GTEX

GTEX: The GNSS-TEC Exchange Format

The purpose of the GTEX (GNSS-TEC Exchange Format) is to share slant TEC data from each receiver. By sharing slant TEC data which are not converted to vertical TEC, various ionospheric studies may be possible without affected by specific analysis procedures such as satellite/receiver bias estimation, or different mapping heights. Thus, slant TECs include biases arising from inter-frequency bias of satellites and receivers. The structure of GTEX is designed in such a way that the structure is as close to RINEX (Receiver Independent Exchange Format) as possible, because RINEX is a de facto standard in exchanging GNSS observation data and potential users of GTEX would be familiar with RINEX. GTEX may include more data relevant to TEC analysis in the later revisions. The format is designed to allow future extension. The GTEX was first proposed as a format to promote international exchange and sharing of GNSS-TEC data as a contribution paper to meetings of Working Party 3L (ionospheric propagation and radio noise), Study Group 3 (SG3, radiowave propagation) of ITU-R in June 2013 at Geneva, Switzerland. The GTEX format was approved as one of the standard data of trans-ionospheric data and included in Recommendation ITU-R P.311-16 Annex 1 in 2015. If you have any questions or comments, please e-mail to .

General Description

The GTEX data file consists two parts, the header and the TEC data blocks.
The header block structure is similar to that of RINEX 2. All the header items defined in RINEX 2 can be used in GTEX as well. Two observation type descriptors, “TR” for slant TEC including bias (“raw TEC”) and “TF” for TEC status flag, are introduced. There is an additional header item to describe the unit of TEC.
The TEC data block starts from a line(s) with a time stamp and list of satellites with the same format as “EPOCH/SAT” field of RINEX 2. Following the EPOCH/SAT field, TEC data as defined in “# / TYPES OF OBSERV” are recorded. After the record of TEC data for all the satellites, data set of the next epoch follows. The actual format descriptions as well as some examples are given here.

Data Conversion Tool

"RNX2GTEX" is an application to convert GPS/GNSS data to GTEX TEC data. RNX2GTEX for Linux/Unix consists in a set of programs written in fortran 77 and a shell script. The RNX2GTEX for Linux/Unix is available from here. The tar file includes RNX2GTEX directory, in which there are README, a shell script (RNX2GTEX.sh), Makefile and fortran source codes. Please refer to README for more details. RNX2GTEX for Windows is an application for creating GTEX data files from RINEX data using explorer-like GUI. Please refer to User Guide. Please contact to for downloading latest version of RNX2GTEX for Windows.