Weather Permitting - GPS Declassified: From Smart Bombs to Smartphones - page 32

The chronometer, then costing about fifty pounds, was considered too expen-
sive by American mariners. For example, the Brig Reaper voyaged in 1808 from
America to Calcutta to buy coffee using inertial navigation and lunars. By 1850,
chronometers became so inexpensive that the use of lunars disappeared.
The discovery of radio waves in the second half of the nineteenth century
quickly became important to navigation. Scottish physicist James Clerk Max-
well mathematically predicted radio waves in 1864, and Heinrich Hertz, a
physics professor at Karlsruhe Polytechnic in Germany, proved their existence
by engineering instruments to transmit and receive them in 1887. Italian inven-
tor Guglielmo Marconi and Serbian-American inventor Nikola Tesla both
devised methods of wireless communication using radio waves. The British
tracked the German fleet in the 1916 Battle of Jutland using radio direction-
finding techniques. Radio engineers also recognized the feasibility of using
radar for navigating ships or airplanes. Radar navigation is the reverse of track-
ing objects; the same reversal occurred in moving from tracking satellites to
using them for navigation (see chapter 3).
The speed of airplanes accentuated navigational challenges, especially for
solo pilots. There was no time for twenty-minute lunar calculations, and if
there had been, the plane's speed prevented calculating a current position.
U.S. Navy captain Philip Van Horne Weems pioneered methods for faster air-
borne navigation using mechanical devices. He invented a special watch for
accurately determining Greenwich mean time, improved the sextant, and estab-
lished a company, Weems & Plath, to market his navigational aids. 14 Along the
way, he befriended prominent pilots such as Charles Lindbergh and the more
controversial “Wrong Way” Corrigan, who claimed that he flew from New
York to Ireland instead of Los Angeles due to misreading his compass. N. W.
Emmot, in “The Grand Old Man of Navigation,” an article based on an inter-
view with Weems, notes that invoice records show that the information and
charts Weems sold Corrigan were all about the North Atlantic. Another Navy
aviator, Capt. Charles Blair, planned to fly in 1951 across the North Pole in a
modified p-51 Mustang. Weems plotted in advance the sun's altitude for points
along the entire flight, allowing Blair to compare his sightings to a graph with-
out performing computations while flying.15 15 In the 1960s, early position cal-
culations using the space navigation approach utilized in gps required
extensive manual work. Today, miniature computer processors perform such
calculations instantaneously on a smartphone or a dedicated gps receiver.
“The current almost universal utilization of gps owes as much to advances in