RINEX 3.02

Using RINEX 3 as Base Corrections for RESEPI

Purpose: To understand how to use RINEX data as base corrections when processing data with Inertial Labs RESEPI PCMaster software.
Last Updated: January 2025

Many services providing RINEX data use the hourly format as a standard way of storing and transmitting data. However, unlike CORS (Continuously Operating Reference Stations) networks, such services often do not provide flexible settings for changing the duration of data intervals. Users have to merge hourly files themselves if they need to work with longer time intervals.

To demonstrate how to combine hourly RINEX files, let’s look at a few examples using popular tools, namely:

These utilities are available for download from official websites and are designed to work in the command line.

First, let’s look at unpacking “.crx“. A RINEX file in the “.crx” format is a compressed version of the standard RINEX (Compact RINEX). This format allows you to significantly reduce the size of files, which simplifies their storage and transfer. However, to work with such files, they must be unpacked into the standard “.rnx” format. To do this, place “.crx” and the unpacking utility in any desired directory, as shown in Figure 1.

Figure 1. Directory with the ".crx" file and the unpacking utility.

Then open PowerShell and enter the unpacking command, in our case it looks like this, Figure 2:

.\CRX2RNX.exe .\SEV100ESP_R_20250071100_01H_01S_MO.crx

Figure 2. Entered unpacking command in the "Windows PowerShell".

As a result, the unpacked Rinex file will appear in the folder, as shown in Figure 3.

Figure 3. The unpacked Rinex file appeared in the directory.

Now let’s look at merging several files into one. Let’s say we want to merge two ephemeris files and two observation files, as shown in Figure 4. As you can see, we placed the observation files and ephemeris in one directory, and also created a new directory “tmp“. It will be needed for temporary storage of the merged files.

Figure 4. Folder with files that need to be merged.

To merge, we will use the gfzrnx.exe utility. Before merging, you need to check the file version to avoid errors. In this case, we downloaded Rinex version 3.04. If you have a different version, for example 3.02 or 3.04, then you should take it into account as a parameter when merging.

Figure 5. Verison of Rinex.

Also open PowerShell and write the command, Figure 6:

.\gfzrnx.exe -finp .\SEV100ESP_R_20250071100_01H_01S_MO.rnx .\SEV100ESP_R_20250071200_01H_01S_MO.rnx -fout tmp\SEV100ESP_R_20250071100_01H_01S_MO.rnx -vo 3.04 -splice_direct

Figure 6. Command for merging several files.

Note that the name of the output file is the same as the first of the input files. For this purpose, the “tmp” directory was created, into which the combined file is placed. To avoid name conflicts. When combining hourly RINEX files, it is important that the resulting file (combined) has a name corresponding to the beginning of the first time interval. For example, if the first file covers data from 11:00 to 12:00 (SEV100ESP_R_20250071100_01H_01S_MO.rnx), and the second from 12:00 to 13:00 (SEV100ESP_R_20250071200_01H_01S_MO.rnx), then the combined file, including data from 11:00 to 13:00, should be called SEV100ESP_R_20250071100_01H_01S_MO.rnx

Navigation files are combined in the same way.

Let’s consider another case when the service provides hourly observation files and only one daily navigation file (‘EPHM00GBR_S_yyyyddd0000_01D_MN.rnx.zip’). This is also not a problem. Below is an example of using RINEX version 3.04 files from a public base station of the Ordnance Survey GNSS network, as shown in Figure 7.

Figure 7. Two hourly observation files and one daily navigation file.

Before merging, let’s look inside the navigation file. As shown in Figure 8, the versions are different. Therefore, when merging, we will “bring” the observation files to a newer version to avoid processing errors.

Figure 8. The daily navigation file and the daily observation file have different versions.

In this case, the command for merging will look like this, Figure 9:
./gfzrnx.exe -finp BIAX00GBR_S_20250081200_01H_30S_MO.rnx BIAX00GBR_S_20250081300_01H_30S_MO.rnx -fout tmp\BIAX00GBR_S_20250081200_01H_30S_MO.rnx -vo 3.05 -splice_direct

Figure 9. Merging two observation files.

As a result, a merged observation file will appear in the “tmp” directory. For correct processing, it is necessary to rename the navigation file according to the name of the observation file, as shown below:

EPHM00GBR_S_20250080000_01D_MN.rnx -> BIAX00GBR_S_20250081200_01H_MN.rnx

After renaming, move the finished files to the “data” folder of your project, for example, as shown in Figure 10.

Figure 10. Processed base station files in the project's "data" folder.

You can learn more about the command line parameters for the utilities used on the official websites. We will also leave useful links for a more detailed acquaintance with the Rinex format:

[1] RINEX File Naming Conventions RINEX 2 Format Files.

[2] Janssen, Volker. Senior Technical Surveyor in the Geodetic Operations Team at DCS Spatial Services.

For any additional questions, please email support@inertiallabs.com

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