GNSS Markets and Applications - Understanding GPS: Principles and Applications - page 659

Figure 12.7 NovAtel GPS L5 FPGA card modified for GALILEO L5. (Courtesy of NovAtel.)

part of an integrated navigation system, so they may have very different interfaces
than the chipsets.
Receivers for the marine navigator have very different outputs than ones found
in aircraft. Typical marine outputs are used to guide ships over great circle, rhumb
line routes, and ocean sea lanes. Most marine receivers include the capability to pro-
cess corrections from the NDGPS system through a serial port connection or via an
internal low-frequency radio. Calculations of latitude and longitude, speed, and the
like are standard outputs for maritime equipment.
Aircraft outputs are typically those found in any flight management system,
such as range and bearing to the next VOR station. In addition, aircraft receivers
must meet very stringent hardware and software standards set down by the FAA.
They are designed to receive WAAS broadcasts and LAAS data.
Survey receivers are a different breed. They are sometimes known as RTK
receivers and rely on carrier-phase measurements, usually in some sort of a differen-
tial mode of operation. Here the most important requirements are for accuracy,
often subcentimeter and for very rapid reacquisition of signals whenever there is an
outage. Chapter 8 provides extensive details on RTK.
Still more rigorous requirements are found in military receivers. Manufacturers
in this segment tend to serve only this segment. Some commercial manufacturers,
notably Trimble Navigation and GARMIN also sell ruggedized units to the mili-
tary. However, their military offerings, for the most part, are derived from their SPS
equipment, with little special development for the military. Timble's Y code cards
are an exception to that generalization.
Like all military equipment, GPS receivers must meet stringent environmental
specifications as well as high-accuracy, antijam, fast fix, security, and so on. Mili-
tary receivers operate on C/A and Y code on both the L1 and L2 frequencies. Future
versions will receive M code as well.
An important receiver component is the GPS antenna. Oftentimes it limits per-
formance of the receiver. Some installations, such as cell phones and handhelds,