Weather Permitting - GPS Declassified: From Smart Bombs to Smartphones - page 33

microprocessors as to progress in the central system itself,” observed Dr. Alex-
ander H. Flax, who served as chief scientist for the Air Force from 1959 to 1961
and as director of the National Reconnaissance Office from 1965 to 1969. 16
Engineers at the Lorentz Company in Germany fielded the first electronic
guidance system for low-visibility aircraft landings. 17 In 1940 the Germans
sent bombers over Britain at night using two radio waves sent from the same
station 180 degrees out of phase (peaks and valleys canceling each other out).
When the bombers received no signal, it meant they were in the area where
the waves overlapped and were headed toward the target city. 18 They also used
a director beam, which the bomber would follow and then drop its bomb when
it hit a cross beam.
Loran, for long-range navigation, was a system that developed out of the
British Gee system, a land-based pulse radar that transmitted signals from
towers in different positions. For a given time differential between the receipt
of the signals, the receiver's position could be specified on a hyperbola. Thus,
a receiver requires signals from another pair of stations in order to obtain a
position fix. The system was improved when Loran-A was replaced by Loran-
C, which operates at a lower frequency and is able to transmit signals over the
horizon.
The next chapter covers the different space-based navigational system pro-
posals in which satellites replaced land-based towers. After World War II, rocket
pioneers in the United States and the Soviet Union built on the achievements
of Wernher von Braun's German team, which developed the v-2 rocket. As
noted in chapter 1, von Braun led the Army program that launched the first U.S.
satellite. Space visionaries saw the potential for satellites to provide worldwide
communications and navigation guidance unhindered by the “vicissitudes”
of weather that have affected other techniques through the ages. Many people
made navigation proposals; ultimately the Global Positioning System was for-
mulated and revolutionized navigation. The potential problem today is over-
dependence on gps, not finding uses for it.