cddis-highrate-downloader: CDDIS High-Rate GNSS Data Downloader

A Python-based tool to easily bulk-download high-rate GNSS data from NASA's CDDIS archive. This tool supports downloading, extracting, and converting GNSS data files with various filtering options.

Features

• Download high-rate GNSS data from CDDIS FTP server
• Support for station-specific downloads
• Date range support (DOY - Day of Year)
• Hour range filtering
• Automatic file extraction (.gz)
• Optional RINEX conversion (CRX to RNX)
• Anonymous FTP access (no credentials needed)
• Smart file handling (skips already downloaded/converted files)
• Robust connection handling with automatic retry mechanism
• Progress tracking and detailed error reporting

Prerequisites

• Python 3.6 or higher
• CRX2RNX executable (included for Windows, required for RINEX conversion)

Installation

1. Clone the repository:

git clone https://github.com/cemalialtuntas/cddis-highrate-downloader.git
cd cddis-highrate-downloader

2. Create and activate a virtual environment (recommended): Windows

python -m venv venv
venv\Scripts\activate

Linux/Mac

python -m venv venv
source venv/bin/activate

3. Install the package:

pip install -e .

Usage

After installation, you can run the tool using the command:

cddis-download

The tool will prompt you for the following information:

1. Station Name:

   • Enter a specific station code (e.g., "BRST00FRA")
   • Or press Enter for all stations

2. Year:

   • Enter the year (e.g., "2024")

3. DOY (Day of Year):

   • Enter a single day (e.g., "300")
   • Or enter a range (e.g., "300-305")

4. Subfolder:

   • Enter the subfolder name (e.g., "24d" or "24o")

5. Hour:

   • Enter a specific hour (e.g., "00")
   • Enter a range (e.g., "00-05")
   • Or press Enter for all hours

6. File Processing Options:

   • Extract downloaded files (y/N)
   • Convert to RINEX format (y/N)

Example Usage

$ cddis-download
Enter station name (e.g., BRST00FRA) or press Enter for ALL: BRST00FRA
Enter year (e.g., 2024): 2024
Enter DOY (e.g., 300 or 300-305): 300-302
Enter subfolder (e.g., 24d, 24o): 24d
Enter hour (e.g., 00 or 00-05) or press Enter for ALL: 00-03
Extract downloaded files? (y/N): y
Convert to RINEX (.rnx)? (y/N): y

Output Structure

Downloaded and processed files are organized in the following structure:

downloads/
└── [STATION_NAME]/
    └── [YEAR]/
        └── [DOY]/
            └── [HOUR]/
                ├── original.crx.gz  # If not extracted
                ├── original.crx     # If extracted
                └── original.rnx     # If converted to RINEX

File Formats

• .gz: Compressed files from CDDIS
• .crx: Hatanaka-compressed RINEX files
• .rnx: RINEX observation files (after conversion)

RINEX Conversion

The tool includes CRX2RNX.exe for Windows users. For other operating systems, ensure you have CRX2RNX installed and accessible in your system PATH.

Smart File Handling

The tool now includes intelligent file handling features:

• Skips downloading if RINEX (.rnx) file already exists
• Skips downloading if CRX file already exists
• Automatically retries failed downloads
• Resumes interrupted downloads from the last successful point

Connection Handling

Version 1.0.1 includes improved connection handling:

• Automatic reconnection on connection loss
• Multiple retry attempts with increasing delays
• Timeout settings to prevent hanging connections
• Passive mode support for better compatibility
• Detailed connection status reporting

Common Issues

1. FTP Connection Issues:

   • Ensure you have internet connectivity
   • Check if CDDIS server is accessible
   • The tool will automatically retry on connection failures

2. RINEX Conversion Errors:

   • Verify CRX2RNX is properly installed
   • Check file permissions

3. Invalid Input Formats:

   • DOY must be between 001-366
   • Hours must be between 00-23
   • Use correct station name format

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Author

Cemali Altuntas ([email protected])

Acknowledgments

• NASA's CDDIS for providing GNSS data
• RNXCMP for the CRX2RNX tool (Reference: Hatanaka, Y. (2008), A Compression Format and Tools for GNSS Observation Data, Bulletin of the Geospatioal Information Authority of Japan, 55, 21-30. available at https://www.gsi.go.jp/ENGLISH/Bulletin55.html)

Citation

If you use this tool in your research, please cite:

@software{cddis_highrate_downloader,
    author = {Altuntas, Cemali},
    title = {CDDIS High-Rate GNSS Data Downloader},
    version = {1.0.1},
    year = {2025},
    url = {https://github.com/cemalialtuntas/cddis-highrate-downloader}
}