@BeginModule
@Name      = Gridcell
@Title     = Grid cell quantities
@Section   = Miscellaneous
@Arguments = ifile ofile
@Operators = gridarea gridweights

@BeginDescription
This module reads the grid cell area of the first grid from the input stream.
If the grid cell area is missing it will be computed from the 
grid description. Depending on the chosen operator the grid cell area or weights
are written to the output stream.
@EndDescription
@EndModule


@BeginOperator_gridarea
@Title     = Grid cell area

@BeginDescription
Writes the grid cell area to the output stream. If the grid cell area have to
be computed it is scaled with the earth radius to square meters.
@EndDescription
@EndOperator

@BeginOperator_gridweights
@Title     = Grid cell weights

@BeginDescription
Writes the grid cell area weights to the output stream.
@EndDescription
@EndOperator


@BeginEnvironment
@Item = PLANET_RADIUS
This variable is used to scale the computed grid cell areas to square meters. 
By default PLANET_RADIUS is set to an earth radius of 6371000 meter.
@EndEnvironment

