Module: PWN::SDR::Decoder::GPS

Defined in:
lib/pwn/sdr/decoder/gps.rb

Overview

GNSS / GPS L1-C/A (1575.42 MHz) & L2C (1227.60 MHz) decoder. BPSK/DSSS at 1.023 / 10.23 Mcps needs raw I/Q, so this drives gnss-sdr (or rtl_gps) directly and structures the PVT / NMEA lines it emits (satellite PRNs acquired, C/N0, computed position fix, UTC time).

Class Method Summary collapse

Class Method Details

.authors ⇒ Object

Author(s)

0day Inc. support@0dayinc.com



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# File 'lib/pwn/sdr/decoder/gps.rb', line 60

public_class_method def self.authors
  "AUTHOR(S):\n  0day Inc. <support@0dayinc.com>\n"
end

.decode(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::GPS.decode( freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq' )



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# File 'lib/pwn/sdr/decoder/gps.rb', line 18

public_class_method def self.decode(opts = {})
  freq_obj = opts[:freq_obj]
  raise 'ERROR: :freq_obj is required' unless freq_obj.is_a?(Hash)

  conf = (freq_obj[:gnss_conf] || '/usr/share/gnss-sdr/conf/gnss-sdr_GPS_L1_rtlsdr_realtime.conf').to_s
  direct_cmd = "gnss-sdr --config_file=#{Shellwords.escape(conf)}"

  PWN::SDR::Decoder::Base.run_pipeline(
    freq_obj: freq_obj,
    protocol: 'GPS',
    required_bins: %w[gnss-sdr],
    direct_cmd: direct_cmd,
    line_match: /(PVT|Position|PRN|Tracking|\$G[PN])/,
    parser: proc { |line| parse_line(line: line) }
  )
end

.help ⇒ Object

Display Usage for this Module



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# File 'lib/pwn/sdr/decoder/gps.rb', line 66

public_class_method def self.help
  puts "USAGE:
    #{self}.decode(
      freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq'
    )

    NOTE: Requires `gnss-sdr` and an active-antenna-biased front end.
          Override the receiver config via freq_obj[:gnss_conf].

    #{self}.parse_line(line: 'Position ... Lat = 32.7 Long = -97.1 Height = 210')

    #{self}.authors
  "
end

.parse_line(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::GPS.parse_line(line: 'Position at ... Lat = 32.7 [deg], Long = -97.1 ...')



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# File 'lib/pwn/sdr/decoder/gps.rb', line 38

public_class_method def self.parse_line(opts = {})
  line = opts[:line].to_s
  out  = { protocol: 'GPS' }
  out[:prn]  = ::Regexp.last_match(1) if line =~ /PRN[ =]?(\d{1,2})/
  out[:cn0]  = ::Regexp.last_match(1) if line =~ /CN0[ =]?([\d.]+)/i
  out[:lat]  = ::Regexp.last_match(1) if line =~ /Lat(?:itude)?\s*=\s*(-?[\d.]+)/i
  out[:lon]  = ::Regexp.last_match(1) if line =~ /Long(?:itude)?\s*=\s*(-?[\d.]+)/i
  out[:alt]  = ::Regexp.last_match(1) if line =~ /Height\s*=\s*(-?[\d.]+)/i
  out[:utc]  = ::Regexp.last_match(1) if line =~ /UTC\s*=?\s*([\d:.-]+T?[\d:.]*)/
  out[:nmea] = line if line.start_with?('$G')
  out[:summary] = if out[:lat]
                    "GPS FIX #{out[:lat]},#{out[:lon]} alt=#{out[:alt]}m"
                  elsif out[:prn]
                    "GPS PRN#{out[:prn]} CN0=#{out[:cn0]}"
                  else
                    "GPS #{line[0, 100]}"
                  end
  out.compact
end