Where Are We? - GPS Declassified: From Smart Bombs to Smartphones - page 167

site's life span by improving compaction 10 percent across a half-million cubic
feet of available airspace. 152 Contractors dredging 130,000 cubic yards of mud
from the Ohio River near Mount Vernon, Indiana, in 2011 used a three-
dimensional gps system to “see” their bucket digging on the river bottom,
speeding the work and avoiding overexcavation. 153 Analysts estimate that about
40 percent of U.S. heavy and civil engineering construction firms have adopted
gps, producing $9.2 billion in cost savings annually. 154 gps-guided robots and
“smart machines” will increasingly affect other spheres of activity in the future,
a topic explored in the next chapter.
Scientists and engineers are adopting gps for a variety of environmental
uses, including monitoring bridges, earthquake fault lines, bird migration pat-
terns, and endangered species. Researchers in the United Kingdom demon-
strated in 2006 that gps sensors could detect bridge movements of less than
a centimeter. By establishing a baseline for bridge deflections due to traffic
loads, temperature, winds, and deterioration, gps sensors can alert authori-
ties when bridge movements exceed design tolerances. 155 Russian engineers
in 2011 installed sensors with dual glonass/gps receivers on a new 3,887-foot
cable suspension bridge—the world's longest—linking the far eastern city of
Vladivostok to Russky Island. 156 Such dual-signal receivers roughly double the
number of potential satellites visible, making them ideal for locations where
tall buildings, tree canopies, or bridge structures mask parts of the sky.
Like surveyors, geophysicists did not need the full complement of satellites
to begin monitoring fault lines using gps receivers bolted to solid rock at sur-
veyed positions in earthquake-prone areas. China installed its first gps earth-
quake monitors in 1985. 157 The Southern California Earthquake Center had
installed 350 monitors in the region by 1991. 158 A year after the January 17,
1995, earthquake in Kobe, Japan, that killed more than six thousand people,
the government doubled the number of gps monitoring sites across the island
nation to about one thousand. 159 gps sensor measurements before and after
the magnitude 8.8 earthquake that struck southern Chile on February 27, 2010,
showed that it moved the entire city of Concepción about ten feet west and
shifted Buenos Aires, Argentina—eight hundred miles from the epicenter—
about an inch. 160 Seismologists announced plans to add fifty sensors to the
twenty-ive already in the region. 161 The March 11, 2011, magnitude 9.0 earth-
quake of the coast of Japan that caused devastating tsunami waves intensified
the search for faster analysis and earlier warnings. Initial reports underesti-
mated the magnitude as 7.1 because severe shaking often saturates seismom-