**Appendix A. Data Storing and Conversion**

Data were stored in the binary U-blox logging format (\*.ubx) on a local SD card of the Raspberry Pi. The logged files consisted of the UBX-RAWX messages which contained the raw measurements of the receiver (pseudorange, carrierphase, doppler and SNR on all recorded frequencies and satellite systems). The sampling interval was 1 Hz. Data were stored in 24 h batches of .ubx log files. For further processing, the data were converted to daily, 1Hz RINEX3 files. This step was performed with a combination of the RTKLIB application convbin (v. 2.4.3) and gfzrnx (v. 1.11) [36]. Figure A1 represents the work flow of this process. Metadata, if available, were added to the generated data.

**Figure A1.** Sketch of \*.ubx data format conversion to RINEX version 3.
