if ( g is "CAVOK") {
    rename(g,cavok); 
    group g : dump; non_alpha na;
		constant isCavok=1;
		constant ceilingAndVisibilityOK="true";
		constant cavokOrVisibility=1;
} else {
		constant ceilingAndVisibilityOK="false";
		constant isCavok=0;
		if (g is "//" || g is "///" || g is "////" || g is "/////" || g is "//////") {
				rename(g,missingVisibilityField1);
				group g : dump; non_alpha na;
		} 
		if (g is "//" || g is "///" || g is "////" || g is "/////" || g is "//////") {
				rename(g,missingVisibilityField2);
				group g : dump; non_alpha na;
		} 
		if (substr(g,-3,3) is "NDV" || is_integer(g,0,4)  ) {
				rename(g,visibilityInMetres);
		    group g : dump; non_alpha na;
				if (is_integer(visibilityInMetres,0,4)) {
						visibility=to_integer(visibilityInMetres,0,4);
						constant cavokOrVisibility=1;
				}
		}
		if (g is "NDV") {
				rename(g,ndv);
				modify ndv : hidden;
		    group g : dump; non_alpha na;
		}
		if (substr(g,-2,2) is "KM"  ) {
				rename(g,visibilityInKM);
		    group g : dump; non_alpha na;
				#visibilityInKilometres=to_integer(visibilityInKM,0);
				#meta visibility evaluate(visibilityInKilometres * 1000);
		}
		if (is_integer(g,0,1)) {
				rename(g,visibilityInteger);
		    group g : dump; non_alpha na;
		} 
		if (substr(g, -2 ,2) is "SM" ) {
        rename(g,visibilityInStatuteMiles);
        group g : dump; non_alpha na;
		}
		if ( ( substr(g,4,1) is "N" || substr(g,4,1) is "S" || substr(g,4,1) is "E" || substr(g,4,1) is "W" 
				||
				substr(g,4,2) is "NE" || substr(g,4,2) is "SE" || substr(g,4,2) is "NW" || substr(g,4,2) is "SW" 
				||
				substr(g,4,1) is "/" )
				&&
				is_integer(g,0,4)
				) {
				rename(g,directionalVariationInVisibility);
				group g : dump; non_alpha na;
				variationOfVisibility=to_integer(directionalVariationInVisibility);
				if (length(directionalVariationInVisibility) == 5) {
						directionOfVariation=to_string(directionalVariationInVisibility,4,1);
				} else {
						directionOfVariation=to_string(directionalVariationInVisibility,4,2);
				}
				variationOfVisibilityDirection=dict_search("metar/direction.table",directionOfVariation,1) : string_type;
				variationOfVisibilityDirectionAngle=dict_search("metar/direction.table",directionOfVariation,2) ;
		}
		include "metar/rvr1.def";
		include "metar/rvr2.def";
		include "metar/rvr3.def";
		include "metar/rvr4.def";
}