bugfix: Fix computation of TOW value for GLONASS GNAV

Fixes the TOW computation mapping from GLONASS Time to UTC time and then
conversion to TOW and WN. The logic of the conversion considers time
offsets but  may need to be reviewed.

conf/gnss-sdr_GLONASS_L1_CA_ibyte.conf

@@ -5,7 +5,7 @@ GNSS-SDR.internal_fs_sps=6625000
 
 ;######### SIGNAL_SOURCE CONFIG ############
 SignalSource.implementation=File_Signal_Source
-SignalSource.filename=/archive/NT1065_GLONASS_L1_20160831_fs6625e6_if0e3_schar_1m.bin ; <- PUT YOUR FILE HERE
+SignalSource.filename=/archive/NT1065_GLONASS_L1_20160923_fs6625e6_if0e3_schar.bin ; <- PUT YOUR FILE HERE
 SignalSource.item_type=ibyte
 SignalSource.sampling_frequency=6625000
 ;SignalSource.freq=0
@@ -29,11 +29,11 @@ Channel.signal=1G
 Channels.in_acquisition=1
 Channels_1G.count=5
 
-Channel0.satellite=11
+Channel0.satellite=24   ; k=
-Channel1.satellite=2
+Channel1.satellite=1    ; k=1
-Channel2.satellite=18
+Channel2.satellite=2    ; k=-4
-Channel3.satellite=12
+Channel3.satellite=20   ; k=-5
-Channel4.satellite=21
+Channel4.satellite=21   ; k=4
 
 ;######### ACQUISITION GLOBAL CONFIG ############
 Acquisition_1G.implementation=GLONASS_L1_CA_PCPS_Acquisition

src/algorithms/PVT/gnuradio_blocks/rtklib_pvt_cc.cc

@@ -191,7 +191,8 @@ void rtklib_pvt_cc::msg_handler_telemetry(pmt::pmt_t msg)
                     // insert new ephemeris record
                     DLOG(INFO) << "GLONASS GNAV New Ephemeris record inserted in global map with TOW =" << glonass_gnav_eph->d_TOW
                                << ", GLONASS GNAV Week Number =" << glonass_gnav_eph->d_WN
-                               << " and Ephemeris IOD = " << glonass_gnav_eph->compute_GLONASS_time(glonass_gnav_eph->d_t_b);
+                               << " and Ephemeris IOD = " << glonass_gnav_eph->compute_GLONASS_time(glonass_gnav_eph->d_t_b)
+                               << " from SV = " << glonass_gnav_eph->i_satellite_slot_number;
                     // update/insert new ephemeris record to the global ephemeris map
                     d_ls_pvt->glonass_gnav_ephemeris_map[glonass_gnav_eph->i_satellite_PRN] = *glonass_gnav_eph;
                 }
@@ -209,7 +210,8 @@ void rtklib_pvt_cc::msg_handler_telemetry(pmt::pmt_t msg)
                     std::shared_ptr<Glonass_Gnav_Almanac> glonass_gnav_almanac;
                     glonass_gnav_almanac = boost::any_cast<std::shared_ptr<Glonass_Gnav_Almanac>>(pmt::any_ref(msg));
                     d_ls_pvt->glonass_gnav_almanac = *glonass_gnav_almanac;
-                    DLOG(INFO) << "New GLONASS GNAV Almanac has arrived ";
+                    DLOG(INFO) << "New GLONASS GNAV Almanac has arrived "
+                    << ", GLONASS GNAV Slot Number =" << glonass_gnav_almanac->d_n_A;
                 }
             else
                 {

src/core/receiver/gnss_flowgraph.cc

@@ -598,7 +598,7 @@ void GNSSFlowgraph::set_signals_list()
             29, 30, 31, 32, 33, 34, 35, 36};
 
     // Removing satellites sharing same frequency number(1 and 5, 2 and 6, 3 and 7, 4 and 6, 11 and 15, 12 and 16, 14 and 18, 17 and 21
-    std::set<unsigned int> available_glonass_prn = { 1, 2, 3, 4, 9, 10, 11, 12, 18, 19, 20, 21 };
+    std::set<unsigned int> available_glonass_prn = { 1, 2, 3, 4, 9, 10, 11, 12, 18, 19, 20, 21, 24 };
 
     std::string sv_list = configuration_->property("Galileo.prns", std::string("") );
 

src/core/system_parameters/GLONASS_L1_CA.h

@@ -87,6 +87,7 @@ const double GLONASS_L1_CA_CODE_LENGTH_CHIPS = 511.0;         //!< GLONASS L1 C/
 const double GLONASS_L1_CA_CODE_PERIOD       = 0.001;         //!< GLONASS L1 C/A code period [seconds]
 const double GLONASS_L1_CA_CHIP_PERIOD       = 1.9569e-06;    //!< GLONASS L1 C/A chip period [seconds]
 const double GLONASS_L1_CA_SYMBOL_RATE_BPS   = 1000;
+const int GLONASS_L1_CA_NBR_SATS             = 24; // STRING DATA WITHOUT PREAMBLE
 
 //FIXME Probably should use leap seconds definitions of rtklib
 const double GLONASS_LEAP_SECONDS[21][7] = { /* leap seconds (y,m,d,h,m,s,utc-gpst) */
@@ -135,7 +136,7 @@ const std::map<unsigned int, int> GLONASS_PRN =
                                                 {17, 4,},  //Plane 3
                                                 {18,-3,},  //Plane 3
                                                 {19, 3,},  //Plane 3
-                                                {20, 2,},  //Plane 3
+                                                {20, -5,},  //Plane 3
                                                 {21, 4,},  //Plane 3
                                                 {22,-3,},  //Plane 3
                                                 {23, 3,},  //Plane 3

src/core/system_parameters/glonass_gnav_navigation_message.cc

@@ -89,6 +89,11 @@ void Glonass_Gnav_Navigation_Message::reset()
     d_dtr = 0.0;
     d_satClkDrift = 0.0;
 
+    // Data update information
+    d_previous_tb = 0.0;
+    for(unsigned int i = 0; i < GLONASS_L1_CA_NBR_SATS; i++)
+        d_previous_Na[i] = 0.0;
+
 
     std::map<int,std::string> satelliteBlock; //!< Map that stores to which block the PRN belongs http://www.navcen.uscg.gov/?Do=constellationStatus
 
@@ -314,23 +319,74 @@ unsigned int Glonass_Gnav_Navigation_Message::get_frame_number(unsigned int sate
     return frame_ID;
 }
 
-
+double Glonass_Gnav_Navigation_Message::get_WN()
-double Glonass_Gnav_Navigation_Message::get_TOW()
 {
-    double TOW = 0.0;
+    double WN = 0.0;
-    double utcsu2utc = 3*3600;
+    double days = 0.0;
-    double glot2utcsu = 3*3600;
+    double total_sec = 0.0;
     int i = 0;
 
-    TOW = gnav_ephemeris.d_t_k + glot2utcsu + utcsu2utc + gnav_utc_model.d_tau_c + gnav_utc_model.d_tau_gps;
+    boost::gregorian::date gps_epoch { 1980, 1, 6 };
+    // Map to UTC
+    boost::gregorian::date glo_date(gnav_ephemeris.d_yr, 1, 1);
+    boost::gregorian::days d2(gnav_ephemeris.d_N_T);
+    glo_date = glo_date + d2;
+
+
+    boost::posix_time::time_duration t(-6, 0, 0);
+    boost::posix_time::ptime glo_time(glo_date, t);
+    boost::gregorian::date utc_date = glo_time.date();
+
+    days =  static_cast<double>((utc_date - gps_epoch).days());
+    total_sec = days*86400;
 
     for (i = 0; GLONASS_LEAP_SECONDS[i][0]>0; i++)
     {
         if (GLONASS_LEAP_SECONDS[i][0] == gnav_ephemeris.d_yr)
         {
-                TOW -= GLONASS_LEAP_SECONDS[i][6];
+            // We add the leap second when going from utc to gpst
+            total_sec += GLONASS_LEAP_SECONDS[i][6];
         }
     }
+
+
+    WN = floor(total_sec/604800);
+
+    return WN;
+}
+
+
+double Glonass_Gnav_Navigation_Message::get_TOW()
+{
+    double TOD = 0.0;
+    double TOW = 0.0;
+    double dayofweek = 0.0;
+    double utcsu2utc = 3*3600;
+    double glot2utcsu = 3*3600;
+    int i = 0;
+
+    // tk is relative to UTC(SU) + 3.00 hrs, so we need to convert to utc and add corrections
+    TOD = gnav_ephemeris.d_t_k - glot2utcsu - utcsu2utc + gnav_utc_model.d_tau_c + gnav_utc_model.d_tau_gps;
+
+
+    boost::gregorian::date glo_date(gnav_ephemeris.d_yr, 1, 1);
+    boost::gregorian::days d2(gnav_ephemeris.d_N_T);
+    glo_date = glo_date + d2;
+
+    dayofweek = static_cast<double>(glo_date.day_of_week());
+    TOW = TOD + dayofweek*86400;
+
+    for (i = 0; GLONASS_LEAP_SECONDS[i][0]>0; i++)
+        {
+            if (GLONASS_LEAP_SECONDS[i][0] == gnav_ephemeris.d_yr)
+            {
+                // We add the leap second when going from utc to gpst
+                TOW += GLONASS_LEAP_SECONDS[i][6];
+            }
+        }
+    // Compute the arithmetic modules to wrap around range
+    TOW = TOW - 604800*floor(TOW/604800);
+
     return TOW;
 }
 
@@ -342,13 +398,14 @@ int Glonass_Gnav_Navigation_Message::string_decoder(std::string frame_string)
     d_frame_ID = 0;
 
     // Unpack bytes to bits
-    std::bitset<GLONASS_GNAV_STRING_BITS> string_bits = std::bitset<GLONASS_GNAV_STRING_BITS>((frame_string));
+    std::bitset<GLONASS_GNAV_STRING_BITS> string_bits (frame_string);
 
     // Perform data verification and exit code if error in bit sequence
     flag_CRC_test = CRC_test(string_bits);
     if(flag_CRC_test == false)
         return 0;
 
+
     // Decode all 15 string messages
     d_string_ID = static_cast<unsigned int>(read_navigation_unsigned(string_bits, STRING_ID));
     switch (d_string_ID) {
@@ -461,6 +518,8 @@ int Glonass_Gnav_Navigation_Message::string_decoder(std::string frame_string)
                     if (flag_ephemeris_str_1 == true)
                     {
                         d_TOW = get_TOW();
+                        gnav_ephemeris.d_TOW = d_TOW;
+                        gnav_ephemeris.d_WN = get_WN();
                         flag_TOW_set = true;
                     }
 
@@ -730,20 +789,29 @@ Glonass_Gnav_Almanac Glonass_Gnav_Navigation_Message::get_almanac(unsigned int s
 
 bool Glonass_Gnav_Navigation_Message::have_new_ephemeris() //Check if we have a new ephemeris stored in the galileo navigation class
 {
+    bool new_eph = false;
     // We need to make sure we have received the ephemeris info plus the time info
     if ((flag_ephemeris_str_1 == true) and (flag_ephemeris_str_2 == true) and
         (flag_ephemeris_str_3 == true) and (flag_ephemeris_str_4 == true) and
         (flag_utc_model_str_5 == true))
+        {
+            if(d_previous_tb != gnav_ephemeris.d_t_b)
                 {
                     flag_ephemeris_str_1 = false;// clear the flag
                     flag_ephemeris_str_2 = false;// clear the flag
                     flag_ephemeris_str_3 = false;// clear the flag
                     flag_ephemeris_str_4 = false;// clear the flag
                     flag_all_ephemeris = true;
+                    // Update the time of ephemeris information
+                    d_previous_tb = gnav_ephemeris.d_t_b;
                     DLOG(INFO) << "GLONASS GNAV Ephemeris (1, 2, 3, 4) have been received and belong to the same batch" << std::endl;
+                    new_eph = true;
                 }
-    else
+
-        return false;
+        }
+
+
+    return new_eph;
 }
 
 
@@ -763,36 +831,52 @@ bool Glonass_Gnav_Navigation_Message::have_new_almanac() //Check if we have a ne
 {
     bool new_alm = false;
     if ((flag_almanac_str_6 == true) and (flag_almanac_str_7 == true))
+        {
+            if (d_previous_Na[i_alm_satellite_slot_number] != gnav_utc_model.d_N_A)
                 {
                     //All almanac have been received for this satellite
                     flag_almanac_str_6 = false;
                     flag_almanac_str_7 = false;
                     new_alm = true;
                 }
+
+        }
     if ((flag_almanac_str_8 == true) and (flag_almanac_str_9 == true))
+        {
+            if (d_previous_Na[i_alm_satellite_slot_number] != gnav_utc_model.d_N_A)
                 {
                     flag_almanac_str_8 = false;
                     flag_almanac_str_9 = false;
                     new_alm = true;
                 }
+        }
     if((flag_almanac_str_10 == true) and (flag_almanac_str_11 == true))
+        {
+            if (d_previous_Na[i_alm_satellite_slot_number] != gnav_utc_model.d_N_A)
                 {
                     flag_almanac_str_10 = false;
                     flag_almanac_str_11 = false;
                     new_alm = true;
                 }
+        }
     if((flag_almanac_str_12 == true) and (flag_almanac_str_13 == true))
+        {
+            if (d_previous_Na[i_alm_satellite_slot_number] != gnav_utc_model.d_N_A)
                 {
                     flag_almanac_str_12 = false;
                     flag_almanac_str_13 = false;
                     new_alm = true;
                 }
+        }
     if((flag_almanac_str_14 == true) and (flag_almanac_str_15 == true))
+        {
+            if (d_previous_Na[i_alm_satellite_slot_number] != gnav_utc_model.d_N_A)
                 {
                     flag_almanac_str_14 = false;
                     flag_almanac_str_15 = false;
                     new_alm = true;
                 }
+        }
 
     return new_alm;
 }

src/core/system_parameters/glonass_gnav_navigation_message.h

@@ -67,9 +67,9 @@ public:
 
     Glonass_Gnav_Ephemeris gnav_ephemeris;    //!< Ephemeris information decoded
     Glonass_Gnav_Utc_Model gnav_utc_model;    //!< UTC model information
-    Glonass_Gnav_Almanac gnav_almanac[24];    //!< Almanac information for all 24 satellites
+    Glonass_Gnav_Almanac gnav_almanac[GLONASS_L1_CA_NBR_SATS];    //!< Almanac information for all 24 satellites
 
-    //!< Ephmeris Flags
+    //!< Ephmeris Flags and control variables
     bool flag_all_ephemeris;      //!< Flag indicating that all strings containing ephemeris have been received
     bool flag_ephemeris_str_1;    //!< Flag indicating that ephemeris 1/4 (string 1) have been received
     bool flag_ephemeris_str_2;    //!< Flag indicating that ephemeris 2/4 (string 2) have been received
@@ -108,6 +108,10 @@ public:
     double d_dtr;            // Relativistic clock correction term
     double d_satClkDrift;    // Satellite clock drift
 
+    // Data update parameters
+    double d_previous_tb;
+    double d_previous_Na[GLONASS_L1_CA_NBR_SATS];
+
     bool CRC_test(std::bitset<GLONASS_GNAV_STRING_BITS> bits);
 
     unsigned int get_frame_number(unsigned int satellite_slot_number);
@@ -159,6 +163,8 @@ public:
     */
     double get_TOW();
 
+    double get_WN();
+
     /*!
      * \brief Computes the Coordinated Universal Time (UTC) and returns it in [s]
      */