Gps on EARTH Magazine

Observing a plate boundary

Wed, 23 Apr 2014 07:48:13 -0400

Credit: UNAVCO

More than 280 continuous GPS (cGPS) stations in Cascadia are part of the U.S. Plate Boundary Observatory (PBO), a component of EarthScope, which includes more than a thousand cGPS stations arrayed across the western United States and Alaska. Operated by UNAVCO, PBO provides continuous data to researchers studying tectonics and earthquakes. Each PBO station operates autonomously to record and transmit up to one sample per second. In addition to PBO, the U.S., New Zealand, Japan and Canada have implemented similar networks of cGPS stations with the intent of capturing both slow and rapid motion. By combining simultaneous data from multiple receivers, scientists can use cGPS networks to produce positioning and ground motion data with millimeter precision. Data from continuous stations can be blended with campaign studies, many of which share a fleet of GPS receivers managed by UNAVCO, to provide an effective tool for seismic research.

A truly global system

Wed, 23 Apr 2014 07:43:02 -0400

Credit: Kathleen Cantner, AGI

Like the GPS navigation system in your car or smartphone, a high-precision GPS receiver uses signals from satellites to determine the distance from the receiver to the satellite. But that’s where the similarities end. Today’s scientific and commercial-grade GPS receivers use two frequencies and carrier phase measurements (distance expressed in units of cycles of the carrier frequency) to produce precise results. In addition to the U.S. GPS satellites, many receivers use data from Russia’s GLONASS navigation satellites and are capable of using signals from the planned European (Galileo) and Chinese (BeiDou) systems. New U.S. satellites will provide an additional third frequency. The combination of the new and existing satellites is collectively known as the Global Navigation Satellite System, or GNSS. GNSS will provide significant benefits to commercial applications such as surveying, agriculture and construction, as well as earth science research.

A new tool for atmospheric studies

Wed, 23 Apr 2014 07:31:18 -0400

Scientists are putting GPS to work in some unexpected new ways. For example, John Braun, a project scientist at the University Corporation for Atmospheric Research (UCAR) in Boulder, Colo., is using GPS to measure precipitable water vapor.

Precise to a fault: How GPS revolutionized seismic research

Mon, 14 Apr 2014 12:57:55 -0400

The Global Positioning System is a constellation of more than 30 satellites orbiting Earth twice a day at an altitude of more than 20,000 kilometers. Geoscientists use GPS to make precise measurements of position and ground motion. Credit: Kathleen Cantner, AGI

In the late 1980s, Ken Hudnut, a Columbia University graduate student studying plate tectonics in Southern California, began experimenting with a new technology, called the Global Positioning System (GPS), as a way to measure the slow, relentless motion of Earth’s crustal plates.

Satellites can detect underground nuclear explosions

Wed, 05 Dec 2012 12:15:52 -0500

SAN FRANCISCO: If you’re looking for hints of an underground nuclear explosion, the last place you might think to look is up. But it turns out that the sky is a great place to look for clues, because satellites provide scientists with a way to locate the waves that clandestine weapons tests emit into the upper atmosphere, scientists announced yesterday.

Benchmarks: May 29, 1919: Solar eclipse "proves" relativity

Thu, 05 Jan 2012 06:41:58 -0500

On May 29, 1919, the moon’s silhouette crept slowly over the sun, bringing premature night to observers in a broad swath of the Southern Hemisphere between South America and Africa. Few onlookers realized that this event would provide the first successful test of Albert Einstein’s theory of relativity.

The rise of community remote sensing

Thu, 05 Jan 2012 06:41:58 -0500

If you ask someone involved in community remote sensing to define the emerging field, the most likely response will be a chuckle followed by “That’s a hard question to answer…”

Bill Gail, a director at Microsoft’s Startup Business Group in Boulder, Colo., coined the term, and he says he likes to keep the definition “nebulous” as the field takes shape. At its core, the movement is about remote sensing — collecting data from afar. Remote sensing “has revolutionized science and Earth monitoring,” Gail says. Airplanes, satellites, space probes and the like have helped scientists gather information on long-term, global scales, but these tools have limitations: They fail to capture what’s happening at the local level, he says.