What differentiates an external GPS sensor from an external GPS antenna?

[Chuck - Raymarine - Moderator]

What differentiates an external GPS sensor from an external GPS antenna?

External GPS sensors (ex. Raystar 150, Raystar 130, Raystar 125, etc.) combine a GPS antenna and GPS receiver within a single housing. GPS sensors transmit processed GPS data (latitude, longitude, COG, SOG, etc.) using NMEA 2000, NMEA 0183, SeaTalkng, SeaTalk, or other proprietary communications formats to support the needs of a marine electronics system. In contrast to GPS sensors, GPS antennas have no data processing capability. GPS antennas are designed to gather GPS satellite transmission signals and pass these signals to a GPS receiver such as those embedded within an AIS650, a9x MFD, a12x MFD, eS9x MFD or eS12X MFD. Both GPS sensors and GPS antennas are designed to be installed in locations where they will be afforded an unobstructed view of the skies overhead to maximize sensed GPS signal strength.

While the designs of many currently manufactured Raymarine MFDs feature internal GPS sensors, it is sometimes necessary to network these MFDs to an external GPS sensor or connect a GPS antenna to the MFD's GPS antenna socket (at the time of this response, only Raymarine's a9x, a12x, eS9x, and eS12X MFDs featured a GPS antenna socket). The most common reason for installing an external GPS sensor or GPS antenna is that the MFD doesn't feature an internal GPS sensor (ex. e165 MFDs, gSx MFDs, E-Series Widescreen MFDs, C/E-Series Classic MFDs, etc.) or the MFD's installation location does permit it to receive sufficient GPS satellite signal strength to acquire and/or maintain an accurate GPS FIX. This condition may occur if the MFD is installed in a location which does not afford it an unobstructed view of the skies overhead.

Like the Raymarine's MFD's, Dragonfly Pro Displays and Dragonfly 6/7 Displays also feature an internal GPS receiver. These Dragonfly products have been designed to primarily support the fishfinding and basic GPS/Chartplotter needs of open boats. Like MFDs having internal GPS sensors, installation of a Dragonfly display within a pilothouse or beneath structures which prevent product from having an unobstructed view of the skies overhead may reduce the GPS signal strength received by the display's GPS receiver to a level below that which it can acquire, maintain, or provide an accurate GPS position FIX. However, while MFDs may be interfaced to an external GPS sensor, Dragonfly displays lack the communications interface(s) to which an external GPS sensor may be interfaced. Accordingly, those desiring CHIRP (conical) sonar / DownVision sonar fishfinder and GPS/Chartplotter features for applications where the display will not be afforded an unobstructed view of the skies overhead are typically recommended to consider installation of an Axiom DV MFD, Axiom RV MFD, eSx8 MFD, or ax8 MFD (retired). Upon installation of one of the above listed MFDs, should it be determined that the vessel's structure is reducing the GPS signal strength received by the display's GPS receiver to a level below that which it can acquire, maintain, or provide an accurate GPS position FIX, then an external GPS sensor or external GPS antenna may be mated to the MFD.


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