCII
files.  He maintains a <a href="http://intevation.de/~jan/gen2shp">web page</a> for his work. <p>

<li> Tom Russo has implemented a shpcs2cs program, which reprojects shapefiles
using arguments similar to the PROJ.4 cs2cs program including datum conversion.
Use as an alternate to the contrib/shpproj which doesn't do datums.  It is 
available at the bottom of Tom's <a href="http://www.swcp.com/~russo/shape_web/">Xastir Shapefile Resources</a> page. <p>

<li> 
Andrew Williamson's 
<a href="http://www.geocities.com/SiliconValley/Haven/2295/useful.html">Useful
Scripts and Stuff</a> page for ArcView, which includes ShapeChecker.<p>

<li> The University of Bonn <a href="http://katla.giub.uni-bonn.de/sfjava/">
sf4java</a> project apparently includes Java classes for reading Shapefiles.<p>

<li> The <a href="http://gis.esri.com/arcscripts/details.cfm?CFGRIDKEY=628102085">ShapeIO2</a> Visual Basic libraries may be of interest to those wanting
VB access to Shapefiles.  Also available <a href="http://shapelib.maptools.org/dl/contrib/ShapeIO2.zip">locally</a>.<p>

<li> The <a href="http://arcscripts.esri.com/details.asp?dbid=11810">ShapeFile Read/Write OCX</a> is another option for Visual Basic programmers.<p>

<li> <a href="http://www.casa.ucl.ac.uk/sanjay/software_isovistanalyst.htm">Isovist Analyst</a> is a sort-of-free isovist generating extension for 
ArcView using shapelib.<p>

<li> <a href="http://www.obviously.com/gis/shpdiff/">shpdiff</a> utility 
by Bryce Nesbitt.<p>

<li> <a href="http://www.aequometer.de/">Aequometer</a>: a program for 
MS Excel to calculate the area of polygons and export as shapefiles.<p>

</ul>

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