RINEX Observation Basics

RINEX observations, in brief

RINEX is an exchange format for GNSS observations and navigation data. An observation record identifies the satellite, signal and epoch: C1C is a code pseudorange in metres, while L1C is carrier phase in cycles. The header's observation order and time system determine how the numerical fields must be interpreted.

Prepared by OpenGNSSLabUpdated 30 September 2026Sources, reproducibility and corrections

Learning objectives

Identify the RINEX header and observation section.
Decode common observation type labels.
Map epoch rows to satellite measurements.

What a RINEX observation file stores

RINEX is a receiver-independent text format for GNSS observations. Observation files store measurement epochs, receiver and antenna metadata, observation type definitions, and per-satellite measurements.

The same file can contain GPS, GLONASS, Galileo, BeiDou, and other systems.

Important header fields

Field	Example	Meaning
RINEX VERSION / TYPE	3.04 OBSERVATION DATA M	Version, observation file, mixed GNSS.
APPROX POSITION XYZ	1130752.1541 -4831349.1034 3994098.9626	Approximate receiver ECEF position.
SYS / # / OBS TYPES	G 18 C1C L1C S1C ...	Observation columns for each constellation.
INTERVAL	30.000	Sampling interval in seconds.
TIME OF FIRST OBS	2024 1 1 0 0 0.0000000 GPS	Start time and time scale.
LEAP SECONDS	18	UTC to GNSS time context.

Raw data excerpt

Annotated RINEX observation excerpt

sample.obs

hover or focus fields

1     3.02RINEX versionThis file follows RINEX 3.02 formatting.           OBSERVATION DATAFile typeObservation files store measured code, carrier, Doppler, and signal strength values.    M (MIXED)Satellite systemMixed constellation file: GPS, GLONASS, Galileo, BeiDou, and others can appear.           RINEX VERSION / TYPE5ch151Marker nameStation or marker identifier written by the receiver/converter.                                                       MARKER NAME11  3246374.5864Approx XApproximate receiver ECEF X coordinate in meters.  4052665.3939Approx YApproximate receiver ECEF Y coordinate in meters.  3693176.0609Approx ZApproximate receiver ECEF Z coordinate in meters.                  APPROX POSITION XYZ13GSystemG means GPS. Each constellation declares its own observation columns.   16Observation countThe GPS rows have 16 observation types in this file. C1CC1CGPS L1 C/A-code pseudorange, in meters. This is a common SPP input. L1CL1CCarrier phase on L1 C/A tracking, in cycles. D1CD1CDoppler observation on L1 C/A, in Hz. S1CS1CSignal strength for L1 C/A, commonly in dB-Hz. C2W L2W D2W S2W C2S L2S D2S S2S C5Q  SYS / # / OBS TYPES22     1.000IntervalThe observation sampling interval is 1 second.                                                  INTERVAL23  2024    11    14    08    42   39.0000000First observation timeFirst epoch timestamp in the declared time scale.     GPSTime scaleThis timestamp is in GPS time.         TIME OF FIRST OBS50                                                            END OF HEADEREnd of headerObservation records begin after this line.51>Epoch markerRINEX 3 observation epochs start with the > marker. 2024 11 14 08 42 39.0000000Epoch timestampMeasurement time for all following satellite rows until the next epoch marker.  0Event flag0 means a normal observation epoch. 35Satellite countNumber of satellite rows listed for this epoch.       0.00000000000053G04Satellite PRNGPS satellite PRN 04.  21026994.340C1C pseudorangeFirst GPS observation column declared in the header: code pseudorange in meters. 8 110497599.986L1C carrier phaseCarrier phase observation in cycles. 8     -1326.004D1C DopplerDoppler value for the same signal. 8        48.422S1C signal strengthSignal strength in dB-Hz. 8  21026999.531 9  86102041.976 9     -1033.281 9        56.226 9  21026999.777 8  86102046.973 8     -1033.223 8        53.109 8

Excerpted from a real RINEX observation file. Only the educational snippet is embedded; the full raw file is not published as a site asset.

Observation type codes

Code	Meaning
C	Code pseudorange
L	Carrier phase
S	Signal strength
1, 2, 5, 6, 7, 8	Frequency band
C, P, W, X, I, Q, Z	Signal tracking/channel type

Epoch and satellite rows

> 2024 01 01 00 00  0.0000000  0 34        .000000015974
G01  20888756.039   109771298.977 8        48.750    20888756.369 ...
G02  23201822.669   121926668.150 7        43.250    23201822.179 ...

How to read the epoch

The epoch line starts with `>` and gives the timestamp, event flag, number of satellites, and optional receiver clock offset.

Each following satellite row begins with a system letter and PRN, then measurement values in the exact order declared by that system's header observation-type line.

Example measurement columns

Satellite	C1C	L1C	S1C	C1W	L1W	S1W
G01	20888756.039	109771298.977	48.750	20888756.369	109771289.968	43.000
G02	23201822.669	121926668.150	43.250	23201822.179	121926528.154	34.750

Common mistake

Do not assume every satellite row has the same columns across constellations. GPS, GLONASS, Galileo, and BeiDou can each declare a different observation-type list.

What you should understand now

The header tells you how to interpret every numeric row.
Epoch rows organize observations by time.
SPP usually begins by selecting code measurements such as C1C for enough satellites at one epoch.

References

RINEX 3.04 format specification

Help improve this tutorial

Point out numerical ambiguity, missing prerequisites, or a step that needs a fuller derivation.