Robin subwindow density/quality calculations

The ROBIN_CORRECTED_DENSITY and ROBIN_CORRECTED_QUALITY are calculated according to the following function :

 sub Quantify_ROBIN
 {

   my ($whole_window, $sub_window, $correction_level, $radar_name, $beam_name, $window, $log) = @_;
   my $ROB_density = 0;
   my $ROB_quality = 0;
   my $ROB_cor_level = undef;
   my $ClutPerc = 25;

   my ($radar) = $radar_name =~ /RP-(\w{3})/;
   my ($beam) = $beam_name =~ /BEAM_(\d+)/; 
   $beam = 'B' . $beam;
   my $key = $radar . '_' . $beam . '_' . $window;

   my %DEFAULT_VALUES = (
   GLO_B1_SE => { cthresh         => 1864,
                  defReflectivity => 3033,
                  defClut         => 18.65,
                  CP              => 15
                },
   GLO_B1_NW => { cthresh         => 1864,
                  defReflectivity => 901,
                  defClut         => 15.05,
                  CP              => 15
                },
   GLO_B2_SE => { cthresh         => 1804,
                  defReflectivity => 527,
                  defClut         => 3.33,
                  CP              => 15
                },
   GLO_B2_NW => { cthresh         => 1804,
                  defReflectivity => 44,
                  defClut         => 1.28,
                  CP              => 15
                },

   WIE_B1_SE => { cthresh         => 310,
                  defReflectivity => 0,
                  defClut         => 0,
                  CP              => 15
                },
   WIE_B1_NW => { cthresh         => 310,
                  defReflectivity => 0,
                  defClut         => 0,
                  CP              => 15
                },
   WIE_B2_SE => { cthresh         => 594,
                  defReflectivity => 0,
                  defClut         => 0,
                  CP              => 15
                },
   WIE_B2_NW => { cthresh         => 594,
                  defReflectivity => 0,
                  defClut         => 0,
                  CP              => 15
                },
 );

 my $cthresh         = 0;
 my $defReflectivity = 0;
 my $defClut         = 0;
 my $CP              = 0;

 if(exists($DEFAULT_VALUES{$key})) {
   $cthresh         = $DEFAULT_VALUES{$key}->{cthresh};
   $defReflectivity = $DEFAULT_VALUES{$key}->{defReflectivity};
   $defClut         = $DEFAULT_VALUES{$key}->{defClut};
   $CP              = $DEFAULT_VALUES{$key}->{CP};
 }

 # Calculate echo mass. If subwindow is saturated, echo_mass is extracted 
 # from the whole window (radar.subwindow_result.subwindow_id = 0).
  
 my $echo_mass;
 if($sub_window->{bird_echo_density} > 0) {
   $echo_mass = $sub_window->{bird_mass_density} / $sub_window->{bird_echo_density};
 } elsif($whole_window->{bird_echo_density} > 0) {
   $echo_mass = $whole_window->{bird_mass_density} / $whole_window->{bird_echo_density};
 } else {
   $echo_mass = 400;
 }

 # Calculate adjusted density (#/km²), quality parameter (0..1) and 
 # correction level for peak adjustments (1..3)
 if ($whole_window->{total_mass_density} < 10 and 
     $whole_window->{land_cl_perc} == 0 and 
     $whole_window->{n} == 0)  {
   # No data in image: total_mass<10, land_cl_perc=0, n=0
   $ROB_density = undef;
   $ROB_quality = 0;
 } elsif($sub_window->{rain_cl_perc} == 100 and $sub_window->{land_cl_perc} == 100) {
   $ROB_density = undef;
   $ROB_quality = 0;
 } elsif($correction_level > $cthresh) { # S/N ratio is above threshold, measurement removed
   $ROB_density = undef;
   $ROB_quality = 0;
 } elsif ($sub_window->{rain_cl_perc} > 90 and 
          ($sub_window->{rain_cl_perc}-$sub_window->{land_cl_perc}) >= $CP and $echo_mass > 0) {
   $ROB_density = ($sub_window->{total_mass_density} - $defReflectivity) / $echo_mass;
   $ROB_quality = sqrt( (100 - $sub_window->{land_cl_perc}) / (100 - $defClut) );
   $ROB_cor_level = 3;
 } elsif ($sub_window->{rain_cl_perc}-$sub_window->{land_cl_perc} >= ($ClutPerc - $defClut) * 1.5 and $echo_mass > 0) {
   $ROB_quality = (100 - $sub_window->{land_cl_perc}) / (100 - $defClut);
   $ROB_density = ($sub_window->{total_mass_density} - $sub_window->{land_mass_density}) / $echo_mass;
   if($ROB_quality > 0.8) {
     $ROB_cor_level = 1;
   } elsif($ROB_quality > 0.5) {
     $ROB_cor_level = 2;
   }
 } elsif ($sub_window->{bird_echo_density} > 0.05 and $echo_mass > 800) {
   $ROB_quality = sqrt((100 - $sub_window->{rain_cl_perc}) / (100 - $defClut));
   $ROB_density = ($sub_window->{total_mass_density} - $sub_window->{land_mass_density}) / $echo_mass;
   if($ROB_quality > 0.8) {
     $ROB_cor_level = 1;
   } elsif($ROB_quality > 0.5) {
     $ROB_cor_level = 2;
   }
 } else {
   $ROB_quality = sqrt((100 - $sub_window->{land_cl_perc}) / (100 - $defClut));
   $ROB_density = $sub_window->{bird_echo_density};
   if($ROB_quality > 0.8) {
     $ROB_cor_level = 1;
   } elsif($ROB_quality > 0.5) {
     $ROB_cor_level = 2;
   }
 }
 return ( $ROB_density, $ROB_quality, $ROB_cor_level);
 }