skyplot improvements

Add new --format optional argument. Allowed options: pdf, eps, png, svg. Default: pdf
Add new --version / -v optional arguments, show program version and exit
Improve --help / -h message
Improve error handling
Generate PDF files with embedded fonts, ready for journal submission
Improve argument handling
Improve documentation
Add explicit z-order control for cleaner display of labels in multiconstellation files

utils/skyplot/README.md

@@ -16,18 +16,19 @@ showing satellite visibility over time.
 ## Features
 
 - Processes RINEX navigation files.
+- Calculates satellite positions using broadcast ephemeris.
+- Plots satellite tracks in azimuth-elevation coordinates.
+- Customizable observer location.
+- Color-codes satellites by constellation (GPS, Galileo, GLONASS, BeiDou).
+- Elevation mask set to 5°, configurable via the `--elev-mask` option.
+- Outputs high-quality image in PDF format. EPS, PNG, and SVG formats are also
+  available via the `--format` option.
+- Non-interactive mode for CI jobs with the `--no-show` option.
+- Constellations to plot can be configured via the `--system` option.
 - Optionally uses an OBS file to limit plot to the receiver observation time
   (`--use-obs`).
   - When enabled, the tool looks for a matching file by replacing the last
-    character of the NAV filename with O/o and uses it if found.
+    character of the NAV filename with `O`/`o` and uses it if found.
-- Calculates satellite positions using broadcast ephemeris.
-- Plots satellite tracks in azimuth-elevation coordinates.
-- Elevation mask set to 5°, configurable via the `--elev-mask` flag.
-- Color-codes satellites by constellation (GPS, Galileo, GLONASS, BeiDou).
-- Constellations to plot can be configured via the `--system` flag.
-- Customizable observer location.
-- Outputs high-quality image in PDF format.
-- Non-interactive mode for CI jobs (with `--no-show` flag).
 
 ## Requirements
 
@@ -41,21 +42,27 @@ showing satellite visibility over time.
 ### Basic Command
 
 ```
-./skyplot.py <RINEX_FILE> [LATITUDE] [LONGITUDE] [ALTITUDE] [--use-obs] [--elev-mask] [--system ...] [--no-show]
+./skyplot.py <RINEX_FILE> [LATITUDE] [LONGITUDE] [ALTITUDE]
+             [--elev-mask ELEV_MASK]
+             [--format {pdf,eps,png,svg}]
+             [--no-show]
+             [--system SYSTEM [SYSTEM ...]]
+             [--use-obs]
 ```
 
 ### Arguments
 
 | Argument         | Type     | Units       | Description              | Default  |
-| ---------------- | -------- | ----------- | ---------------------- | -------- |
+| ---------------- | -------- | ----------- | ------------------------ | -------- |
 | `RINEX_NAV_FILE` | Required | -           | RINEX nav file path      | -        |
 | `LATITUDE`       | Optional | degrees (°) | North/South position     | 41.275°N |
 | `LONGITUDE`      | Optional | degrees (°) | East/West position       | 1.9876°E |
 | `ALTITUDE`       | Optional | meters (m)  | Height above sea level   | 80.0 m   |
-| `--use-obs`      | Optional | -           | Use RINEX obs data     | -        |
 | `--elev-mask`    | Optional | degrees (°) | Elevation mask           | 5°       |
-| `--system`       | Optional | -           | Systems to plot        | All      |
+| `--format`       | Optional | -           | Output {pdf,eps,png,svg} | pdf      |
 | `--no-show`      | Optional | -           | Do not show plot         | -        |
+| `--system`       | Optional | -           | Systems to plot          | All      |
+| `--use-obs`      | Optional | -           | Use RINEX obs data       | -        |
 
 ### Examples
 
@@ -84,6 +91,10 @@ showing satellite visibility over time.
   ```
   ./skyplot.py brdc0010.22n -33.4592 -70.6453 520.0 --system G E
   ```
+- Get a PNG file:
+  ```
+  ./skyplot.py brdc0010.22n -33.4592 -70.6453 520.0 --format png
+  ```
 
 ## Output
 
@@ -91,8 +102,12 @@ The script generates a PDF file named `skyplot_<RINEX_FILE>.pdf` (with dots in
 `<RINEX_FILE>` replaced by `_`) with:
 
 - Satellite trajectories over all epochs in the file.
-  - NAV file - ephemeris time range (default)
+  - NAV file - ephemeris time range (default).
-  - Receiver observation if `--use-obs` is specified and OBS file is found
+  - Receiver observation if `--use-obs` is specified and OBS file is found.
 - Color-coded by constellation.
 - Observer location in title.
 - Time range in footer.
+- Embedded fonts that display consistently across all systems and generate
+  publication-ready figures.
+- EPS, PNG, and SVG output formats available via `--format eps`, `--format png`,
+  and `--format svg`.

utils/skyplot/skyplot.py

@@ -2,10 +2,17 @@
 """
  skyplot.py
 
- Reads a RINEX navigation file and generates a skyplot. Optionally, a RINEX observation file can 
+ Reads a RINEX navigation file and generates a skyplot. Optionally, a RINEX
- also be read to match the skyplot to the receiver processing time.
+ observation file can also be read to match the skyplot to the receiver
+ processing time.
 
- Usage: python skyplot.py <RINEX_NAV_FILE> [observer_lat] [observer_lon] [observer_alt] [--use-obs] 
+ Usage:
+    skyplot.py <RINEX_NAV_FILE> [observer_lat] [observer_lon] [observer_alt]
+                [--elev-mask ELEV_MASK]
+                [--format {pdf,eps,png,svg}]
+                [--no-show]
+                [--system SYSTEM [SYSTEM ...]]
+                [--use-obs]
 
  -----------------------------------------------------------------------------
 
@@ -25,9 +32,15 @@ from datetime import datetime, timedelta
 from math import atan2, cos, sin, sqrt
 from pathlib import Path
 
-import matplotlib.pyplot as plt
+try:
-import numpy as np
+    import matplotlib.pyplot as plt
+    import numpy as np
+except ImportError:
+    print("Error: This script requires matplotlib and numpy.")
+    print("Install them with: pip install matplotlib numpy")
+    sys.exit(1)
 
+__version__ = "1.0.0"
 
 def _read_obs_time_bounds(obs_path):
     """Return (start_time, end_time) from a RINEX 2/3 OBS file by scanning epoch lines.
@@ -360,9 +373,15 @@ def ecef_to_az_el(x, y, z, obs_lat, obs_lon, obs_alt):
 def plot_satellite_tracks(satellites, obs_lat, obs_lon, obs_alt,
                          footer_text=None, filename=None,
                          show_plot=True, start_time=None, 
-                         end_time=None, elev_mask=5.0):
+                         end_time=None, elev_mask=5.0,
+                         output_format="pdf"):
     """Plot trajectories for all visible satellites"""
-    plt.rcParams["font.family"] = "Times New Roman"
+    plt.rcParams['pdf.fonttype'] = 42  # TrueType fonts
+    plt.rcParams['ps.fonttype'] = 42   # TrueType fonts
+    plt.rcParams['font.family'] = 'serif'
+    plt.rcParams['font.serif'] = ['Times New Roman', 'Times', 'DejaVu Serif']
+    plt.rcParams['mathtext.fontset'] = 'dejavuserif'  # For math text
+    plt.rcParams['svg.fonttype'] = 'none'             # Make SVG text editable
     fig = plt.figure(figsize=(8, 8))
     ax = fig.add_subplot(111, projection='polar')
     ax.tick_params(labelsize=16, pad=7)
@@ -442,13 +461,13 @@ def plot_satellite_tracks(satellites, obs_lat, obs_lon, obs_alt,
         for az_seg, el_seg in segments:
             theta = np.radians(az_seg)
             r = 90 - np.array(el_seg)
-            ax.plot(theta, r, '-', color=color, alpha=0.7, linewidth=2.5)
+            ax.plot(theta, r, '-', color=color, alpha=0.7, linewidth=2.5, zorder=1)
 
             # Arrow at end
             if len(theta) >= 2:
                 dx = theta[-1] - theta[-2]
                 dy = r[-1] - r[-2]
-                arrow_length_factor = 1.3
+                arrow_length_factor = 1.8
                 extended_theta = theta[-2] + dx * arrow_length_factor
                 extended_r = r[-2] + dy * arrow_length_factor
                 ax.annotate('',
@@ -461,13 +480,15 @@ def plot_satellite_tracks(satellites, obs_lat, obs_lon, obs_alt,
                                 'linewidth': 1.5,
                                 'shrinkA': 0,
                                 'shrinkB': 0
-                            })
+                            },
+                            zorder=2)
 
             # Label at midpoint of the segment
             mid_idx = len(theta)//2
             ax.text(theta[mid_idx], r[mid_idx], prn,
                     fontsize=12, ha='center', va='center',
-                    bbox={"facecolor": "white", "alpha": 0.8, "pad": 2})
+                    bbox={"facecolor": "white", "alpha": 0.8, "pad": 2},
+                    zorder=3)
 
     # Legend for present systems
     legend_elements = [
@@ -503,11 +524,11 @@ def plot_satellite_tracks(satellites, obs_lat, obs_lon, obs_alt,
     if filename:
         filename_no_path = Path(filename).name
         filename_no_dots = filename_no_path.replace('.', '_')
-        output_name = f"skyplot_{filename_no_dots}.pdf"
+        output_name = f"skyplot_{filename_no_dots}.{output_format}"
     else:
-        output_name = "skyplot.pdf"
+        output_name = f"skyplot.{output_format}"
 
-    plt.savefig(output_name, format='pdf', bbox_inches='tight')
+    plt.savefig(output_name, format=output_format, bbox_inches='tight')
     print(f"Image saved as {output_name}")
     if show_plot:
         plt.show()
@@ -517,6 +538,7 @@ def plot_satellite_tracks(satellites, obs_lat, obs_lon, obs_alt,
 
 def main():
     """Generate the skyplot"""
+    try:
         # Set system names and codes
         system_name_to_code = {
             'GPS': 'G',
@@ -530,66 +552,80 @@ def main():
 
         # Set up argument parser
         parser = argparse.ArgumentParser(
-        description='Generate GNSS skyplot from RINEX navigation file',
+            description='Generate a GNSS skyplot from a RINEX navigation file',
-        add_help=False
+            epilog="Example: skyplot.py brdc0010.22n -33.4592 -70.6453 520.0 --format png --system G E --elev-mask 10 --no-show"
+        )
+
+        # Positional arguments
+        parser.add_argument(
+            'filename',
+            help='RINEX navigation file path'
+        )
+
+        parser.add_argument(
+            'lat', nargs='?', type=float, default=41.2750,
+            help='Observer latitude in degrees (default: 41.275° N)'
+        )
+
+        parser.add_argument(
+            'lon', nargs='?', type=float, default=1.9876,
+            help='Observer longitude in degrees (default: 1.9876° E)'
+        )
+
+        parser.add_argument(
+            'alt', nargs='?', type=float, default=80.0,
+            help='Observer altitude in meters (default: 80.0 m)'
+        )
+
+        # Optional arguments
+        parser.add_argument(
+            '--elev-mask',
+            type=float,
+            default=5.0,
+            help='Elevation mask in degrees for plotting satellite tracks (default: 5°)'
+        )
+
+        parser.add_argument(
+            '--format',
+            type=str,
+            default="pdf",
+            choices=["pdf", "eps", "png", "svg"],
+            help='Output file format for plot (default: pdf)'
         )
 
-    # Add the no-show flag
         parser.add_argument(
             '--no-show',
             action='store_true',
             help='Run without displaying plot window'
         )
-    # Add the use-obs flag
+
+        parser.add_argument(
+            '--system',
+            nargs='+',
+            help='Only plot satellites from these systems (e.g., G R E or GPS GLONASS Galileo)'
+        )
+
         parser.add_argument(
             '--use-obs',
             action='store_true',
             help='Use corresponding RINEX observation file to bound the skyplot to the receiver time window'
         )
-    # Add the elev-mask flag.
+
         parser.add_argument(
-        '--elev-mask', type=float, default=5.0,
+            "-v", "--version",
-        help='Elevation mask in degrees for plotting satellite tracks (default: 5°)'
+            action="version",
+            version=f"%(prog)s {__version__}",
+            help="Show program version and exit"
         )
-    # Add the system flag.
-    parser.add_argument(
-        '--system',
-        nargs='+',
-        help='Only plot satellites from these systems (e.g., G R E or GPS Galileo GLONASS)'
-    )
-    # Parse known args (this ignores other positional args)
-    args, remaining_args = parser.parse_known_args()
 
-    # Handle help manually
+        # Parse all arguments with full validation
-    if '-h' in remaining_args or '--help' in remaining_args:
+        args = parser.parse_args()
-        print("""
-Usage: python skyplot.py <RINEX_FILE> [LATITUDE] [LONGITUDE] [ALTITUDE] [--use-obs] [--elev-mask] [--system ...] [--no-show]
 
-Example:
+        # Convert coordinates to radians
-  python skyplot.py brdc0010.22n 41.275 1.9876 80.0 --use-obs --no-show --elev-mask=10 --system GPS Galileo
+        obs_lat = np.radians(args.lat)
-""")
+        obs_lon = np.radians(args.lon)
-        sys.exit(0)
+        obs_alt = args.alt
-
+        filename = args.filename
-    if len(remaining_args) < 1:
-        print("Error: RINEX file required")
-        sys.exit(1)
-
-    filename = remaining_args[0]
-
-    # Default observer location (Castelldefels, Barcelona, Spain)
-    obs_lat = np.radians(41.2750)
-    obs_lon = np.radians(1.9876)
-    obs_alt = 80.0
-
-    # Override with command line arguments if provided
-    if len(remaining_args) >= 4:
-        try:
-            obs_lat = np.radians(float(remaining_args[1]))
-            obs_lon = np.radians(float(remaining_args[2]))
-            if len(remaining_args) >= 5:
-                obs_alt = float(remaining_args[3])
-        except ValueError:
-            print("Invalid observer coordinates. Using defaults.")
 
         # Read RINEX file
         print(f"Reading {filename}...")
@@ -597,11 +633,11 @@ Example:
             satellites = read_rinex_nav(filename)
         except FileNotFoundError:
             print(f"Error: File '{filename}' not found.")
-        return
+            return 1
 
         if not satellites:
             print("No satellite data found in the file.")
-        return
+            return 1
 
         if args.system:
             systems_upper = set()
@@ -616,7 +652,7 @@ Example:
 
             if not satellites:
                 print(f"No satellites found for systems: {', '.join(sorted(systems_upper))}")
-            return
+                return 1
 
         # Print summary information
         all_epochs = sorted(list(set(
@@ -686,8 +722,14 @@ Example:
             show_plot=not args.no_show,
             start_time=use_start,
             end_time=use_end,
-        elev_mask=args.elev_mask
+            elev_mask=args.elev_mask,
+            output_format=args.format
         )
+    except Exception as e:
+        print(f"Error: {str(e)}")
+        return 1
+
+    return 0
 
 
 if __name__ == "__main__":