November/December 2006

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Robbing banks is still a popular pastime in the United States. After all, that’s where the money is. But sometimes the crooks get away with a little more than they’d figured on.

The Global Positioning System has gotten along without leap seconds for nearly 30 years, and if GPS system time — which drives the phones, the power grids, the Internet, and even more important, the banks — can get along without it, that’s fine by me.

Measuring variations in the Earth’s gravity field has practical implications for commercial exploration for natural resources as well as advancing geophysical knowledge. The value of gravimetric methodology relates directly to the precision of spatial resolution derived from the measurement instruments. For years, researchers have used the complementary technologies of GNSS positioning and inertial sensors to refine their methods. Today, new data-processing algorithms and the advent of Europe’s Galileo system promise new advances in these techniques.