Setgridtype: docu update

doc/tex/mod/Setgrid

@@ -34,13 +34,15 @@ as the size of the target grid description.
 Sets the grid type of all input fields. The following grid types are available:
 @BeginList unstructured
 @Item = curvilinear
-Converts regular grid to curvilinear grid
+Converts a regular grid to a curvilinear grid
 @Item = unstructured
-Converts grid type to unstructured grid
+Converts a regular or curvilinear grid to an unstructured grid
 @Item = dereference
 Dereference a reference to a grid
 @Item = regular
-Converts reduced Gaussian grid to regular Gaussian grid
+Converts a reduced Gaussian grid to a regular Gaussian grid
+@Item = lonlat
+Converts a regular lonlat grid stored as a curvilinear grid back to a lonlat grid
 @EndList
 @EndDescription
 @EndOperator
@@ -62,7 +64,7 @@ the weights of each grid cell if needed by an operator, e.g. for @oper{fldmean}.
 @Item = grid
 STRING  Grid description file or name
 @Item = gridtype
-STRING  Grid type (curvilinear, unstructured, regular or dereference)
+STRING  Grid type (curvilinear, unstructured, regular, lonlat or dereference)
 @Item = gridarea
 STRING  Data file, the first field is used as grid cell area
 @EndParameter