my $distance = sqrt(
                ($nav{$numilines % 2}{"x"}{int($thisx)} -
                 $nav{$numilines % 2}{"x"}{int($prevx)}) **2 +
                ($nav{$numilines % 2}{"y"}{int($thisx)}
                 $nav{$numilines % 2}{"y"}{int($prevx)}) **2
                );