§ 004. How to merge / combine RINEX files?

Intro

Sometimes, one may have in hands set of RINEX observables files w/ GNSS measurements (say 1-hour files). However, one single "composite" RINEX file is needed. The very first idea might come is to concatenate files one by one to the end of result file. However, it is not good idea. Primary reason is RINEX file Header. Composite file should contain one header updated by all the information available in merged files.

Moreover, there are many pitfalls if one would dig deeper. Let us imagine, that 1st 1h file includes measurements for GPS L1CA and L2P but starting from 2nd 1h file there is also L1C measurements available. It means that RINEX header of merged file must include information about availability of all these 3 x signals. Nothing to say about corresponding modification of measurements information for every epoch by adding empty slots / offsets.

In result, simple ‘merging’ as it was seen at first glance turns to quite complex operation requires decoding and epoch-by-epoch analysis of all merged files and re-creating new RINEX file from the very beginning. One also should keep in mind that files to be merged may be of different formats (RINEX2, RINEX3, RINEX4, Hatanaka Compressed) and merging utility should be able to manage all of them.

KernelSAT offers RINEX Tools online service which could do all these jobs for you.

Few words about RINEX Tools

RINEX Tools is online WEB service allowing to merge & combine RINEX files. Processing includes final RINEX header modification w/ all the information (time start / stop, available GNSS, signals, data types) collected from all the merged files.

Also RINEX Tools can do:

• Convert RTCM3 corrections into RINEX format
• Convert RINEX files from one version to another one. For instance, from version 2 (RINEX2) to version 3,4 (RINEX3, RINEX4) or vice versa.
• Modify RINEX files by applying decimation (say, convert 1 sec file to 15 sec file) or by removing concrete GNSS, Signal, satellites.

Example of how to merge RINEX

Let's demonstrate practical example of RINEX file merging. Imagine, there are 6 1-hour RINEX files of RINEX2 type. But we need single merged file of version RINEX3.

Well, first go to RINEX Tools Home Page and start new session.

Choose Merge (combine) RINEX files option at first step of processing Wizard. Than press Next button.

Next choose the files to be merged.

Once done, press Next button.

Here one may set-up some settings to be applied on result merged RINEX file. One may choose output RINEX version (in our case we need RINEX3), apply decimation and remove (if needed) GNSS systems.

Next wizard step allows us to check list of files to be merged and settings to be applied. Before proceed next (Upload button), security code is to be entered as well.

File uploading and processing starts on the next step. Please be patient, it may take some time especially for huge bulky files.

Result merged RINEX file is ZIPped on server side and automatically downloaded once ready. If it is unzipped, we may see one result file of bigger size (6 x 1-hour file merged + converting from RINIX2 to RINEX3.

One may check content of result RINEX file via some advanced text editor (for instance, NopePad++) if the file is not too huge.

     3.05           OBSERVATION DATA    MIXED               RINEX VERSION / TYPE
RTOOLS              KernelSAT           20240111 100335 UTC PGM / RUN BY / DATE
KernelSAT Rinex Tools                                       COMMENT
Input file: gaby010a.24o                                    COMMENT
Input file: gaby010b.24o                                    COMMENT
Input file: gaby010c.24o                                    COMMENT
Input file: gaby010d.24o                                    COMMENT
Input file: gaby010e.24o                                    COMMENT
Input file: gaby010f.24o                                    COMMENT
                                                            COMMENT
Lonnie Sears        EGPSSO                                  OBSERVER / AGENCY
QB1029280057        CHAMPION_QB1        5.21                REC # / TYPE / VERS
3198102             ARFAS13DFS      ARFS                    ANT # / TYPE
        0.0000        0.0000        0.0000                  ANTENNA: DELTA H/E/N
GABY                                                        MARKER NAME
GABY                                                        MARKER NUMBER
   481172.7340 -5429086.0760  3301740.1670                  APPROX POSITION XYZ
  2024     1    10     0     0    0.0000000     GPS         TIME OF FIRST OBS
  2024     1    10     5    59   55.0000000     GPS         TIME OF LAST OBS
     5.000                                                  INTERVAL
RTools: Total 6 file(s) processed                           COMMENT
G    7 C1C L1C S1C C2W L2W S2W C2C                          SYS / # / OBS TYPES
R    8 C1C L1C S1C C1P C2P L2P S2P C2C                      SYS / # / OBS TYPES
    37                                                      # OF SATELLITES
   G02   112   112   112   112   112   112     0            PRN / # OF OBS
   G03  1297  1296  1296  1296  1296  1296  1296            PRN / # OF OBS
   G05  2636  2636  2636  2636  2636  2636  2636            PRN / # OF OBS
   G06  4197  4197  4197  4197  4197  4197  4197            PRN / # OF OBS
   G09  1821  1818  1818  1818  1818  1818  1818            PRN / # OF OBS
   
........

There is one extra WAY of how to quickly get general statistic about RINEX file. Below are the part of WAY service statistic for two files: from left side - one of the original files to be merged (gaby010a.24o). On the right side - statistic for resulted merged file by RTools (gaby0100.24o).

Summary

The article provides step-by-step example of how to combine RINEX files w/ help of KernelSAT RINEX Tools (RTools) online service. Merged RINEX file contains header updated by all the information obtained form files to be combined including GNSS, Signals and observables types. RINEX Tools also allow to convert resulted file to required version of RINEX.