RINEX: The Universal Language of GNSS Data

RINEX (Receiver Independent Exchange Format) is a standardized data format in the GNSS field, designed to unify observation data from receivers of different brands. Jointly developed by international organizations, it supports global satellite systems such as GPS, GLONASS, and BDS, and is compatible with nearly all survey-grade devices and analysis software.

In this article, we will provide a comprehensive overview of this essential format—from its definition, file naming conventions, and file structure to real-world applications. Through illustrations and examples, we will also break down the core logic behind RINEX.

1. Types of RINEX Files

The commonly used RINEX files are mainly divided into the following types:

1.1 Observation File

Usually with the extension “.o” or “.obs”, the observation file contains GNSS measurement data recorded by the receiver, such as pseudorange, carrier phase, and signal-to-noise ratio. These data are captured at the moment the satellite signals are measured by the receiver and serve as the foundation for high-precision positioning and data analysis.

1.2 Navigation File

Usually with the extension “.n” or “.nav”, the navigation file contains satellite navigation information, such as ephemeris data and clock offsets. This information is essential for calculating the satellites' positions and timing, and is crucial for positioning solutions.

1.3 Meteorological File

Usually with the extension “.m” or “.met”, the meteorological file contains weather data collected near the observation site, such as temperature, humidity, and atmospheric pressure. These data can be used to correct atmospheric errors and improve positioning accuracy.

2. Naming Conventions of RINEX Files

RINEX files follow strict naming conventions that convey information about the file’s origin, type, and the time period of the recorded data. The naming rules vary slightly between different RINEX versions, which will be explained separately below.

2.1 RINEX 2.x Version

The file name format is ssssdddf.yyt, where:

ssss: A 4-character station code;

ddd: The day of the year (DOY) corresponding to the first record in the file (i.e., the number of days since January 1st of that year);

f: The file sequence number within the day, ranging from 0 to 9 or A to Z. When it is 0, the file contains all data for the entire day;

yy: The last two digits of the year;

t: The file type, commonly including O (Observation file), N (GPS Navigation message file), M (Meteorological data file), G (GLONASS Navigation message file), etc.

For example, the file named hksc137a.21o represents an observation file for the Hong Kong station “hksc,” containing data from the first segment on the 137th day of 2021.

2.2 RINEX 3.x Version

The new RINEX format abandons the previous practice of including the observation year in the file extension and only uses two extensions: .rnx for standard RINEX files and .crx for compressed Compact RINEX files.

The file name format is:
<SITE><RN><CRC>_<S>_<YEARDOYHRMN>_<LEN>_<FRQ>_<ST>.<FMT>, where:

<SITE>: Four-character observation station name;

<RN>: Receiver number;

<CRC>: Three-character ISO 3166-1 country or region code, indicating the station location;

<S>: Data source, either from receiver (R) or data stream (S);

<YEARDOYHRMN>: Observation start time in the format Year, Day of Year, Hour, Minute;

<LEN>: Duration of the observation period;

<FRQ>: Sampling interval or frequency during observation (not included in navigation files);

<ST>: Satellite system and data type, where the first character indicates the satellite system (M, G, R, C, E, J, I), and the second character  indicates the data type: Observation file (O), Navigation file (N), or Meteorological file (M);

<FMT>: File extension, either rnx or crx.

For example, ALGO00CAN_R_20170420000_01D_30S_MO.rnx represents multi-system mixed observation data from receiver number 0 at the ALGO station in Canada, starting at midnight on the 42nd day of 2017, with a duration of 1 day and a sampling interval of 30 seconds.

3. Data Format of RINEX Files

RINEX files use text files (ASCII format) to store data, and the data record format is independent of the receiver manufacturer and specific model. Each RINEX file consists of two parts: the Header and the Data Records.

3.1 Observation Data File

The header of the file is located at the beginning and contains global information about the entire file, such as the RINEX version, file type, station information, receiver details, antenna information, observation time, and more. Each line in the header has a header label, located in columns 61-80 of the line, which indicates the content of that line. The header ends with the label "END OF HEADER," after which the data records begin.

Below is an example of the header of an RINEX 3.05 observation data file:

Figure 1. Example of Observation File Header and Explanation of Key Fields

In this example, the first line indicates that the RINEX version is 3.05, and the file type is an observation data file, meaning the observation data may contain different types of observations. The following lines are optional header lines that can include additional information about the observation station, measurement instruments, etc. The left side of each line contains specific information, while the right side provides a description of that information. The last line, "END OF HEADER," marks the end of the header.

The data records section immediately follows the header, and the content and format of the data stored vary depending on the file type.

Observation data files store data records in chronological order, typically segmented by seconds. Each time point records the observation data of the satellite signals at that moment, including pseudorange, carrier phase, Doppler shift, and signal quality. Below is an example of data records in an observation data file:

Figure 2. Example of Observation File Data Section and Explanation of Key Fields

In this example, there are observation data for two time points. The first line contains information such as the observation epoch time, epoch flag, and the total number of satellites. The following lines record the observation data for each satellite (such as G06, E11, etc.) at that specific moment. Each satellite’s observation data includes multiple values, such as pseudorange, carrier phase, etc. The specific types of information included can be found in the OBS TYPE section of the header.

3.2 Navigation File

The data records in a navigation file mainly contain satellite clock correction model parameters and satellite orbit data. Below is an example of a RINEX navigation file, which will allow us to more intuitively understand its content structure. 

Figure 3. Example of Navigation File and Explanation of Key Fields

The header of the navigation file mainly contains information such as the file type, ionospheric correction parameters, time system parameters, and leap seconds. The data section includes information such as TOC (Epoch of the clock), satellite clock bias, and satellite clock drift.

For more detailed information, you can refer to the IGS official documentation on RINEX files.

4. How to Obtain and Process RINEX Files Using SinoGNSS Products

4.1 Obtaining RINEX Files

Please refer to the blog "Logging Raw Observation Data for GNSS Devices" for storing GNSS raw data using the K8 Series GNSS Boards.

4.2 RINEX File Format Conversion

Please refer to the blog ‘A Quick Method for Calculating Precise Coordinates (1 cm Accuracy) Anywhere in the World’ for converting raw data to RINEX format using CRU software.

4.3 RINEX File Data Analysis

RINEX files can be processed and analyzed using professional software or programming tools. Popular software includes RTKLIBand TEQC. Our company’s proprietary software, Compass Solution, also provides data processing and analysis for RINEX files:

• Data Integrity: Checks whether the observation period is continuous and if there are any data interruptions.
• Multipath Effects: Analyzes Signal-to-Noise Ratio (SNR) and residuals to assess multipath errors.
• Cycle Slip Detection: Detects if there are any cycle slips in carrier phase observations.
• Satellite Visibility: Statistics on the observation duration and signal strength for each satellite.

The following graph shows the results of data quality analysis performed on a RINEX file using our Compass Solution software.

Figure 4. Example of Data Quality Check Results from Compass Solution Software