Added COPY documentation

meteoio/IOHandler.cc

@@ -40,6 +40,15 @@ namespace mio {
  * - \subpage pgmio "PGMIO" for reading PGM grid files (no extra requirements)
  * - \subpage smetio "SMETIO" for reading SMET meteo data files (no extra requirements)
  *
+ * @section data_generators Data generators
+ * It is also possible to duplicate a meteorological parameter as another meteorological parameter. This is done by specifying a COPY key, following the syntax
+ * COPY::new_name = existing_parameter. For example:
+ * @code
+ * COPY::VW_avg = VW
+ * @endcode
+ * This creates a new parameter VW_avg that starts as an exact copy of the raw data of VW, for each station. This newly created parameter is
+ * then processed as any other meteorological parameter (thus going through filtering, generic processing, spatial interpolations). This only current
+ * limitation is that the parameter providing the raw data must be defined for all stations (even if filled with nodata, this is good enough).
  */
 
 void IOHandler::registerPlugins()

meteoio/MainPage.h

@@ -161,7 +161,8 @@ namespace mio {
  *             (key=SPECIALPTS), one for data assimilation (key=DA), one for landuse (key=LANDUSE) and one for Digital
  *             Elevation Model (key=DEM). Please see \ref plugins for the available plugins. Afterwards, each plugin comes
  *             with its own set of keys, as specified in the plugin's documentation. Morevover, the geographic coordinate
- *             system should often be specified, as explained in \ref coords .
+ *             system should often be specified, as explained in \ref coords. For the meteorological parameters, it is also
+ *             possible to copy one parameter into a new one, as shown in \ref data_generators.
  *
  *  - [Output] : This section is very similar to the [Input] section, but (obviously) for outputing the data.
  *