rasterintro.html + r.compress manual: further compression description cleanup

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@69423 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.compress/r.compress.html

@@ -89,11 +89,12 @@ managed with <b>r.null -z</b>.
 <h3>COMPRESSION ALGORITHM DETAILS</h3>
 <!-- keep in sync with raster/rasterintro.html -->
 
-All types of raster maps are by default ZLIB compressed, i.e. the default
-ZLIB's deflate algorithm. The compression method can be set to RLE, ZLIB,
-LZ4, or BZIP2 with the environment variable <tt>GRASS_COMPRESSOR</tt>.
+All GRASS GIS raster map types are by default ZLIB compressed, i.e. using
+ZLIB's deflate algorithm. Through the environment variable
+<tt>GRASS_COMPRESSOR</tt> the compression method can be set to RLE, ZLIB,
+LZ4, or BZIP2.
 <p>
-Optionally integer (CELL type) raster maps can be compressed with RLE if
+Integer (CELL type) raster maps can be compressed with RLE if
 the environment variable <tt>GRASS_INT_ZLIB</tt> exists and is set to value 
 0. However, this is not recommended.
 <p>
@@ -107,7 +108,8 @@ they are either compressed with ZLIB, LZ4, BZIP2 or are uncompressed.
 <dt><strong>RLE</strong></dt>
 <dd><b>DEPRECATED</b> Run-Length Encoding, poor compression ratio but 
 fast. It is kept for backwards compatibility to read raster maps 
-created with GRASS 6. It is only used for raster maps of type CELL. 
+created with GRASS 6. It is only used for raster maps of type CELL.
+FCELL and DCELL maps are never and have never been compressed with RLE.
 </dd>
 <dt><strong>ZLIB</strong></dt>
 <dd>ZLIB's deflate is the default compression method for all raster 
@@ -115,7 +117,7 @@ maps. GRASS GIS 7 uses by default 1 as ZLIB compression level which is the
 best compromise betweeen speed and compression ratio, also when 
 compared to other available compression methods. Valid levels are in 
 the range [1, 9] and can be set with the environment variable 
-GRASS_ZLIB_LEVEL.</dd>
+<tt>GRASS_ZLIB_LEVEL</tt>.</dd>
 <dt><strong>LZ4</strong></dt>
 <dd>LZ4 is a very fast compression method, about as fast as no 
 compression. Decompression is also very fast. The compression ratio is 

raster/rasterintro.html

@@ -279,47 +279,47 @@ The GRASS GIS raster format is architecture independent and portable between
 <h3>Raster compression</h3>
 <!-- keep in sync with raster/r.compress/r.compress.html -->
 
-GRASS raster maps are by default ZLIB compressed. If the environment 
-variable <tt>GRASS_INT_ZLIB</tt> exists and has the value 0, newly 
-generated compressed integer (CELL type) raster maps will be compressed 
-using RLE compression instead of ZLIB.
+
+All GRASS GIS raster map types are by default ZLIB compressed, i.e. using
+ZLIB's deflate algorithm. Through the environment variable
+<tt>GRASS_COMPRESSOR</tt> the compression method can be set to RLE, ZLIB,
+LZ4, or BZIP2.
+<p>
+Integer (CELL type) raster maps can be compressed with RLE if
+the environment variable <tt>GRASS_INT_ZLIB</tt> exists and is set to value 
+0. However, this is not recommended.
 <p>
 Floating point (FCELL, DCELL) raster maps never use RLE compression;
 they are either compressed with ZLIB, LZ4, BZIP2 or are uncompressed.
-<p>
-The compression method for raster maps is by default ZLIB's deflate 
-algorithm. The compression method can be set with the environment 
-variable GRASS_COMPRESSOR which can be set to RLE, ZLIB, LZ4, or BZIP2.
 
 <dl>
 <dt><strong>RLE</strong></dt>
 <dd><b>DEPRECATED</b> Run-Length Encoding, poor compression ratio but 
-fast. Kept for backwards compatibility to read raster maps created with 
-GRASS 6. Only used for raster maps of type CELL. FCELL and DCELL maps 
-are never and have never been compressed with RLE.</dd>
+fast. It is kept for backwards compatibility to read raster maps 
+created with GRASS 6. It is only used for raster maps of type CELL.
+FCELL and DCELL maps are never and have never been compressed with RLE.
+</dd>
 <dt><strong>ZLIB</strong></dt>
 <dd>ZLIB's deflate is the default compression method for all raster 
-maps. GRASS 7 uses by default 1 as ZLIB compression level which is the 
+maps. GRASS GIS 7 uses by default 1 as ZLIB compression level which is the 
 best compromise betweeen speed and compression ratio, also when 
 compared to other available compression methods. Valid levels are in 
 the range [1, 9] and can be set with the environment variable 
-GRASS_ZLIB_LEVEL.</dd>
+<tt>GRASS_ZLIB_LEVEL</tt>.</dd>
 <dt><strong>LZ4</strong></dt>
 <dd>LZ4 is a very fast compression method, about as fast as no 
-compression. The compression ration is generally higher than for RLE. 
-Decompression is also very fast. LZ4 is recommended if disk space is 
-not a limiting factor, but some sving on disk space is welcomed without 
-increasing processing speed. The compression ratio of LZ4 is generally 
-better than for RLE but worse than for ZLIB.</dd>
+compression. Decompression is also very fast. The compression ratio is 
+generally higher than for RLE but worse than for ZLIB. LZ4 is 
+recommended if disk space is not a limiting factor.</dd>
 <dt><strong>BZIP2</strong></dt>
-<dd>BZIP2 can provide compression ratios much higher than for the other 
+<dd>BZIP2 can provide compression ratios much higher than the other 
 methods, but only for large raster maps (&gt; 10000 columns). For large 
 raster maps, disk space consumption can be reduced by 30 - 50% when 
 using BZIP2 instead of ZLIB's deflate. BZIP2 is the slowest compression 
 and decompression method. However, if reading from / writing to a 
 storage device is the limiting factor, BZIP2 compression can speed up 
 raster map processing. Be aware that for smaller raster maps, BZIP2 
-compression ratio can be worse than for other compression methods.</dd> 
+compression ratio can be worse than other compression methods.</dd> 
 </dl>
 
 <p>