Mapping Hacks

Build a Map of Local GSM Cells #61

Chapter 5, Mapping with Gadgets

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275

HACK

($location =~ /P=(.+?) (.+?),D=(.+?),S=(.+?)/gos);

next unless $date;

# Turn the date into an RFC 2445 ICal date string.

my ($mo, $d, $y, $h, $m, $s) = split /[ \/:]/o, $date;

$date = "${y}${mo}${d}T${h}${m}${s}Z";

# Query cell ID and location area code.

$gsm->atsend( "AT+CREG?\r" );

my ($cid, $lac) = ($gsm->answer =~ /"([\dA-F]{4})"/gios);

# Query signal strength.

$gsm->atsend( "AT+CSQ\r" );

my ($signal) = ($gsm->answer =~ /(\d+)/gos);

$signal = -113 + $signal * 2;

# Print a line of data and wait.

print join(",", $date, $status, $lat, $long,

hex($cid), hex($lac), $signal), "\n";

sleep( $Rate );

}

Running the Code

As mentioned earlier, you need to have gpsd running before starting cell-

stumbler.pl. We used a Bluetooth RFCOMM serial connection to talk to a

Nokia 3650, so we had to bind an RFCOMM port first, using the six-part

Bluetooth ID of the phone. You can use

hcitool scan in Linux to search for

the Bluetooth ID of your phone. If your phone doesn’t have Bluetooth, then

you’ll need a serial cable, but you can skip the whole RFCOMM bit. You

may need to use a terminal program like minicom to poke around your sys-

tem’s serial ports to figure out which the phone is accessible on. You’ll

know it’s working when you type

AT<enter> into the terminal program, and

get an

OK from the phone in response.

Finally, assuming cellstumbler.pl ...