r.import manual: explain missing resampling methods (#1557)

- r.import manual: explain missing resampling methods: explain bilinear_f, bicubic_f, lanczos_f
- r.proj + r.import manuals: sync of descriptions
- r.proj + r.import manuals:: sync of descriptions of the interpolation methods
- g/m/v.proj manuals: cross-refs added, minor cleanup

general/g.proj/g.proj.html

@@ -2,7 +2,13 @@
 
 <p><em>g.proj</em> provides a means of converting a co-ordinate system
 description (i.e. projection information) between various formats.
-If compiled without <a href="https://www.gdal.org/">OGR</a> present, the
+
+<p>
+For an introduction to map projections (with PROJ),see the manual page of
+<a href="r.proj.html">r.proj</a>.
+
+<p>
+If compiled without <a href="https://gdal.org/">OGR</a> present, the
 functionality is limited to:
 <ul>
 <li>Reporting the projection information for the current location, 
@@ -217,8 +223,8 @@ ogr2ogr -t_srs "`g.proj -wf`" polbnda_italy_GB_ovest.shp polbnda_italy_LL.shp
 <h2>REFERENCES</h2>
 
 <a href="https://proj.org">PROJ</a>: Projection/datum support library<br>
-<a href="https://www.gdal.org">GDAL raster library and toolset</a><br>
-<a href="https://www.gdal.org/">OGR vector library and toolset</a>
+<a href="https://gdal.org">GDAL raster library and toolset</a><br>
+<a href="https://gdal.org/">OGR vector library and toolset</a>
 
 <p><b>Further reading</b>
 <ul>

raster/r.proj/r.proj.html

@@ -3,7 +3,7 @@
 <em>r.proj</em> projects a raster map in a specified mapset of a
 specified location from the projection of the input location to a raster map
 in the current location. The projection information is taken from the
-current PROJ_INFO files, as set and viewed with 
+current PROJ_INFO files, as set and viewed with
 <em><a href="g.proj.html">g.proj</a></em>.
 
 <h3>Introduction</h3>
@@ -17,7 +17,8 @@ projections, with common ones divided into a number of classes,
 including cylindrical and pseudo-cylindrical, conic and pseudo-conic,
 and azimuthal methods, each of which may be conformal, equal-area, or
 neither.
-<p>The particular projection chosen depends on the purpose of the
+<p>
+The particular projection chosen depends on the purpose of the
 project, and the size, shape and location of the area of interest.
 For example, normal cylindrical projections are good for maps which
 are of greater extent east-west than north-south and in equatorial
@@ -29,7 +30,8 @@ used.  Conformal projections preserve angular relationships, and
 better preserve arc-length, while equal-area projections are more
 appropriate for statistical studies and work in which the amount of
 material is important.
-<p>Projections are defined by precise mathematical relations, so the
+<p>
+Projections are defined by precise mathematical relations, so the
 method of projecting coordinates from a geographic reference frame
 (latitude-longitude) into a projected cartesian reference frame (eg
 metres) is governed by these equations.  Inverse projections can also
@@ -38,14 +40,16 @@ be achieved.  The public-domain Unix software package <i>PROJ</i>
 manual contains a detailed description of over 100 useful projections.
 This also includes a programmers library of the projection methods to
 support other software development.
-<p>Thus, converting a vector map - in which objects are located with
+<p>
+Thus, converting a vector map - in which objects are located with
 arbitrary spatial precision - from one projection into another is
 usually accomplished by a simple two-step process: first the location
 of all the points in the map are converted from the source through an
 inverse projection into latitude-longitude, and then through a forward
 projection into the target.  (Of course the procedure will be one-step
 if either the source or target is in geographic coordinates.)
-<p>Converting a raster map, or image, between different projections,
+<p>
+Converting a raster map, or image, between different projections,
 however, involves additional considerations.  A raster may be
 considered to represent a sampling of a process at a regular, ordered
 set of locations.  The set of locations that lie at the intersections
@@ -62,12 +66,11 @@ step, since the source or client will frequently be in a different
 projection to the working projection.
 <p>In some cases it is convenient to do the conversion outside the
 package, prior to import or after export, using software such
-as <i>PROJ</i>'s
-<em><a href="https://proj.org/">cs2cs</a></em> [1]. This is an easy
-method for converting an ASCII file containing a list of coordinate points,
-since there is no topology to be preserved and <i>cs2cs</i> can be used to
-process simple lists using a one-line command. The <em>m.proj</em> module
-provides a handy front end to <tt>cs2cs</tt>. 
+as <i>PROJ</i>'s <em><a href="https://proj.org/apps/cs2cs.html">cs2cs</a></em>
+[1]. This is an easy method for converting an ASCII file containing a list
+of coordinate points, since there is no topology to be preserved and
+<i>cs2cs</i> can be used to process simple lists using a one-line command.
+The <em>m.proj</em> module provides a handy front end to <tt>cs2cs</tt>. 
 
 <p>Vector maps is generally more complex, as parts of the data stored in
 the files will describe topology, and not just coordinates. In GRASS
@@ -84,12 +87,14 @@ As discussed briefly above, the fundamental step in re-projecting a
 raster is resampling the source grid at locations corresponding to the
 intersections of a grid in the target projection. The basic procedure
 for accomplishing this, therefore, is as follows:
-<p><em>r.proj</em> converts a map to a new geographic projection. It
+<p>
+<em>r.proj</em> converts a map to a new geographic projection. It
 reads a map from a different location, projects it and write it out to
 the current location. The projected data is resampled with one of four
-different methods: nearest neighbor, bilinear, bicubic iterpolation or
+different methods: nearest neighbor, bilinear, bicubic interpolation or
 lanczos.
-<p>The <b>method=nearest</b> method, which performs a nearest neighbor
+<p>
+The <b>method=nearest</b> method, which performs a nearest neighbor
 assignment, is the fastest of the three resampling methods. It is
 primarily used for categorical data such as a land use classification,
 since it will not change the values of the data
@@ -103,24 +108,28 @@ average of the 25 surrounding cells in the input map. Compared to
 bicubic, lanczos puts a higher weight on cells close to the center and a
 lower weight on cells away from the center, resulting in slightly
 better contrast.
-<p>The bilinear, bicubic and lanczos interpolation methods are most
+<p>
+The bilinear, bicubic and lanczos interpolation methods are most
 appropriate for continuous data and cause some smoothing. The amount
 of smoothing decreases from bilinear to bicubic to lanczos. These
 options should not be used with categorical data, since the cell
 values will be altered.
-<p>In the bilinear, bicubic and lanczos methods, if any of the surrounding
-cells used to interpolate the new cell value are null, the resulting
-cell will be null, even if the nearest cell is not null. This will
-cause some thinning along null borders, such as the coasts of land
-areas in a DEM. The bilinear_f, bicubic_f and lanczos_f interpolation
-methods can be used if thinning along null edges is not desired.
+<p>
+In the bilinear, bicubic and lanczos methods, if any of the surrounding
+cells used to interpolate the new cell value are NULL, the resulting
+cell will be NULL, even if the nearest cell is not NULL. This will
+cause some thinning along NULL borders, such as the coasts of land
+areas in a DEM. The <b>bilinear_f</b>, <b>bicubic_f</b> and <b>lanczos_f</b>
+interpolation methods can be used if thinning along NULL edges is not desired.
 These methods &quot;fall back&quot; to simpler interpolation methods
-along null borders.  That is, from lanczos to bicubic to bilinear to
+along NULL borders.  That is, from lanczos to bicubic to bilinear to
 nearest.
-<p>If nearest neighbor assignment is used, the output map has the same
+<p>
+If nearest neighbor assignment is used, the output map has the same
 raster format as the input map. If any of the interpolations is used,
 the output map is written as floating point.
-<p>Note that, following normal GRASS conventions, the coverage and
+<p>
+Note that, following normal GRASS conventions, the coverage and
 resolution of the resulting grid is set by the current region
 settings, which may be adjusted
 using <em><a href="g.region.html">g.region</a></em>. The target raster
@@ -155,7 +164,8 @@ To avoid excessive time consumption when reprojecting a map the region
 and resolution of the target location should be set appropriately
 beforehand.
 
-<p>A simple way to do this is to check the projected bounds of the input
+<p>
+A simple way to do this is to check the projected bounds of the input
 map in the current location's projection using the <b>-p</b>
 flag. The <b>-g</b> flag reports the same thing, but in a form which
 can be directly cut and pasted into
@@ -166,7 +176,8 @@ with <em><a href="g.region.html">g.region</a></em>'s <b>-a</b>
 flag. E.g.
 <tt>g.region -a res=5 -p</tt>. Note that this is just a rough guide.
 
-<p>A more involved, but more accurate, way to do this is to generate a
+<p>
+A more involved, but more accurate, way to do this is to generate a
 vector "box" map of the region in the source location using
  <em><a href="v.in.region.html">v.in.region -d</a></em>.
 This "box" map is then reprojected into the target location with
@@ -178,7 +189,8 @@ Latitude/Longitude locations to measure the geodetic length of a
 pixel).
 <em>r.proj</em> is then run for the raster map the user wants to
 reproject.  In this case a little preparation goes a long way.
-<p>When reprojecting whole-world maps the user should disable
+<p>
+When reprojecting whole-world maps the user should disable
 map-trimming with the <b>-n</b> flag. Trimming is not useful here
 because the module has the whole map in memory anyway. Besides that,
 world "edges" are hard (or impossible) to find in projections other
@@ -245,6 +257,7 @@ r.proj input=elevation location=ll_wgs84 mapset=user1 memory=800
 </pre></div>
 
 <h3>v.in.region method</h3>
+
 <div class="code"><pre>
 
 # In the source location, use v.in.region to generate a bounding box around the
@@ -292,7 +305,6 @@ location=source_location_name mapset=PERMANENT res=5 method=bicubic
   <li> <a href="http://www.mapref.org">MapRef -
       The Collection of Map Projections and Reference Systems for Europe</a> 
   <li> <a href="http://www.crs-geo.eu">Information and Service System for European Coordinate Reference Systems - CRS</a>
-  <li> <a href="http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html">Cartographical Map Projections</a> by Carlos A. Furuti
 </ul>
 
 <h2>SEE ALSO</h2>
@@ -317,7 +329,8 @@ The 'gdalwarp' and 'gdal_translate' utilities are available from the
 Martin Schroeder, University of Heidelberg, Germany<br>
 Man page text from S.J.D. Cox, AGCRC, CSIRO Exploration &amp; Mining, Nedlands, WA<br>
 Updated by <a href="mailto:morten@untamo.net">Morten Hulden</a><br>
-Datum transformation support and cleanup by Paul Kelly
+Datum transformation support and cleanup by Paul Kelly<br>
+Support of PROJ5+ by Markus Metz, <a href="https://www.mundialis.de">mundialis</a>
 
 <!--
 <p>

scripts/m.proj/m.proj.html

@@ -7,7 +7,7 @@ eastings and northings may be passed to the program directly from
 standard input. If the <b>output</b> option is omitted, the results
 are sent directly to standard output. In this way <em>m.proj</em> can
 be used as a simple frontend to
-the <a href="https://proj.org">PROJ</a>
+the <a href="https://proj.org/apps/cs2cs.html">PROJ</a>
 <em>cs2cs</em> utility. The <b>-i</b> or <b>-o</b> flags make the task
 especially easy for the common problem of converting to or from lat/long
 WGS84.
@@ -17,7 +17,9 @@ designed to determine the equivalent coordinate values of an
 individual position or list of
 positions. Use <em><a href="v.proj.html">v.proj</a></em> to reproject
 vector maps or <em><a href="r.proj.html">r.proj</a></em> for raster maps.
-
+<p>
+For an introduction to map projections (with PROJ),see the manual page of
+<a href="r.proj.html">r.proj</a>.
 
 <h2>NOTES</h2>
 

scripts/r.import/r.import.html

@@ -22,44 +22,54 @@ errors.
 
 <h3>Resolution</h3>
 
-<em>r.import</em> reports the estimated target resolution for each 
-input band. The estimated resolution will usually be some floating 
+<em>r.import</em> reports the estimated target resolution for each
+input band. The estimated resolution will usually be some floating
 point number, e.g. 271.301. In case option <b>resolution</b> is set to
 <em>estimated</em> (default), this floating point number will be used
-as target resolution. Since the target resolution should be typically the rounded 
+as target resolution. Since the target resolution should be typically the rounded
 estimated resolution, e.g. 250 or 300 instead of 271.301, flag <b>-e</b>
 can be used first to obtain the estimate without importing the raster bands.
-Then the desired resolution is set with option <b>resolution_value</b> 
+Then the desired resolution is set with option <b>resolution_value</b>
 and option <b>resolution</b>=<em>value</em>.
-For latlong locations, the resolution might be set to arc seconds, e.g. 1, 3, 7.5, 
+For latlong locations, the resolution might be set to arc seconds, e.g. 1, 3, 7.5,
 15, and 30 arc seconds are commonly used resolutions.
 
 <h3>Resampling methods</h3>
 
 When reprojecting a map to a new spatial reference system, the projected
 data is resampled with one of four different methods: nearest neighbor,
-bilinear, bicubic iterpolation or lanczos.
+bilinear, bicubic interpolation or lanczos.
 
 <p>
-In the following common use cases:
+In the following, common use cases are:
 <p>
-<b>nearest</b> is the simplest method and the only possible method for 
+<b>nearest</b> is the simplest method and the only possible method for
 categorical data.
 <p>
-<b>bilinear</b> does linear interpolation and provides smoother output 
-than <b>nearest</b>. <b>bilinear</b> is recommended when reprojecting a 
-DEM for hydrological analysis or for surfaces where overshoots must be 
-avoided, e.g. precipitation should not become negative. 
-<p> 
-<b>bicubic</b> produces smoother output than <b>bilinear</b>, at 
-the cost of overshoots. 
+<b>bilinear</b> does linear interpolation and provides smoother output
+than <b>nearest</b>. <b>bilinear</b> is recommended when reprojecting a
+DEM for hydrological analysis or for surfaces where overshoots must be
+avoided, e.g. precipitation should not become negative.
 <p>
-<b>lanczos</b> produces the smoothest output of all methods and 
-preserves contrast best. <b>lanczos</b> is recommended for imagery. 
-Both <b>bicubic</b> and <b>lanczos</b> preserve linear features. With 
-<b>nearest</b> or <b>bilinear</b>, linear features can become zigzag 
+<b>bicubic</b> produces smoother output than <b>bilinear</b>, at
+the cost of overshoots. Here, valid pixels that are adjacent to NULL pixels
+or edge pixels are set to NULL.
+<p>
+<b>lanczos</b> produces the smoothest output of all methods and
+preserves contrast best. <b>lanczos</b> is recommended for imagery.
+Both <b>bicubic</b> and <b>lanczos</b> preserve linear features. With
+<b>nearest</b> or <b>bilinear</b>, linear features can become zigzag
 features after reprojection.
-
+<p>
+In the bilinear, bicubic and lanczos methods, if any of the surrounding
+cells used to interpolate the new cell value are NULL, the resulting
+cell will be NULL, even if the nearest cell is not NULL. This will
+cause some thinning along NULL borders, such as the coasts of land
+areas in a DEM. The bilinear_f, bicubic_f and lanczos_f interpolation
+methods can be used if thinning along NULL edges is not desired.
+These methods &quot;fall back&quot; to simpler interpolation methods
+along NULL borders.  That is, from lanczos to bicubic to bilinear to
+nearest.
 <p>
 For explanation of the <b>-l</b> flag, please refer to the
 <a href="r.in.gdal.html">r.in.gdal</a> manual.
@@ -82,7 +92,7 @@ Example for North Carolina sample dataset (the tile name is "n35_w079_1arc_v3.ti
 <div class="code"><pre>
 # set computational region to e.g. 10m elevation model:
 g.region raster=elevation -p
- 
+
 # Import with reprojection on the fly. Recommended parameters:
 # resample   Resampling method to use for reprojection - bilinear
 # extent     Output raster map extent - region: extent of current region
@@ -100,7 +110,7 @@ r.colors srtmv3_resamp10m color=elevation
 Import of a subset from WorldClim <a href="http://worldclim.org/bioclim">Bioclim data set</a>,
 to be reprojected to current location projection (North Carolina sample dataset).
 Different resolutions are available, in this example we use the 2.5 arc-minutes
-resolution data. During import, we spatially subset the world data to the 
+resolution data. During import, we spatially subset the world data to the
 North Carolina region using the <em>extent</em> parameter:
 
 <div class="code"><pre>

scripts/r.import/r.import.py

@@ -8,7 +8,7 @@
 #
 # PURPOSE:      Import and reproject on the fly
 #
-# COPYRIGHT:    (C) 2015-2016 GRASS development team
+# COPYRIGHT:    (C) 2015-2021 GRASS development team
 #
 #               This program is free software under the GNU General
 #               Public License (>=v2). Read the file COPYING that

vector/v.proj/v.proj.html

@@ -8,6 +8,10 @@ corresponding PROJ_INFO files). The projection information is taken from the
 current PROJ_INFO files, as set and viewed with
 <em><a href="g.proj.html">g.proj</a></em>.
 
+<p>
+For an introduction to map projections (with PROJ),see the manual page of
+<a href="r.proj.html">r.proj</a>.
+
 <h2>NOTES</h2>
 
 If <b>output</b> is not specified it is set to be the same as input map
@@ -49,7 +53,9 @@ substantially deformed (straight lines become curves, squares become
 trapezoids, etc). The densification of linear features can help to avoid 
 topological errors.
 
-<h2>EXAMPLES</h2>
+<h2>EXAMPLE</h2>
+
+Reprojection of a vector map from another location and mapset into the current mapset:
 
 <div class="code"><pre>
 v.proj in=mymap location=latlong mapset=user1
@@ -77,7 +83,6 @@ v.proj in=mymap location=latlong mapset=user1
   <li> <a href="http://www.mapref.org">MapRef -
       The Collection of Map Projections and Reference Systems for Europe</a> 
   <li> <a href="http://www.crs-geo.eu">Information and Service System for European Coordinate Reference Systems - CRS</a>
-  <li> <a href="http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html">Cartographical Map Projections</a> by Carlos A. Furuti
 </ul>
 
 <h2>SEE ALSO</h2>