+ $default_of{$sector->towernum} = $sector->sectornum
+ if $sector->sectorname eq '_default';
+ }
+}
+foreach my $towernum (keys %sectors_of) {
+ # hide default sectors for towers that have real sectors defined
+ my $sectornum = $default_of{$towernum};
+ if ( keys %{ $sectors_of{$towernum} } > 1 ) {
+ delete $sectors_of{$towernum}->{$sectornum};
+ delete $sectors_of{''}->{$sectornum};
+ }
+ else {
+ # show default sectorname as '(all)'
+ $sectors_of{$towernum}->{$sectornum} = '(all)'