Skyplot: fix reading and handling of GLONASS ephemeris

utils/skyplot/skyplot.py

@@ -56,10 +56,12 @@ def parse_rinex_float(s):
 def read_rinex_nav(filename):
     """Read RINEX v3.0 navigation file"""
     satellites = {}
+    line_number = 0
     with open(filename, 'r', encoding='utf-8') as f:
         # Skip header
         while True:
             line = f.readline()
+            line_number += 1
             if not line:
                 return satellites  # Empty file
             if "END OF HEADER" in line:
@@ -67,15 +69,18 @@ def read_rinex_nav(filename):
 
         # Read ephemeris data
         current_line = f.readline()
+        line_number += 1
         while current_line:
             if len(current_line) < 23:
                 current_line = f.readline()
+                line_number += 1
                 continue
 
             prn = current_line[:3].strip()
+            system = prn[0]  # G, R, E, etc.
 
             try:
-                # Parse epoch fields with careful position handling
+                # Parse epoch fields
                 year = int(current_line[4:8])
                 month = int(current_line[9:11])
                 day = int(current_line[12:14])
@@ -86,19 +91,43 @@ def read_rinex_nav(filename):
                 year += 2000 if year < 80 else 0
                 epoch = datetime(year, month, day, hour, minute, second)
 
-                # Read the next 7 lines
+                # Read the next lines
                 lines = [current_line]
-                for _ in range(7):
+                line_count = 4 if system == 'R' else 7
+                for _ in range(line_count):
                     next_line = f.readline()
+                    line_number += 1
                     if not next_line:
                         break
                     lines.append(next_line)
 
-                if len(lines) < 8:
+                if len(lines) < line_count + 1:
                     current_line = f.readline()
+                    line_number += 1
                     continue
 
-                # Parse all ephemeris parameters with robust float handling
+                if system == 'R':  # GLONASS specific parsing
+                    ephemeris = {
+                        'prn': prn,
+                        'epoch': epoch,
+                        'sv_clock_bias': parse_rinex_float(lines[0][23:42]),
+                        'sv_relative_freq_bias': parse_rinex_float(lines[0][42:61]),
+                        'message_frame_time': parse_rinex_float(lines[0][61:80]),
+                        'x': parse_rinex_float(lines[1][4:23]),  # Position (km)
+                        'x_vel': parse_rinex_float(lines[1][23:42]),  # Velocity (km/s)
+                        'x_acc': parse_rinex_float(lines[1][42:61]),
+                        'health': parse_rinex_float(lines[1][61:80]),
+                        'y': parse_rinex_float(lines[2][4:23]),
+                        'y_vel': parse_rinex_float(lines[2][23:42]),
+                        'y_acc': parse_rinex_float(lines[2][42:61]),
+                        'freq_num': parse_rinex_float(lines[2][61:80]),
+                        'z': parse_rinex_float(lines[3][4:23]),
+                        'z_vel': parse_rinex_float(lines[3][23:42]),
+                        'z_acc': parse_rinex_float(lines[3][42:61]),
+                        'age': parse_rinex_float(lines[3][61:80])
+                    }
+                else:
+                    # Parse all ephemeris parameters
                     ephemeris = {
                         'prn': prn,
                         'epoch': epoch,
@@ -139,19 +168,35 @@ def read_rinex_nav(filename):
                 satellites[prn].append(ephemeris)
 
             except (ValueError, IndexError) as e:
-                print(f"Error parsing PRN {prn} at {epoch}: {e}")
+                print(f"\nError in file {filename} at line {line_number}:")
+                print(f"  PRN: {prn}")
+                print(f"  Line content: {current_line.strip()}")
+                print(f"  Error type: {type(e).__name__}")
+                print(f"  Error details: {str(e)}")
+                print("Skipping to next satellite block...\n")
                 # Skip to next block by reading until next PRN
                 while current_line and not current_line.startswith(prn[0]):
                     current_line = f.readline()
+                    line_number += 1
                 continue
 
             current_line = f.readline()
+            line_number += 1
 
     return satellites
 
 
 def calculate_satellite_position(ephemeris, transmit_time):
     """Calculate satellite position in ECEF coordinates at given transmission time"""
+    system = ephemeris['prn'][0]
+
+    if system == 'R':  # GLONASS - use position + velocity * time
+        dt = transmit_time
+        # Convert km to meters and add velocity component
+        xk = ephemeris['x'] * 1000 + ephemeris['x_vel'] * 1000 * dt
+        yk = ephemeris['y'] * 1000 + ephemeris['y_vel'] * 1000 * dt
+        zk = ephemeris['z'] * 1000 + ephemeris['z_vel'] * 1000 * dt
+    else:
         # Constants
         mu = 3.986005e14  # Earth's gravitational constant (m^3/s^2)
         omega_e_dot = 7.2921151467e-5  # Earth rotation rate (rad/s)
@@ -222,8 +267,7 @@ def calculate_satellite_positions(ephemeris, start_time, end_time, step_min=15):
     while current_time <= end_time:
         transmit_time = (current_time - ephemeris['epoch']).total_seconds()
 
-        # Only calculate positions within ephemeris validity (typically 4 hours)
-        if abs(transmit_time) <= 4 * 3600:
+        if abs(transmit_time) <= 14400:  # 4 hours
             x, y, z = calculate_satellite_position(ephemeris, transmit_time)
             positions.append((current_time, x, y, z))