RINEX (Receiver Independent Exchange Format) is the standardized ASCII format for storing and exchanging raw GNSS observation and navigation data, enabling interoperability between receivers, processing software, and data archives from different manufacturers. Developed to facilitate international GNSS campaigns in the 1980s and continuously evolved since, RINEX has become the universal format for post-processed GNSS applications including surveying, geodesy, and scientific research.

RINEX files are organized into three main categories. Observation files contain the raw measurements collected by receivers: pseudoranges, carrier phases, Doppler shifts, and signal strength values for each tracked satellite at each epoch. Navigation files contain satellite ephemeris and clock data, the orbital parameters receivers need to compute satellite positions. Meteorological files capture temperature, pressure, and humidity observations used for tropospheric modeling. Each file begins with a header section containing metadata about the station, receiver, antenna, and data content, followed by the measurement data organized by epoch.

The RINEX format has evolved through multiple versions to accommodate modernizing GNSS capabilities. RINEX 2.x versions support GPS and GLONASS with limited signal distinction. RINEX 3.x versions introduced comprehensive multi-constellation support (GPS, GLONASS, Galileo, BeiDou, QZSS, SBAS) with explicit observation codes identifying each signal type. RINEX 4.x further refined multi-constellation handling and added support for emerging signals. Users must ensure format version compatibility between data and processing software.

For GNSS professionals, RINEX provides essential workflow capabilities. Data from any receiver can be processed in any software that supports RINEX, eliminating vendor lock-in. Reference station data from CORS networks is typically distributed in RINEX format, enabling post-processed positioning. Long-term data archives use RINEX (often with Hatanaka compression) for efficient storage and retrieval. Quality control tools analyze RINEX files to assess receiver performance and identify data issues. RINEX is the lingua franca of the precision GNSS community.