They are carried along with the Highwater Trousers' activation code by the ghoul scientist in SatCom Array NW-05a. The tapes add the map markers for the SatCom Array NN-03d and SatCom Array NW-07c to the Pip-Boy world map after they've been activated on the satellite control terminal on the array's top level.
SatCom array NW-07c coordinates
SatCom Array NW-07c
SatCom array NN-03d coordinates
SatCom Array NN-03d