Mapping Hacks

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Chapter 5, Mapping with Gadgets

#61 Build a Map of Local GSM Cells

HACK

Also, you’ll need the Device::Modem module from the CPAN to run this

code. You can obtain it by running

perl -MCPAN -e 'install Device::Modem'

as root on your Linux system.

The Code

Here is the code contained in cellstumbler.pl:

#!/usr/bin/perl

use 5.6.1;

use IO::Socket;

use Device::Modem;

use Getopt::Std;

use strict;

use warnings;

BEGIN { $|++ }; # autoflush STDOUT.

# Read command line options.

my %opt;

getopt('gpr', \%opt);

# Set parameters based on command line options, with defaults.

my $GPSD = $opt{g} || "localhost:2947";

my $GSM_Port = $opt{p} || "/dev/ttyS0";

my $GSM_Baud = $opt{b} || 115_200;

my $Rate = $opt{r} || 1;

# Connect to gpsd.

my $gps = IO::Socket::INET->new($GPSD)

or die "Can't connect to gpsd at $GPSD: $!\n";

# Connect to the cell phone.

my $gsm = Device::Modem->new( port => $GSM_Port );

$gsm->connect( baudrate => $GSM_Baud )

or die "Can't connect to modem on $GSM_Port: $!\n";

# Tell the cell phone we want all the network registration data it has.

$gsm->reset;

$gsm->atsend( "AT+CREG=2\r" );

die "AT+CREG not recognized by modem on $GSM_Port"

unless $gsm->answer eq "OK";

while (1) {

# Tell gpsd we want position, date, and status.

$gps->print("pds\n");

# Parse out the response. If the date is blank, gpsd needs a second to

catch up.

my $location = <$gps>;

my ($lat, $long, $date, $status) =