Currently three up-to-date Terrestrial Reference Frames(TRF) are available, the ITRF2014 from IGN, the DTRF2014 from DGFI-TUM, and JTRF2014 from JPL. All use the identical input data of space-geodetic
Modeling Near Vertical Incidence Sounding(NVIS) High Frequency(HF) signal propagation in the ionosphere is important. Because, ionosondes which are special types of radars probing the ionosphere with