Geografic-Information-System/scripts/r.tileset/r.tileset.html

<h2>DESCRIPTION</h2>

<em>r.tileset</em> generates sets of tiles in another projection that
cover a region in this projection with adequate resolution. By default
the current region and its resolution are used, the bounds and
resolution of another region can be used via the region option.


<h2>NOTES</h2>

<em>r.tileset</em> does not make "optimal" tilings (as few tiles of
the largest size less than the maximums). This means that from
latitude longitude projection to an appropriate projection for a
region, in the degenerate case, it may create tiles demanding up to
twice the necessary information. Furthermore, generating a tiling near
a divergant point of a source projection, such as the poles of a
cylindrical source projections, results in divergence of the tile set.
<p>
Not generating "optimal" tilings may have another consequence; the
aspect ratio of cells in the destination region will not necessarily
carry over to the source region and generated tiles may have cells of
strange aspect ratios. This might be a problem for some map request
services presenting data in an inappropriate projection or with strict
constraints on cell aspect ratio.


<h2>OUTPUT FORMAT</h2>

Each tile is listed on a separate line in the output. The lines are
formatted as follows:

<dl>
<dt>
<span class="code"><tt>
5|125|45|175|80|100
</tt></span>

<dd>This is the default output format. It is the tile's minimum x
coordinate, minimum y coordinate, maximum x coordinate, maximum y
coordinate, width in cells, and height in cells separated by the "|"
character. The fields can be separated by a different character by
changing the fs option.

<dt>
<span class="code"><tt>
w=5;s=125;e=45;n=175;cols=80;rows=100;
</tt></span>

<dd>This is output in a format convinent for setting variables in a shell
script.
<dt>
<span class="code"><tt>
bbox=5,125,45,175&amp;width=80&amp;height=100
</tt></span>

<dd>This is output in a format convinent for requesting data from some
http services.
</dl>


<h2>EXAMPLES</h2>

Generates tiles in latitude longitude that cover the current
region, each tile will be less than 1024 cells high and 2048 cells
across. The bounds and sizes of tiles in the output are separated by | (pipe):
<p>
<div class="code"><pre>
r.tileset sourceproj=+init=epsg:4326 maxrows=1024 maxcols=2048
</pre></div>

Generates tiles in latitude longitude projection that cover the
named region "ne-rio". The tiles will have 2 cells of overlap. The
output format will be strings like the bbox requests for WMS servers:
<p>
<div class="code"><pre>
r.tileset sourceproj=+init=epsg:4326 overlap=2 -w region=ne-rio
</pre></div>

Generates tiles in the projection of the location
"IrishGrid". Each tile will be less than 300x400 cells in size, with 3
cells of overlap in the top and right sides of each tile. The output
is in a format where each line is in shell script style. The
substitution <code>`g.proj -j location=IrishGrid`</code> will only
work in a unix style shell:
<p>
<div class="code"><pre>
r.tileset sourceproj="`g.proj -j location=IrishGrid`" maxrows=400 maxcols=300 overlap=3 -g
</pre></div>

<h2>KNOWN ISSUES</h2>

<ul>
<li><em>r.tileset</em> does not know about meridians that
"wrap-around" in projections.</li>
</ul>


<h2>AUTHORS</h2>

Cedric Shock<br>
Updated for GRASS 7 by Martin Landa, CTU in Prague, Czech Republic

<p>
<i>Last changed: $Date$</i>