Tech Chat | What is RINEX?

2022-08-02

Static survey is the most basic survey method of GNSS receivers, which can achieve millimeter-level accuracy after post-processing. Surveyors should be very familiar with the RINEX data format, as it is the most common and standard raw data format for static surveys.

So how is the RINEX format defined and how to use it with GNSS receivers?

What is RINEX?

RINEX is short for Receiver Independent Exchange Format. As the name implies, this format is widely used in the GNSS field and is a standard data format.

The RINEX format uses TEXT file (ASCII code) to store data. The data recording format is independent of receiver manufacturer and model, which facilitates data transfer and makes data as widely used as possible.

The RINEX data formats currently in common use are RINEX2.x and RINEX3.x.

1. RINEX 2.x

1.1 Data Type

Taking RINEX2.11 as an example, six data types are defined:

(1) O file: Satellite observation value file
(2) N file: GPS navigation message file
(3) G file: GLONASS navigation message file
(4) M file: Surface meteorological data measured at the station
(5) H file: GEO navigation message file
(6) C file: Satellite and receiver clock file
(7) L file: Navigation message of Galileo
(8) S file: TEQC quality test file

Among above, the O, N and M files are the most common. O and N files are required for data processing and analysis.

1.2 File Name

The RINEX2.x file is named SSSSDDDHMM.YYT

(1) SSSS stands for station name
(2) DDD stands for annual cumulative days
(3) H is the hour of the day.
(4) M is the minute of the hour
(5) YY refers to the last two digits of the year; for 2022, YY is 22
(6) T represents the data type, such as O, N, and M

Such as Y11L021791781030.22O, Y11L02179 is the station name, 178 is the 178th day of the year, 1030 means at ten thirty minutes, 22 is the year of 2022, O means O file. However, many programs now support changing RINEX filenames, so you can define the filename according to your own habits.

1.3 File Content

Take O files as an example. Each O file is divided into a header file and data. From the first line to "END OF HEADER" is the part of the header file. The most right side of each line is the header file description section, where the important information is the receiver model, antenna height and approximate coordinates.

Header file section:

Just look at the comment on the right of each line:

(1) Receiver model: the second item of REC # / TYPE/VERS
(2) Approximate coordinates: APPROX POSITION XYZ
(3) ANTENNA height: first term of ANTENNA: DELTA H/E/N

Data section:

This section lists the observation data of each satellite in all epoch. Locate the line "OBS TYPES" in the header file where the first number of each system (21) represents a total of 21 observations. So if you go to the data section, you'll see that this is a group of 21 numbers, corresponding to the 21 numbers from C1 to S6 in the figure above.

2. RINEX 3.x

Compared with RINEX 2.X, the RINEX 3.x format mainly changes the file content. Take RINEX 3.02 as an example:

The file is still divided into two parts, the header file and the observation data. The introduction of headers is mostly similar to the 2.11 version.
RINEX VERSION/TYPE indicates the file TYPE and navigation system TYPE. M indicates the mixed TYPE. MARKER NAME/MARKER NUMBER is some information about the station, not important. PPROX POSITION should be read each time it is used.

The following SYS / # /OBS TYPE is different from version 2.11.
First, look at the beginning of each line is G/R/C/E, which is the GNSS system code.
G – GPS, R – GLONASS, C – BDS, E- GALILEO, S – SBAS, J – QZSS, I – IRNSS.

Taking G as an example, G stands for GPS, 12 stands for observation type, followed by the specific observation type, which is more complex than version 2.11.

For the data section, RINEX lists specific observations for each observation type of each satellite in each satellite system.

How to use GNSS receiver to store RINEX data in different formats?

Here we use Y1 GNSS receiver as an example. Connecting the WiFi of the device through the computer, enter 192.168.1.8 in the browser, and then enter the configuration interface of the receiver. The user name is admin, and the password is admin.