The Garmin GPS16x HVS (27) was selected as it is IPX7 rated and has a built-in antenna. The device is interfaced with messages that follows the NMEA0183 protocol. Baud rate is not defined in the NMEA standard. The baud rate can be set to 4800, 9600, 19200 or 38400. Lower baud rate increases immunity against radio frequency interference (RFI) but requires more time for transfer. 38400 was selected and tested. The device follows RS-232 defined voltage levels but also supports TTL voltage levels. The device does not support polling but outputs the selected messages at a frequency of 1 Hz. The user can enable or disable the different available messages. The available NMEA-approved output sentences are: GPALM, GPGGA, GPGLL, GPGSA, GPGSV, GPRMC, GPVTG. In addition, the device can provide the following Garmin proprietary sentences: PGRMB, PGRME, PGRMF, PGRMM, PGRMT, and PGRMV. In order to be able to meet system requirement A.REQ.2.06.4, GPRMC was enabled. GPRMC provides SOG, COG, and position. The GPGGA message enabled in addition because it provides the following useful information: Signal quality, number of satellites with fix and horizontal accuracy of position.

The RockBLOCK device is IP68 rated and hosts an Iridium 9602 unit, an antenna and a voltage regulator. The 9602 unit is interfaced with RS-232 using AT commands. Depending on the conditions, the unit can send or receive a message approximately every 40 seconds. The cost is 0.1 to 0.05 GBP per 50-byte message, depending on the bundle that is bought. In addition, there is a 10 GBP line rental per month. The system has a limited bandwidth and is therefore only suitable for simple control monitoring or tracking applications. The maximum package sizes are 340 bytes for sending and 270 bytes for receiving. Although the latency is typically a few seconds, it may be as much as a minute or more.