How many receivers must have a valid signal for Underwater GPS to function?

Underwater GPS will be able to calculate the position of the locator as long as at least three receivers obtain a valid signal from it. This is true both when using an antenna (which has four receivers built into it: one at the end of each of the three arms, and one pointing downwards in the middle) and when using separate receivers. In particular, if using separate receivers, it is possible to use only three rather than the recommended four.

However, obtaining a good signal at all four receivers will significantly improve the accuracy of the positioning, and we recommend to always try to position the antenna / receivers so that all four receive as good a signal as possible (the higher the "RSSI" which can be seen in the 'Diagnostic View' in the GUI, the better).