Bushnell Backtrack D-Tour

[GPSVisualizer]

Here's an abridged/simplified version of GPS Visualizer's perl code anyway, in case it's useful for someone:

Code:

open(BTK,$file_path);
seek(BTK,24,0); # skip mysterious file header
while (!eof(BTK)) {
    read(BTK,my $type,1); $type = unpack("C",$type);
    if ($type == 3) { # track header
        read(BTK,my $trk_info,8); my ($unknown,$y,$mo,$d,$h,$m,$s) = unpack("c SCC CCC",$trk_info);
        seek(BTK,15,1);
        
        # [do something here with the time info from the header and start a new track]
        
    } else { # type 4 = end of track; type 2 = normal point
        read(BTK,my $temp,1); $temp = unpack("c",$temp)/2 + 20;
        read(BTK,my $number,2); $number = unpack("S",$number);
        read(BTK,my $alt,4); $alt = unpack("l",$alt)/10;
        read(BTK,my $lat,8); $lat = unpack("d",$lat);
        read(BTK,my $lon,8); $lon = unpack("d",$lon);
        
        # [do something here with the point data]
        
    }
}
close(BTK);