The Global Positioning System, usually called GPS, is the only fully-functional satellite navigation system. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio to GPS receivers, allowing them to accurately determine their location (longitude, latitude, and altitude) in any weather, day or night, anywhere on Earth.

GPS has become a vital global utility, indispensable for modern navigation on land, sea, and air around the world, as well as an important tool for map-making, and land surveying. GPS also provides an extremely precise time reference, required for telecommunications and some scientific research, including the study of earthquakes.

United States Department of Defense developed the system, officially named NAVSTAR GPS (Navigation Signal Timing and Ranging GPS), and the satellite constellation is managed by the 50th Space Wing at Schriever Air Force Base. Although the cost of maintaining the system is approximately US$400 million per year, including the replacement of aging satellites, GPS is available for free use in civilian applications as a public good.

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USGS Newsroom

Science that Weathers the Storm: Track Flooding During Tropical Storm Gustav in Real-Time
OC_Web@usgs.gov (Office of Communications Web Group) Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Reporters: Want to accompany a USGS crew as they install mobile gages or storm surge sensors? Contact Brian McCallum at 404-375-2505 or bemccall@usgs.gov. Real-time flooding and storm surge information is available as Tropical Storm Gustav approaches the Gulf Coast by visiting the interactive US Geological Survey (USGS) Water Hazards Map. The map provides flooding and storm surge data from Gulf Coast streamgages, which is imperative to local, State and Federal officials in order to forecast floods and coordinate flood-response activities in the affected area. "We could not accurately forecast river flows and water-levels without the data and support we receive from the USGS," said Dave Reed, Hydrologist-In-Charge of the National Weather Service Lower Mississippi River Forecast Center in Slidell, LA. "When river and tide data are not available, our job of forecasting is much more difficult and typically results in diminished accuracy of those forecasts." The USGS, in collaboration with the U.S. Army Corps of Engineers, New Orleans District, has just installed five new strengthened, or "hardened," tidal gages along the Louisiana Gulf Coast and Mississippi Sound. These gages were designed to withstand a category 4 hurricane storm surge. Real-time data from hardened gages, as well as and storm-surge sensors and rapidly-deployable mobile gages will also be accessible on the USGS Hazards Map on a Google Map interface. Access other USGS Tropical Storm Gustav efforts by visiting the USGS Gustav storm site. USGS scientists will install rapidly-deployable mobile gages and storm-surge sensors starting tomorrow. Real-time data from these devices will also be visible on the hazards map. These temporary gages provide additional real-time monitoring data in critical areas needed for effective forecasting and emergency response. Rapidly deployed mobile stations provide special, short-term data in critical areas lacking long-term streamgages. These mobile real-time stations will help emergency needs and improve coastal flood forecasts. They provide up-to-the-minute data that is critical to the National Weather Service and other partners involved in issuing flood warnings and the evacuation of communities. USGS also has a network of rugged, inexpensive water-level and barometric-pressure sensors, called storm-surge sensors, which are ready to be installed right before Gustav hits land. These sensors provide information about storm surge duration, times of surge arrival and retreat, and maximum depths, which is useful in forecasting and modeling future events. Tropical Storms Katrina and Rita vividly demonstrated that coastal storm surge can be as dangerous as inland flooding caused by rain. For more than 125 years, the USGS has monitored flow in selected streams and rivers across the United States and does so in cooperation with over 850 federal, state and local agencies. State Contacts: If you would like to know more specific information about USGS Tropical Storm Gustav response activities in your area, please contact the appropriate person listed below. Alabama: Athena Clark, 334-395-4141, athclark@usgs.gov Florida: Barry Rosen, 407-803-5508, brosen@usgs.gov Georgia: Ed Martin, 770-903-9166, ehmartin@usgs.gov Louisiana: Charles Demas, 225-298-5481 Ext. 3117, crdemas@usgs.gov Mississippi: Michael Runner, 601-832-3043, msrunner@usgs.gov Texas: Robert Joseph, 512-297-4371, rljoseph@usgs.gov
Fay's Heavy Rains Bring Record Flooding to Parts of Drought Stricken North Carolina
OC_Web@usgs.gov (Office of Communications Web Group)The remnants of what was Tropical Storm Fay brought a deluge of water to parts of North Carolina that were parched by a record-breaking drought. Yet scientists watching the rapidly changing water situation find themselves cautioning residents that this drought is far from over. "Despite the currently high streamflows, effects of the drought likely will linger, as ground-water levels have not returned to normal," said Dr. Jerad Bales, director of the U.S. Geological Survey (USGS) North Carolina Water Science Center. "Moreover, the intensity of the storms resulted in rapid runoff, providing little opportunity for the ground-water system to be replenished." On August 26-27, twenty-four hour rainfall totals at 33 of 74 rain gauges operated by the USGS in Mecklenberg County exceeded the 100-year rainfall—50 of those gauges exceeded the 25-year rainfall. (There is a one-percent chance that the 24-hour, 100-year rainfall is any given year.)  Rainfall totals in excess of 10 inches were reported at 7 of the rain gauges in and around the County.  An additional 53 sites reported more than 5 inches for the event. Although this storm brought heavy rain, it is not a record breaker. The July 22-24, 1997 storm brought up to 13.11 inches of rain and resulted in record floods in Mecklenburg County. Remnants of a tropical storm on August 26-28, 1995 also resulted in high rainfall (maximum of 9.37 inches) and flooding in the county. A flood peak of 16.09 feet was reported at Briar Creek above Colony Road (USGS Station Number 0214645022) at 10:00 yesterday, which exceeded the 1995 (15.6 feet) and 1997 (15.4 feet) peaks by about 0.5 feet. The flood elevation on Mallard Creek near Harrisburg exceeded the previous maximum (1995) by 2.1 ft. Twenty-five USGS stream gauges in Mecklenburg, Lincoln, Gaston, Cabarrus, and Union counties have more than 10 years of record.  Historical maximum flood elevations were exceeded at 9 of these 25 sites following Tuesday and Wednesday's storm. Streamflows throughout western and central North Carolina are currently at normal to above normal conditions. Record streamflows for the date were established yesterday across the Piedmont in the South Fork Catawba River, Haw River, Deep River and Eno River. Streamflows across much of the Coastal Plain, however, remain below normal. For example, a new record minimum flow for the date was established yesterday in the Cape Fear River at Chinquapin. Since the storms in the late 1990's, the USGS has worked in cooperation with the City of Charlotte and Mecklenburg County to develop and enhance the Stormwater Services" Flood Information and Notification System (FINS). The FINS network currently consists of 50 stream gauges and 74 rain gauges equipped with data recorders and radio transmitters that send rainfall and streamflow data as rapidly as once per minute directly to county emergency managers. Rainfall and streamflow data also are displayed on the web for view by the public. USGS crews continue to measure streamflow, monitor the FINS network and collect high water marks across western and central North Carolina to document this event. More information about USGS Hydrologic Data Collection is available on the web.
Science that Weathers the Storm: USGS Scientists in the Field Preparing for Gustav
OC_Web@usgs.gov (Office of Communications Web Group)Reporters: Want to accompany USGS scientists as they install mobile gages or storm surge sensors? Contact Brian McCallum at 404-375-2505 or bemccall@usgs.gov. U.S. Geological Survey (USGS) scientists will be installing rapidly-deployable mobile gages and storm-surge sensors to prepare for Tropical Storm Gustav. These temporary devices are installed just hours before an impending storm and provide additional real-time monitoring data in critical areas needed for effective forecasting and emergency response. "We could not accurately forecast river flows and water-levels without the data and support we receive from the USGS," said Dave Reed, Hydrologist-In-Charge of the National Weather Service Lower Mississippi River Forecast Center in Slidell, LA. "When river and tide data are not available, our job of forecasting is much more difficult and typically results in diminished accuracy of those forecasts." A special interactive USGS Water Hazards Map will be available tomorrow, which will provide real-time flooding and storm surge data from Gulf Coast streamgages and temporary devices. This information is imperative to local, State and Federal officials in order to forecast floods and coordinate flood-response activities in the affected area. Track streamflow and water levels in a Google Map interface and and access other USGS Tropical Storm Gustav efforts. Access real-time data from over 7,500 streamgages across the country by visiting the USGS Water Watch Website. Rapidly deployed mobile stations provide special, short-term data in critical areas lacking long-term streamgages. These mobile real-time stations will help emergency needs and improve coastal flood forecasts. They provide up-to-the-minute data that is critical to the National Weather Service and other partners involved in issuing flood warnings and the evacuation of communities. USGS also has a network of rugged, inexpensive water-level and barometric-pressure sensors, called storm-surge sensors, which will be installed right before Gustav hits land. These sensors provide information about storm surge duration, times of surge arrival and retreat, and maximum depths, which is useful in forecasting and modeling future events. Tropical Storms Katrina and Rita vividly demonstrated that coastal storm surge can be as dangerous as inland flooding caused by rain. For more than 125 years, the USGS has monitored flow in selected streams and rivers across the United States and does so in cooperation with over 850 federal, state and local agencies. State Contacts: If you would like to know more specific information about USGS Tropical Storm Gustav response activities in your area, please contact the appropriate person listed below. Alabama: Athena Clark, 334-395-4141, athclark@usgs.gov Florida: Barry Rosen, 407-803-5508, brosen@usgs.gov Georgia: Ed Martin, 770-903-9166, ehmartin@usgs.gov Louisiana: Charles Demas, 225-298-5481 Ext. 3117, crdemas@usgs.gov Mississippi: Michael Runner, 601-832-3043, msrunner@usgs.gov Texas: Robert Joseph, 512-297-4371, rljoseph@usgs.gov
Ancient Bacteria Uses Arsenic to Grow
OC_Web@usgs.gov (Office of Communications Web Group)Scientists have discovered ancient bacteria that rely on arsenic, rather than water, to grow during photosynthesis.  Analysis indicates that this process probably dates back a few billion years.  This discovery adds an important new dimension to the arsenic cycle and highlights a previously unsuspected process that may have been essential for establishing the arsenic cycle on the ancient Earth. Results are published in Science. Scientists sampled two small hot spring-fed ponds on the south-eastern shore of Paoha Island in Mono Lake, CA. The springs were termed "green" and "red" based on the colors of the microbiological films in the pools that were studied. Samples from these springs oxidized the highly toxic Arsenic(III) to the less toxic and less mobile  Arsenic(V) by light-dependent  photosynthetic reaction that occurred in the absence of oxygen. The scientists also isolated a photosynthetic bacterium that demonstrated As(III)-dependent growth under anoxic conditions. NASA's Exobiology Program helped to fund the research along with the USGS. Collaborating colleagues in the diverse, team-oriented aspects of the experimental work were from Duquesne University (Prof. J.F. Stolz; Pittsburgh, PA) University of Georgia (Prof. J.T. Hollibaugh and Dr. J.Fisher); Athens, GA), Southern Illinois University (Prof. M. Madigan, and Dr. M.Asao), the USGS in Menlo Park, CA (Dr. R.S. Oremland, Dr. T.R. Kulp, S.E. Hoeft, and L.G. Miller) and the USGS Water Science Center in Maine (C.W. Culbertson).  Arsenic is a chemical element and is a natural constituent of the Earth's crust. It occurs naturally in rocks, soil, water, air, plants and animals. When in the natural environment, arsenic usually binds to other molecules, such as those found in soils, and does not tend to travel very far. The average concentration of arsenic in soils in the United States varies considerably. Arsenic can be released into the environment through natural processes such as volcanic activity, erosion of rocks and forest fires. Human actions, such as agricultural practices, mining, smelting and combustion of fossil fuels also contribute to arsenic releases in the environment.
Strategy to Assess the Nation's Ground-Water Availability
OC_Web@usgs.gov (Office of Communications Web Group)Scientists proposed a strategy to study the Nation's ground-water supply as part of the Federal government's effort to help address the Nation's increasing competition for water. Declines in ground-water levels have led to concerns about the future availability of ground water, which provides half the country's drinking water and is essential to the vitality of agriculture and industry, as well as to the health of rivers, wetlands, and estuaries throughout the country.  The report, "Ground-Water Availability in the United States" examines what is known about the Nation's ground-water availability and outlines a strategy for future national and regional studies that would provide information to help state and local agencies make informed water-availability decisions. View the report on-line at http://pubs.usgs.gov/circ/1323/. "An assessment of ground-water availability is critical for state and local agencies to make decisions about important issues such as drinking water, industrial and energy production, and agricultural uses," says William Alley, USGS Office of Ground Water Chief. The approach outlined in the report is designed to provide useful regional information for State and local agencies who manage ground-water resources, while providing the building blocks for a national assessment. The report places the regional studies by the USGS Ground-Water Resources Program as a long-term effort to understand ground-water availability in major aquifers across the Nation. The report contains information about 30 regional principal aquifers and five case studies to illustrate the diversity of water-availability issues. The report is written for a wide audience interested or involved in the management, protection, and sustainable use of the Nation's water resources.  Ground water, a hidden resource found below the surface of the Earth, is among the Nation's most important natural resources. Extensive use of ground-water resources and other effects of pumping has led to concerns about the future availability of ground water to meet domestic, agricultural, industrial, and environmental needs. Determining ground-water availability is a complex process. Issues affecting ground-water vary from location to location and commonly require analysis in the context of ground-water flow systems to achieve a meaningful perspective. Even if water resources are abundant regionally, heavy water use in centralized areas can create local stresses. As water-related problems evolve in complex ways, an up-to-date and comprehensive evaluation of ground-water resources that builds on the foundation of previous studies is needed to meet society's ever-changing water demands. This report is an outgrowth of a pilot study, National Assessment of Water Avail­ability and Use, that began in 2005 at the request of Congress. The report also builds on regional ground-water availability studies recently undertaken as part of the USGS Ground-Water Resources Program. The approach to national ground-water assessment is a key element of the water census of the United States, which has been proposed as part of the proposed Federal science strategy to meet nationwide water chal­lenges by the National Science and Technology Council Subcommittee on Water Availability and Quality.
Don't be Left Out! Three Months to ShakeOut
OC_Web@usgs.gov (Office of Communications Web Group)Thousands Join Each Day, You Can Too Three months from today, at 10 a.m. on November 13, millions of southern Californians will drop to the ground, take cover under a table or desk, and hold on. An earthquake prediction? No. But it is certain that the Great Southern California ShakeOut is on track to being the largest earthquake drill in United States history. As of today, over 1.7 million people have been registered at www.ShakeOut.org, with over 200 schools and districts leading the effort by scheduling their annual earthquake drills on November 13. The goal is to involve at least 5 million people. "Something remarkable is happening-people are seeing this as an unprecedented opportunity to really get themselves, their organizations, and their communities prepared," said Mark Benthien, director for Outreach at the Southern California Earthquake Center at USC. Many participants will go even further with full-scale drills of how they will speed their recovery in a massive earthquake. "Every day we hear from schools, businesses, and many others about what they are planning and how they are excited to be a part of the ShakeOut, and to encourage others to participate." Why? An enormous earthquake is in Southern California's future, and the ShakeOut Drill is a chance to practice so residents are ready when it happens. ShakeOut is based on a potential magnitude 7.8 earthquake on the southern San Andreas Fault-approximately 5,000 times larger than the magnitude 5.4 earthquake that shook southern California on July 29. Dr. Lucy Jones of the U.S. Geological Survey has led a group of over 300 scientists, engineers, and others to study the likely consequences of this potential earthquake in great detail. The result is the ShakeOut Earthquake Scenario (urbanearth.usgs.gov), which is also the basis of this year's statewide emergency response exercise, Golden Guardian 2008 (www.ohs.ca.gov). "All this is coming together in a way that has never happened before," said Dr. Jones. "What's really rewarding as a scientist is to see how the scientific foundation provided by the ShakeOut Scenario seems to be inspiring real preparedness actions throughout the region. This is important because it's what we do now, before a big earthquake, that will determine what our lives will be like after."  Detailed instructions for how to participate and get prepared for earthquakes are on the ShakeOut website. Here are key aspects of the ShakeOut: ShakeOut is organized by the Earthquake Country Alliance (ECA), a partnership of earthquake professionals, emergency responders, business leaders, and community activists. The group has been planning the ShakeOut since 2006.  Major organizations include the USGS, Southern California Earthquake Center, California Office of Emergency Services, City of Los Angeles, Art Center College of Design, State Farm, and California Institute of Technology. To be able to reach communities throughout southern California, the ECA is launching "Regional Associate" groups in each county: The San Bernardino County group has its initial meeting today and is co-chaired by County Supervisor Brad Mitzenfelt and ESRI President Jack Dangermond. The Los Angeles Group will meet on August 21 and is led by County Fire Chief P. Michael Freeman.  Riverside County Associates are led by County Emergency Manager Peter Lent and Congresswoman Mary Bono. San Diego County Associates are led by County Emergency Manager Ron Lane and two Fire Chiefs.  Orange County Associates are led by County Emergency Manager Donna Boston. Associate groups for other counties are in formation. Sponsors of the Great Southern California ShakeOut activities include USGS, National Science Foundation, FEMA, California Office of Emergency Services, City of Los Angeles, State Farm, California Earthquake Authority, Kaiser Foundation Health Plan, Tyco Electronics, Provention Consortium, Dewberry, Degenkolb, Network for Earthquake Engineering Simulation, Institute for Business & Home Safety, ABC7, and others soon to be announced. Organizations wishing to support ShakeOut activities can learn more at www.ShakeOut.org/sponsors. In addition to the ShakeOut drill, the City of Los Angeles and the Earthquakes and Megacities Initiative are hosting an International Earthquake Conference November 12-14, bringing together over 45 international experts to discuss policy, planning, and preparedness with U.S. counterparts. Online registration is available, and early registration incentives are available through the end of August. More information can be found at www.iec.lacity.org. On Friday, November 14, Art Center College of Design will present the "Get Ready Rally" at the new Nokia LA Live in downtown Los Angeles to engage the public in earthquake preparedness. All southern Californians are invited to celebrate the success of the Drill and share their experiences. There will be food, entertainment, and vendors. To participate, go to www.ShakeOut.org and pledge your family, school, business, or organization's participation in the drill. Registered participants will receive information on how to plan their drill, encourage others to participate, and improve their earthquake preparedness. It all begins with registering, which is free and open to everyone.

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