/*! \page sdts_al_main

<center>
<title>SDTS Abstraction Library</title>
</center>

<h2>Introduction</h2>

SDTS_AL, the SDTS Abstraction Library, is intended to be an relatively
easy to use library for reading vector from SDTS TVP (Topological Vector
Profile) files, primary DLG data from the USGS.  It also include support
for reading raster data such as USGS DEMs in SDTS format.   It consists
of open source, easy to compile and integrate C++ code.<p>

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<h2>SDTS Background</h2>

The USGS SDTS Page at 
<a href="http://mcmcweb.er.usgs.gov/sdts/">http://mcmcweb.er.usgs.gov/sdts</a>
is the definative source of information on the SDTS format.  The SDTS
format is based on the 
<a href="http://starship.skyport.net/crew/tibs/iso8211/faq.html">ISO 8211</a>
encoding scheme for the underlying files, and the SDTS Abstraction Library
uses 
<a href="http://gdal.velocet.ca/projects/iso8211/index.html">ISO8211Lib</a>
library to decode them.  All references to DDF* classes are from ISO8211Lib.<p>

An SDTS Transfer is a grouping of ISO8211 encoded files (ending in the
.DDF extension), normally with part of the basename in common.  For instance
a USGS DLG SDTS transfer might consists of many files matching the 
SC01????.DDF pattern.  The key file in an SDTS transfer is the catalog
file, such as SC01CATD.DDF.<p>

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<h2>Development Information</h2>

The <a href="class_sdtstransfer-include.html">sdts_al.h</a> 
include file contains the definitions for all public 
SDTS classes, enumerations and other services.<p>

The SDTSTransfer class is used to access a transfer as a whole.  The 
SDTSTransfer::Open() method is passed the name of the catalog file,
such as SC01CATD.DDF, to open.<p>

The SDTSTransfer analyses the catalog, and some other aspects of the
transfer, and builds a list of feature layers.  This list can be
accessed using the SDTSTransfer::GetLayerCount(), SDTSTransfer::GetLayerType(),
and SDTSTransfer::GetLayerIndexedReader() methods.  A typical TVP (Topological
Vector Profile) transfer might include three point layers (of type 
SLTPoint), a line layer (of type SLTLine), a polygon layer (of type SLTPoly)
as well as some additional attribute layers (of type SLTAttr).  the
SDTSTransfer::GetLayerIndexedReader() method can be used to instantiate a 
reader object for reading a particular layer. (NOTE: raster layers are
handled differently).<p>

Each type of SDTSIndexedReader (SDTSPointReader, SDTSLineReader, 
SDTSPolygonReader, and SDTSAttrReader) returns specific subclasses of
SDTSIndexedFeature from the SDTSIndexedReader::GetNextFeature() method.
These classes are SDTSRawPoint, SDTSRawLine, SDTSRawPolygon and 
SDTSAttrRecord.  These classes can be investigated for details on the
data available for each.<p>

See the <a href="sdts_al_tut.html">SDTS_AL Tutorial</a> for more information
on how to use this library.<p>

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<h2>Building the Source on Unix</h2>

<ol>

<li> First, fetch the source.  The most recent source should be accessable
at an url such as 
<a href="ftp://gdal.velocet.ca/pub/outgoing/sdts_1_3.tar.gz">
ftp://gdal.velocet.ca/pub/outgoing/sdts_1_3.tar.gz</a>.<p>


<li> Unpack the source.<p>
<pre>
% gzip -d sdts_1_3.tar.gz
% tar xzvf sdts_1_3.tar.gz
</pre>

<li> Type ``configure'' to establish configuration 
options. <p>

<li> Type make to build sdts_al.a, and the sample
mainline sdts2shp.<p>

</ol>

See the <a href="sdts_al_tut.html">SDTS_AL Tutorial</a> for more information
on how to use this library.<p>

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<h2>Building the Source on Windows</h2>

<ol>

<li> First, fetch the source.  The most recent source should be accessable
at an url such as 
<a href="ftp://gdal.velocet.ca/pub/outgoing/sdts_1_3.zip">
ftp://gdal.velocet.ca/pub/outgoing/sdts_1_3.zip</a>.<p>


<li> Unpack the source.<p>

<pre>
C:\SDTS> unzip sdts_1_3.zip
</pre>

<li> Build using makefile.vc with VC++.  You will need the VC++ runtime
environment variables (LIB/INCLUDE) set properly.  This will build the
library (sdts_al.lib), and the executables sdts2shp.exe, 8211view.exe and
8211dump.exe.<p>

<pre>
C:\SDTS> nmake /f makefile.vc
</pre>

</ol>

See the <a href="sdts_al_tut.html">SDTS_AL Tutorial</a> for more information
on how to use this library.<p>

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<h2>The sdts2shp Sample Program</h2>

The sdts2shp program distributed with this toolkit is primary intended to
serve as an example of how to use the SDTS access library.  However, it can
be useful to translate SDTS datasets into ESRI Shapefile format.  

<pre>
Usage: sdts2shp CATD_filename [-o shapefile_name]
                [-m module_name] [-v]

Modules include `LE01', `PC01', `NP01' and `ARDF'
</pre>

A typical session in which we inspect the contents of a transfer, and then
extract polygon and line layers might look like this:<p>

<pre>
warmerda[134]% sdts2shp data/SC01CATD.DDF -v
Layers:
  ASCF: `Attribute Primary         '
  AHDR: `Attribute Primary         '
  NP01: `Point-Node                '
  NA01: `Point-Node                '
  NO01: `Point-Node                '
  LE01: `Line                      '
  PC01: `Polygon                   '

warmerda[135]% sdts2shp data/SC01CATD.DDF -m PC01 -o pc01.shp
warmerda[136]% sdts2shp data/SC01CATD.DDF -m LE01 -o le01.shp
</pre>

A <a href="sdts2shp.zip">prebuilt executable</a> is available for
Windows.<p>

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<h2>Licensing</h2>

This library is offered as <a href="http://www.opensource.org">Open Source</a>.
In particular, it is offered under the X Consortium license which doesn't
attempt to impose any copyleft, or credit requirements on users of the code.<p>

The precise license text is:<p>

<em>
 Copyright (c) 1999, Frank Warmerdam
<p>
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
 to deal in the Software without restriction, including without limitation
 the rights to use, copy, modify, merge, publish, distribute, sublicense,
 and/or sell copies of the Software, and to permit persons to whom the
 Software is furnished to do so, subject to the following conditions:
<p>
 The above copyright notice and this permission notice shall be included
 in all copies or substantial portions of the Software.
<p>
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
<p>
</em>

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<h2>Author and Acknowledgements</h2>

The primary author of SDTS_AL is <a href="http://pobox.com/~warmerdam">
Frank Warmerdam</a>, and I can be reached at 
<a href="mailto:warmerdam@pobox.com">warmerdam@pobox.com</a>.  I am eager to 
receive bug reports, and also open to praise or suggestions.<p>

I would like to thank:<p>

<ul>
<li> <a href="http://www.safe.com/">Safe Software</a>
who funded development of this library, and agreed for it to be Open Source.<p>

<li> Mark Colletti, a primary author of 
<a href="http://mcmcweb.er.usgs.gov/sdts/sdtsxx/index.html">SDTS++</a> from
which I derived most of what I know about SDTS and ISO8211 and who was very 
supportive, answering a variety of questions.<p>

</ul>

I would also like to dedicate this library to the memory of Sol Katz.  
Sol released a variety of SDTS translators, at substantial
personal effort, to the GIS community along with the many other generous 
contributions he made to the community.  His example has been an inspiration
to me, and I hope similar efforts on my part will contribute to his memory.<p>

*/