my %HoH;
while (my $row = $csv->getline_hr($data)) {
    my $key = "$row->{latitude}.$row->{longitude}";
    # Compare
    next if exists $HoH{$key} && $row->{id} <= $HoH{$key}->{id};
    # Set (or overwrite)
    $HoH{$key} = {
        name => $row->{name},
        id   => $row->{id}
    };
}
# At this point I would return the hash (or a reference to it) but you would need to change the calling line, of course