Clairfy description of reflectance_as_intensity.

Close #2250

doc/stages/readers.rxp.rst

@@ -6,28 +6,35 @@ readers.rxp
 The **RXP reader** read from files in the RXP format, the in-house streaming format used by `RIEGL Laser Measurement Systems GmbH`_.
 
 .. warning::
-   This software has not been developed by RIEGL, and RIEGL will not provide any support for this driver.
-   Please do not contact RIEGL with any questions or issues regarding this driver.
-   RIEGL is not responsible for damages or other issues that arise from use of this driver.
-   This driver has been tested against RiVLib version 1.39 on a Ubuntu 14.04 using gcc43.
+   This software has not been developed by RIEGL, and RIEGL will not provide
+   any support for this driver.  Please do not contact RIEGL with any
+   questions or issues regarding this driver.  RIEGL is not responsible
+   for damages or other issues that arise from use of this driver.
+   This driver has been tested against RiVLib version 1.39 on a Ubuntu
+   14.04 using gcc43.
 
 .. plugin::
 
 Installation
 ------------
 
-To build PDAL with rxp support, set RiVLib_DIR to the path of your local RiVLib installation.
-RiVLib can be obtained from the `RIEGL download pages`_ with a properly enabled user account.
-The RiVLib files do not need to be in a system-level directory, though they could be (e.g. they could be in ``/usr/local``, or just in your home directory somewhere).
-For help building PDAL with optional libraries, see `the optional library documentation`_.
+To build PDAL with rxp support, set RiVLib_DIR to the path of your local
+RiVLib installation.  RiVLib can be obtained from the `RIEGL download pages`_
+with a properly enabled user account.  The RiVLib files do not need to be
+in a system-level directory, though they could be (e.g. they could be
+in ``/usr/local``, or just in your home directory somewhere).  For help
+building PDAL with optional libraries, see
+`the optional library documentation`_.
 
 
 Example
 -------
 
-This example rescales the points, given in the scanner's own coordinate system, to values that can be written to a las file.
-Only points with a valid gps time, as determined by a pps pulse, are read from the rxp, since the ``sync_to_pps`` option is "true".
-Reflectance values are mapped to intensity values using sensible defaults.
+This example rescales the points, given in the scanner's own coordinate
+system, to values that can be written to a las file.  Only points with a
+valid gps time, as determined by a pps pulse, are read from the rxp, since
+the ``sync_to_pps`` option is "true".  Reflectance values are mapped to
+intensity values using sensible defaults.
 
 .. code-block:: json
 
@@ -48,9 +55,11 @@ Reflectance values are mapped to intensity values using sensible defaults.
     }
 
 
-We set the ``discard_high_return_numbers`` option to ``true`` on the :ref:`writers.las`.
-RXP files can contain more returns per shot than is supported by las, and so we need to explicitly tell the las writer to ignore those high return number points.
-You could also use :ref:`filters.python` to filter those points earlier in the pipeline.
+We set the ``discard_high_return_numbers`` option to ``true`` on the
+:ref:`writers.las`.  RXP files can contain more returns per shot than is
+supported by las, and so we need to explicitly tell the las writer to ignore
+those high return number points.  You could also use :ref:`filters.python`
+to filter those points earlier in the pipeline.
 
 
 Options
@@ -63,18 +72,24 @@ rdtp
   Boolean to switch from file-based reading to RDTP-based. [default: false]
 
 sync_to_pps
-  If "true", ensure all incoming points have a valid pps timestamp, usually provided by some sort of GPS clock.
-  If "false", use the scanner's internal time.
+  If "true", ensure all incoming points have a valid pps timestamp, usually
+  provided by some sort of GPS clock.  If "false", use the scanner's internal
+  time.
   [default: true]
 
 minimal
   If "true", only write X, Y, Z, and time values to the data stream.
   If "false", write all available values as derived from the rxp file.
-  Use this feature to reduce the memory footprint of a PDAL run, if you don't need any values but the points themselves.
+  Use this feature to reduce the memory footprint of a PDAL run, if you
+  don't need any values but the points themselves.
   [default: false]
 
 reflectance_as_intensity
-  If "true", maps reflectance values onto intensity values using a range from -25dB to 5dB.
+  If "true", in addition to storing reflectance values directly, also
+  stores the values as Intensity by mapping the reflectance values in the
+  range from `min_reflectance` to `max_reflectance` to the range 0-65535.
+  Values less than `min_reflectance` are assigned the value 0.
+  Values greater `max_reflectance` are assigned the value 65535.
   [default: true]
 
 min_reflectance