[Liblas-commits] laszip: adding content to webpage

[liblas-commits at liblas.org]

details:   http://hg.liblas.orglaszip/rev/54cb2defd33c
changeset: 180:54cb2defd33c
user:      isenburg
date:      Fri Feb 04 19:19:52 2011 -0800
description:
adding content to webpage

diffstat:

 docs/source/index.rst |  42 ++++++++++++++++++++++++++++++------------
 1 files changed, 30 insertions(+), 12 deletions(-)

diffs (67 lines):

diff -r f9255b38465b -r 54cb2defd33c docs/source/index.rst
--- a/docs/source/index.rst	Tue Feb 01 11:18:40 2011 -0600
+++ b/docs/source/index.rst	Fri Feb 04 19:19:52 2011 -0800
@@ -18,6 +18,8 @@
 
   - See `OSGeo4W <http://trac.osgeo.org/osgeo4w>`__ for Windows release.
 
+  - Or try `laszip.exe`_ a very efficient standalone implementation based
+    on the lighter-weight `LASlib`_ API used by `LAStools`_
 
 Development Source
 ..............................................................................
@@ -33,25 +35,41 @@
 It has been provided as an `LGPL`_-licensed stand-alone software library to allow 
 other softwares that handle LAS data to read and write LASzip-compressed data.  
 libLAS can optionally take advantage of LASzip as of libLAS 1.6.0b4 to read 
-and write compressed data. Currently, both LAStools and libLAS can 
-interchange data using LASzip compression
+and write compressed data. Currently, both LAStools and libLAS can interchange
+data using LASzip compression.
 
-The compression can be many times smaller and many times
-faster than `bz2`_, `gzip`_, and `rar`_ due to the fact that it can take advantage 
-of known and regular data patterns that exist in LAS data.  LASzip uses 
-two widely known and open compression techniques that have been adapted to 
-LAS data to accomplish its task.  The first is a 
+The compression can be many times smaller and many times faster than `bz2`_,
+`gzip`_, and `rar`_ because it takes advantage of knowing what the different
+bytes in a LAS file represent. For example, the x and y coordinate of a
+point are predicted by adding their delta in the preceding two points to 
+the x and y of the last point, whereas the gps_time difference between
+subsequent points is expressed as a multiple of the most common increment,
+while RGB valued are compressed with simple difference coding. In each case
+the prediction residuals are compressed with adaptive arithemetic coding.
 
+The compressor treats the LAS points of types 0, 1, 2, 3, 4, 5, and 6  as 
+onsisting of a number of items: POINT10, GPSTIME11, RGB12, and WAVEPACKET13
+and uses separate modules with separate version numbers to compress each
+item. This makes it easy to improve, for example, the compressor for the
+gps_time without affecting the other compression schemes, while at the same
+time guaranteeing full backwards compatability. More importantly it allows
+to add new LAS point types as the LAS specification evolves into the future.
 
+Another advantage of LASzip over generic compressors is that it allows you
+to treat the compressed LAZ files just like standard LAS files and load them
+directly from compressed form into your application without the need to ever
+uncompress them points. The availability of reading and writing compressed
+LAZ files via the two APIs `libLAS`_ and `lasLIB`_ makes it easy to add 
+native LAZ support to your own software package.
 
 
-
-
-
-.. _`Martin Isenburg`: http://www.cs.unc.edu/~isenburg/lastools/
+.. _`Martin Isenburg`: http://www.cs.unc.edu/~isenburg
 .. _`ASPRS LAS format`: http://www.asprs.org/society/committees/standards/lidar_exchange_format.html
 .. _`LGPL`: http://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License
 .. _`bz2`: http://en.wikipedia.org/wiki/Bzip2
 .. _`gzip`: http://en.wikipedia.org/wiki/Gzip
 .. _`rar`: http://en.wikipedia.org/wiki/Rar
-.. _`LAStools`: http://lastools.org
\ No newline at end of file
+.. _`LAStools`: http://lastools.org
+.. _`libLAS`: http://liblas.org
+.. _`lasLIB`: http://www.cs.unc.edu/~isenburg/lastools/download/laslib.zip
+.. _`laszip.exe`: http://www.cs.unc.edu/~isenburg/lastools/download/laszip.exe