Triple frequency Global Navigation Satellite Systems (GNSS) will be operational in the next few years. The availability of a third frequency allows to develop several innovative techniques. We can cite triple frequency multipath analysis [1] or furthermore triple frequency ambiguity resolution algorithms, like Three Carrier Ambiguity Resolution (TCAR) for Galileo or Cascading Integer Resolution (CIR) for GPS [2]. Our goal here is to develop an improved Total Electron Content (TEC) monitoring technique based on triple frequency GNSS measurements. Firstly, we have developed a triple frequency simulation software, which enable us secondly to develop and test the three steps of the technique on realistic Galileo and GPS measurements. In this method, code measurements are onldy used in the preliminary step. As a consequence, because it is not affected by code hardware delays, the precision of the reconstructed TEC would be improved in regards with the usual dual frequency technique [3]. As the ionospheric delay –which mostly depends on the TEC– remains the main limitation of GNSS precision and reliability, an improved modelling of the TEC will allow to increase the precision and reliability of several GNSS navigation and positioning techniques.