Going Public - GPS Declassified: From Smart Bombs to Smartphones - page 98

Fig. 6.3. gps Block iia satellite. (Courtesy National Coordination Office for Position, Navi-
gation and Timing)
differences in signals received at one or more (static) base stations, or precisely
known, surveyed positions, with signals from receivers at other, unknown posi-
tions, including moving (kinematic) receivers. The development of “differen-
tial gps” greatly enhanced accuracy and led the way toward land-based
augmentation systems that improve navigational accuracy around marine ports
and airports.
Smaller, Lighter, and Faster
In 1988 three companies introduced gps receivers small enough and light
enough to hold in one hand. Rockwell Collins, a defense contractor for both
gps satellites and receivers, demonstrated a prototype of the first compact,
all-digital receiver, dubbed “Virginia Slim” after a popular cigarette brand