This activity is intended to investigate the Grazing Angle (GA) Carrier Phase Altimetry (CaPA) using signals transmitted by the Global Navigation Satellite Systems (GNSS). The CaPA technique requires that the electromagnetic signal reflects coherently rather than in a diffuse regime. The hypothesis is that GA geometries enhance the likelihood of coherence scattering. It was also hypothesized that the combination of signals at slightly different frequency bands could expand the coherence conditions (widelane techniques, WL). The CaPA is a precise technique, as it is only possible when the carrier phase can be tracked, that is, when the electromagnetic wave can be measured at a fraction of a cycle. At L-band, with cycles corresponding to ~20 cm length, this maps into a few cm delay precision. Nevertheless, the use of carrier phase delay measurements tends to be relative rather than absolute (delay variations).