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<li class="toctree-l2"><a class="reference internal" href="#introduction">Introduction</a><ul>
<li class="toctree-l3"><a class="reference internal" href="#simple-example">Simple Example</a></li>
<li class="toctree-l3"><a class="reference internal" href="#reprojection-example">Reprojection Example</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#pipeline-array">Pipeline Array</a></li>
<li class="toctree-l3"><a class="reference internal" href="#stage-objects">Stage Objects</a></li>
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<li class="toctree-l2"><a class="reference internal" href="#extended-examples">Extended Examples</a><ul>
<li class="toctree-l3"><a class="reference internal" href="#bpf-to-las">BPF to LAS</a></li>
<li class="toctree-l3"><a class="reference internal" href="#python-hag">Python HAG</a></li>
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<div class="section" id="pipeline">
<span id="id1"></span><h1>Pipeline<a class="headerlink" href="#pipeline" title="Permalink to this headline">¶</a></h1>
<p>Pipelines are the operative construct in PDAL, and it is how data are modeled
from reading, processing, and writing. PDAL internally constructs a pipeline to
perform data translation operations using <a class="reference internal" href="apps/translate.html#translate-command"><span class="std std-ref">translate</span></a>, for
example. While specific <a class="reference internal" href="apps/index.html#apps"><span class="std std-ref">applications</span></a> are useful in many contexts,
a pipeline provides useful advantages for more complex things:</p>
<ol class="arabic simple">
<li>You have a record of the operation(s) applied to the data</li>
<li>You can construct a skeleton of an operation and substitute specific
options (filenames, for example)</li>
<li>You can construct complex operations using the <a class="reference external" href="http://www.json.org/">JSON</a> manipulation
facilities of whatever language you want.</li>
</ol>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last"><a class="reference internal" href="apps/pipeline.html#pipeline-command"><span class="std std-ref">pipeline</span></a> is used to invoke pipeline operations
via the command line.</p>
</div>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">As of PDAL 1.2, <a class="reference external" href="http://www.json.org/">JSON</a> is the preferred specification language
for PDAL pipelines. XML was dropped at the 1.6 release.</p>
</div>
<div class="section" id="introduction">
<h2>Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline">¶</a></h2>
<p>A JSON object represents a PDAL processing pipeline. The structure is always a
JSON object, with the primary object called <code class="docutils literal"><span class="pre">pipeline</span></code> being an array of
inferred or explicit PDAL <a class="reference internal" href="#stage-object"><span class="std std-ref">Stage Objects</span></a> representations.</p>
<div class="section" id="simple-example">
<h3>Simple Example<a class="headerlink" href="#simple-example" title="Permalink to this headline">¶</a></h3>
<p>A simple PDAL pipeline, inferring the appropriate drivers for the reader and
writer from filenames, and able to be specified as a set of sequential steps:</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="s2">"input.las"</span><span class="p">,</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"crop"</span><span class="p">,</span>
<span class="nt">"bounds"</span><span class="p">:</span><span class="s2">"([0,100],[0,100])"</span>
<span class="p">},</span>
<span class="s2">"output.bpf"</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="figure" id="id3">
<img alt="_images/las-crop-bpf-pipeline.png" src="_images/las-crop-bpf-pipeline.png" />
<p class="caption"><span class="caption-text">A simple pipeline to convert <a class="reference internal" href="stages/readers.las.html#readers-las"><span class="std std-ref">LAS</span></a> to <a class="reference internal" href="stages/readers.bpf.html#readers-bpf"><span class="std std-ref">BPF</span></a>
while only keeping points inside the box <span class="math">\([0 \leq x \leq 100, 0 \leq y \leq 100]\)</span>.</span></p>
</div>
</div>
<div class="section" id="reprojection-example">
<h3>Reprojection Example<a class="headerlink" href="#reprojection-example" title="Permalink to this headline">¶</a></h3>
<p>A more complex PDAL pipeline reprojects the stage tagged <code class="docutils literal"><span class="pre">A1</span></code>, merges
the result with <code class="docutils literal"><span class="pre">B</span></code>, and writes the merged output to a GeoTIFF file
with the <a class="reference internal" href="stages/writers.gdal.html#writers-gdal"><span class="std std-ref">writers.gdal</span></a> writer:</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"A.las"</span><span class="p">,</span>
<span class="nt">"spatialreference"</span><span class="p">:</span><span class="s2">"EPSG:26916"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"filters.reprojection"</span><span class="p">,</span>
<span class="nt">"in_srs"</span><span class="p">:</span><span class="s2">"EPSG:26916"</span><span class="p">,</span>
<span class="nt">"out_srs"</span><span class="p">:</span><span class="s2">"EPSG:4326"</span><span class="p">,</span>
<span class="nt">"tag"</span><span class="p">:</span><span class="s2">"A2"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"B.las"</span><span class="p">,</span>
<span class="nt">"tag"</span><span class="p">:</span><span class="s2">"B"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"filters.merge"</span><span class="p">,</span>
<span class="nt">"tag"</span><span class="p">:</span><span class="s2">"merged"</span><span class="p">,</span>
<span class="nt">"inputs"</span><span class="p">:[</span>
<span class="s2">"A2"</span><span class="p">,</span>
<span class="s2">"B"</span>
<span class="p">]</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"writers.gdal"</span><span class="p">,</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"output.tif"</span>
<span class="p">}</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="figure" id="id4">
<img alt="_images/reproject-merge-pipeline.png" src="_images/reproject-merge-pipeline.png" />
<p class="caption"><span class="caption-text">A more complex pipeline that merges two inputs together but uses
<a class="reference internal" href="stages/filters.reprojection.html#filters-reprojection"><span class="std std-ref">filters.reprojection</span></a> to transform the coordinate system of
file <code class="docutils literal"><span class="pre">B.las</span></code> from <a class="reference external" href="http://spatialreference.org/ref/epsg/nad83-utm-zone-16n/">UTM</a> to <a class="reference external" href="http://spatialreference.org/ref/epsg/4326/">Geographic</a>.</span></p>
</div>
</div>
</div>
<div class="section" id="pipeline-objects">
<h2>Pipeline Objects<a class="headerlink" href="#pipeline-objects" title="Permalink to this headline">¶</a></h2>
<p>PDAL JSON pipelines always consist of a single object. This object (referred to
as the PDAL JSON object below) represents a processing pipeline.</p>
<ul class="simple">
<li>The PDAL JSON object may have any number of members (name/value pairs).</li>
<li>The PDAL JSON object must have a <a class="reference internal" href="#pipeline-array"><span class="std std-ref">Pipeline Array</span></a>.</li>
</ul>
<div class="section" id="pipeline-array">
<span id="id2"></span><h3>Pipeline Array<a class="headerlink" href="#pipeline-array" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>The pipeline array may have any number of string or <a class="reference internal" href="#stage-object"><span class="std std-ref">Stage Objects</span></a>
elements.</li>
<li>String elements shall be interpreted as filenames. PDAL will attempt to infer
the proper driver from the file extension and position in the array. A writer
stage will only be created if the string is the final element in the array.</li>
</ul>
</div>
<div class="section" id="stage-objects">
<span id="stage-object"></span><h3>Stage Objects<a class="headerlink" href="#stage-objects" title="Permalink to this headline">¶</a></h3>
<p>For more on PDAL stages and their options, check the PDAL documentation on
<a class="reference internal" href="stages/readers.html#readers"><span class="std std-ref">Readers</span></a>, <a class="reference internal" href="stages/writers.html#writers"><span class="std std-ref">Writers</span></a>, and <a class="reference internal" href="stages/filters.html#filters"><span class="std std-ref">Filters</span></a>.</p>
<ul class="simple">
<li>A stage object may have a member with the name <code class="docutils literal"><span class="pre">tag</span></code> whose value is a
string. The purpose of the tag is to cross-reference this stage within other
stages. Each <code class="docutils literal"><span class="pre">tag</span></code> must be unique.</li>
<li>A stage object may have a member with the name <code class="docutils literal"><span class="pre">inputs</span></code> whose value is an
array of strings. Each element in the array is the tag of another stage to be
set as input to the current stage.</li>
<li>Reader stages will disregard the <code class="docutils literal"><span class="pre">inputs</span></code> member.</li>
<li>If <code class="docutils literal"><span class="pre">inputs</span></code> is not specified for the first non-reader stage, all reader
stages leading up to the current stage will be used as inputs.</li>
<li>If <code class="docutils literal"><span class="pre">inputs</span></code> is not specified for any subsequent non-reader stages, the
previous stage in the array will be used as input.</li>
<li>A <code class="docutils literal"><span class="pre">tag</span></code> mentioned in another stage’s <code class="docutils literal"><span class="pre">inputs</span></code> must have been previously
defined in the <code class="docutils literal"><span class="pre">pipeline</span></code> array.</li>
<li>A reader or writer stage object may have a member with the name <code class="docutils literal"><span class="pre">type</span></code> whose
value is a string. The <code class="docutils literal"><span class="pre">type</span></code> must specify a valid PDAL reader or writer
name.</li>
<li>A filter stage object must have a member with the name <code class="docutils literal"><span class="pre">type</span></code> whose value is
a string. The <code class="docutils literal"><span class="pre">type</span></code> must specify a valid PDAL filter name.</li>
<li>A stage object may have additional members with names corresponding to
stage-specific option names and their respective values. Values provided as
JSON objects or arrays will be stringified and parsed within the stage.</li>
<li>Applications can place a <code class="docutils literal"><span class="pre">user_data</span></code> node on any stage object and it will be
carried through to any serialized pipeline output.</li>
</ul>
</div>
<div class="section" id="filename-globbing">
<h3>Filename Globbing<a class="headerlink" href="#filename-globbing" title="Permalink to this headline">¶</a></h3>
<ul class="simple">
<li>A filename may contain the wildcard character <code class="docutils literal"><span class="pre">*</span></code> to match any string of
characters. This can be useful if working with multiple input files in a
directory (e.g., merging all files).</li>
</ul>
</div>
</div>
<div class="section" id="extended-examples">
<h2>Extended Examples<a class="headerlink" href="#extended-examples" title="Permalink to this headline">¶</a></h2>
<div class="section" id="bpf-to-las">
<h3>BPF to LAS<a class="headerlink" href="#bpf-to-las" title="Permalink to this headline">¶</a></h3>
<p>The following pipeline converts the input file from <a class="reference internal" href="stages/readers.bpf.html#readers-bpf"><span class="std std-ref">BPF</span></a> to
<a class="reference internal" href="stages/writers.las.html#writers-las"><span class="std std-ref">LAS</span></a>, inferring both the reader and writer type, and
setting a number of options on the writer stage.</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="s2">"utm15.bpf"</span><span class="p">,</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"out2.las"</span><span class="p">,</span>
<span class="nt">"scale_x"</span><span class="p">:</span><span class="mf">0.01</span><span class="p">,</span>
<span class="nt">"offset_x"</span><span class="p">:</span><span class="mf">311898.23</span><span class="p">,</span>
<span class="nt">"scale_y"</span><span class="p">:</span><span class="mf">0.01</span><span class="p">,</span>
<span class="nt">"offset_y"</span><span class="p">:</span><span class="mf">4703909.84</span><span class="p">,</span>
<span class="nt">"scale_z"</span><span class="p">:</span><span class="mf">0.01</span><span class="p">,</span>
<span class="nt">"offset_z"</span><span class="p">:</span><span class="mf">7.385474</span>
<span class="p">}</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="python-hag">
<h3>Python HAG<a class="headerlink" href="#python-hag" title="Permalink to this headline">¶</a></h3>
<p>In our next example, the reader and writer types are once again inferred. After
reading the input file, the ferry filter is used to copy the Z dimension into a
new height above ground (HAG) dimension. Next, the <a class="reference internal" href="stages/filters.python.html#filters-python"><span class="std std-ref">filters.python</span></a>
is used with a Python script to compute height above ground values by comparing
the Z values to a surface model. These height above ground values are then
written back into the Z dimension for further analysis. See the Python
code at <a class="reference external" href="https://raw.githubusercontent.com/PDAL/PDAL/master/test/data/autzen/hag.py.in">hag.py</a>.</p>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<p class="last"><a class="reference internal" href="stages/filters.hag.html#filters-hag"><span class="std std-ref">filters.hag</span></a> describes using a specific filter to do
this job in more detail.</p>
</div>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="s2">"autzen.las"</span><span class="p">,</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"ferry"</span><span class="p">,</span>
<span class="nt">"dimensions"</span><span class="p">:</span><span class="s2">"Z=HAG"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"filters.python"</span><span class="p">,</span>
<span class="nt">"script"</span><span class="p">:</span><span class="s2">"hag.py"</span><span class="p">,</span>
<span class="nt">"function"</span><span class="p">:</span><span class="s2">"filter"</span><span class="p">,</span>
<span class="nt">"module"</span><span class="p">:</span><span class="s2">"anything"</span>
<span class="p">},</span>
<span class="s2">"autzen-hag.las"</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="dtm">
<h3>DTM<a class="headerlink" href="#dtm" title="Permalink to this headline">¶</a></h3>
<p>A common task is to create a digital terrain model (DTM) from the input point
cloud. This pipeline infers the reader type, applies an approximate ground
segmentation filter using <a class="reference internal" href="stages/filters.pmf.html#filters-pmf"><span class="std std-ref">filters.pmf</span></a>, filters out all points but the
ground returns (classification value of 2) using the <a class="reference internal" href="stages/filters.range.html#filters-range"><span class="std std-ref">filters.range</span></a>, and
then creates the DTM using the <a class="reference internal" href="stages/writers.gdal.html#writers-gdal"><span class="std std-ref">writers.gdal</span></a>.</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="s2">"autzen-full.las"</span><span class="p">,</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"ground"</span><span class="p">,</span>
<span class="nt">"approximate"</span><span class="p">:</span><span class="kc">true</span><span class="p">,</span>
<span class="nt">"max_window_size"</span><span class="p">:</span><span class="mi">33</span><span class="p">,</span>
<span class="nt">"slope"</span><span class="p">:</span><span class="mf">1.0</span><span class="p">,</span>
<span class="nt">"max_distance"</span><span class="p">:</span><span class="mf">2.5</span><span class="p">,</span>
<span class="nt">"initial_distance"</span><span class="p">:</span><span class="mf">0.15</span><span class="p">,</span>
<span class="nt">"cell_size"</span><span class="p">:</span><span class="mf">1.0</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"range"</span><span class="p">,</span>
<span class="nt">"limits"</span><span class="p">:</span><span class="s2">"Classification[2:2]"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"writers.gdal"</span><span class="p">,</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"autzen-surface.tif"</span><span class="p">,</span>
<span class="nt">"output_type"</span><span class="p">:</span><span class="s2">"min"</span><span class="p">,</span>
<span class="nt">"output_format"</span><span class="p">:</span><span class="s2">"tif"</span><span class="p">,</span>
<span class="nt">"grid_dist_x"</span><span class="p">:</span><span class="mf">1.0</span><span class="p">,</span>
<span class="nt">"grid_dist_y"</span><span class="p">:</span><span class="mf">1.0</span>
<span class="p">}</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="decimate-colorize">
<h3>Decimate & Colorize<a class="headerlink" href="#decimate-colorize" title="Permalink to this headline">¶</a></h3>
<p>This example still infers the reader and writer types while applying options on
both. The pipeline decimates the input LAS file by keeping every other point,
and then colorizes the points using the provided raster image. The output is
written as ASCII text.</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"1.2-with-color.las"</span><span class="p">,</span>
<span class="nt">"spatialreference"</span><span class="p">:</span><span class="s2">"EPSG:2993"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"decimation"</span><span class="p">,</span>
<span class="nt">"step"</span><span class="p">:</span><span class="mi">2</span><span class="p">,</span>
<span class="nt">"offset"</span><span class="p">:</span><span class="mi">1</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"colorization"</span><span class="p">,</span>
<span class="nt">"raster"</span><span class="p">:</span><span class="s2">"autzen.tif"</span><span class="p">,</span>
<span class="nt">"dimensions"</span><span class="p">:</span><span class="s2">"Red:1:1, Green:2:1, Blue:3:1"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"junk.txt"</span><span class="p">,</span>
<span class="nt">"delimiter"</span><span class="p">:</span><span class="s2">","</span><span class="p">,</span>
<span class="nt">"write_header"</span><span class="p">:</span><span class="kc">false</span>
<span class="p">}</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="merge-reproject">
<h3>Merge & Reproject<a class="headerlink" href="#merge-reproject" title="Permalink to this headline">¶</a></h3>
<p>Our first example with multiple readers, this pipeline infers the reader types,
and assigns spatial reference information to each. Next, the
<a class="reference internal" href="stages/filters.merge.html#filters-merge"><span class="std std-ref">filters.merge</span></a> merges points from all previous readers, and the
<a class="reference internal" href="stages/filters.reprojection.html#filters-reprojection"><span class="std std-ref">filters.reprojection</span></a> filter reprojects data to the specified output
spatial reference system.</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"1.2-with-color.las"</span><span class="p">,</span>
<span class="nt">"spatialreference"</span><span class="p">:</span><span class="s2">"EPSG:2027"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"filename"</span><span class="p">:</span><span class="s2">"1.2-with-color.las"</span><span class="p">,</span>
<span class="nt">"spatialreference"</span><span class="p">:</span><span class="s2">"EPSG:2027"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"filters.merge"</span>
<span class="p">},</span>
<span class="p">{</span>
<span class="nt">"type"</span><span class="p">:</span><span class="s2">"reprojection"</span><span class="p">,</span>
<span class="nt">"out_srs"</span><span class="p">:</span><span class="s2">"EPSG:2028"</span>
<span class="p">}</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="globbed-inputs">
<h3>Globbed Inputs<a class="headerlink" href="#globbed-inputs" title="Permalink to this headline">¶</a></h3>
<p>Finally, we capture another merge pipeline demonstrating the ability to glob
multiple input LAS files from a given directory.</p>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="s2">"/path/to/data/\*.las"</span><span class="p">,</span>
<span class="s2">"output.las"</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<p class="last">The PDAL source tree contains a number of example pipelines that
are used for testing. You might find these inspiring. Go to
<a class="reference external" href="https://github.com/PDAL/PDAL/tree/master/test/data/pipeline">https://github.com/PDAL/PDAL/tree/master/test/data/pipeline</a> to find
more.</p>
</div>
</div>
</div>
<div class="section" id="api-considerations">
<h2>API Considerations<a class="headerlink" href="#api-considerations" title="Permalink to this headline">¶</a></h2>
<p>A <cite>Pipeline</cite> is composed as an array of <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Stage</span></code> , with the
first stage at the beginning and the last at the end. There are two primary
building blocks in PDAL, <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Stage</span></code> and
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::PointView</span></code>. <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Reader</span></code>,
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Writer</span></code>, and <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Filter</span></code> are all subclasses of
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Stage</span></code>.</p>
<p><code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::PointView</span></code> is the substrate that flows between stages in a
pipeline and transfers the actual data as it moves through the pipeline. A
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::PointView</span></code> contains a <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::PointTablePtr</span></code>, which
itself contains a list of <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Dimension</span></code> objects that define the
actual channels that are stored in the <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::PointView</span></code>.</p>
<p>PDAL provides four types of stages – <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Reader</span></code>,
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Writer</span></code>, <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Filter</span></code>, and
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::MultiFilter</span></code> – with the latter being hardly used (just
<a class="reference internal" href="stages/filters.merge.html#filters-merge"><span class="std std-ref">filters.merge</span></a>) at this point. A Reader is a producer of data, a Writer
is a consumer of data, and a Filter is an actor on data.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">As a C++ API consumer, you are generally not supposed to worry about the underlying
storage of the PointView, but there might be times when you simply just
“want the data.” In those situations, you can use the
<code class="xref cpp cpp-func docutils literal"><span class="pre">pdal::PointView::getBytes()</span></code> method to stream out the raw storage.</p>
</div>
<div class="section" id="usage">
<h3>Usage<a class="headerlink" href="#usage" title="Permalink to this headline">¶</a></h3>
<p>While pipeline objects are manipulable through C++ objects, the other, more
convenient way is through an JSON syntax. The JSON syntax mirrors the
arrangement of the Pipeline, with options and auxiliary metadata added on a
per-stage basis.</p>
<p>We have two use cases specifically in mind:</p>
<ul class="simple">
<li>a <a class="reference internal" href="apps/pipeline.html#pipeline-command"><span class="std std-ref">command-line</span></a> application that reads an JSON
file to allow a user to easily construct arbitrary writer pipelines, as
opposed to having to build applications custom to individual needs with
arbitrary options, filters, etc.</li>
<li>a user can provide JSON for a reader pipeline, construct it via a simple call
to the PipelineManager API, and then use the <code class="xref cpp cpp-func docutils literal"><span class="pre">pdal::Stage::read()</span></code>
function to perform the read and then do any processing of the points. This
style of operation is very appropriate for using PDAL from within
environments like Python where the focus is on just getting the points, as
opposed to complex pipeline construction.</li>
</ul>
<div class="highlight-json"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="nt">"pipeline"</span><span class="p">:[</span>
<span class="s2">"/path/to/my/file/input.las"</span><span class="p">,</span>
<span class="s2">"output.las"</span>
<span class="p">]</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last"><a class="reference external" href="https://github.com/PDAL/PDAL/blob/master/test/data/pipeline/">https://github.com/PDAL/PDAL/blob/master/test/data/pipeline/</a> contains
test suite pipeline files that provide an excellent example of the
currently possible operations.</p>
</div>
</div>
<div class="section" id="stage-types">
<h3>Stage Types<a class="headerlink" href="#stage-types" title="Permalink to this headline">¶</a></h3>
<p><code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Reader</span></code>, <code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Writer</span></code>, and
<code class="xref cpp cpp-class docutils literal"><span class="pre">pdal::Filter</span></code> are the C++ classes that define the stage types in
PDAL. Readers follow the pattern of <a class="reference internal" href="stages/readers.las.html#readers-las"><span class="std std-ref">readers.las</span></a> or
<a class="reference internal" href="stages/readers.oci.html#readers-oci"><span class="std std-ref">readers.oci</span></a>, Writers follow the pattern of <a class="reference internal" href="stages/writers.las.html#writers-las"><span class="std std-ref">writers.las</span></a> or
<a class="reference internal" href="stages/readers.oci.html#readers-oci"><span class="std std-ref">readers.oci</span></a>, with Filters using <a class="reference internal" href="stages/filters.reprojection.html#filters-reprojection"><span class="std std-ref">filters.reprojection</span></a> or
<a class="reference internal" href="stages/filters.crop.html#filters-crop"><span class="std std-ref">filters.crop</span></a>.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last"><a class="reference internal" href="stages/index.html#stage-index"><span class="std std-ref">Readers, Writers, and Filters</span></a> contains a full listing of possible stages and
descriptions of their options.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Issuing the command <code class="docutils literal"><span class="pre">pdal</span> <span class="pre">info</span> <span class="pre">--options</span></code> will list all available
stages and their options. See <a class="reference internal" href="apps/info.html#info-command"><span class="std std-ref">info</span></a> for more.</p>
</div>
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