The National Geodetic Survey (NGS) develops and maintains a national coordinate system, which provides the foundation for transportation, navigation, land record systems, mapping and charting efforts, defense operations, and a multitude of scientific and engineering applications. NGS products, services, and data support maritime navigation, aviation safety, hurricane evacuation routes, climate change activities, ocean observing, and more.
Two of the world's premier research aircraft, the renowned NOAA WP-3D Orions, participate in a wide variety of national and international meteorological, oceanographic, and environmental research programs in addition to their widely known use in hurricane research and reconnaissance.
In fiscal year 2011, NGS Gravity for the Redefinition of the American Vertical Datum (GRAV-D) airborne survey efforts focused on gravity data collection in Alaska, with a large portion of the over 600,000 square kilometers completed flown aboard one of the two NOAA Hurricane Hunter WP-3D Orion aircrafts. NGS’s GRAV-D Project will allow surveyors and scientists to use Global Navigation Satellite System technology, including the Global Positioning System, to determine more precise and accurate elevations than currently possible, in less time and with less effort. The current vertical datum is anchored by survey monuments whose expected vertical accuracy was never fully realized and whose current accuracy is difficult to maintain, particularly in regions where dynamic processes like subsidence (land sinking) and earthquakes cause monuments to move. Although our vertical datum has a high internal consistency (precision) and performs well in local surveys, recent satellite measurements reveal systematic biases in absolute elevations relative to sea level of an average of 50 centimeters in the continental U.S., with over one meter of coast-to-coast tilt and at least two meters in those few parts of Alaska which contain any survey monuments. However, when GRAV-D is successfully completed and the new elevation system is accessed using the NGS Online Positioning User Service (OPUS) software, these elevation errors will be reduced to just under two centimeters in non-mountainous regions. Surveyors will continue to perform high-accuracy local surveys, but anchored to more accurate benchmark values.
This improved vertical reference system is a key component of the enhanced geospatial framework required for success in achieving NOAA’s strategic priorities. The system is of particular importance for community resilience, helping to determine where water flows in order to make accurate inundation models and assessments as well as better management and planning decisions based on accurate elevations.
Aerial survey cameras aboard NOAA's newest aircraft, the NOAA King Air 350ER, were used to determine the extent of Red River flooding and to validate flood models.
During fiscal year 2011, NGS provided vital emergency response imagery. In April, NGS’s Remote Sensing Division and NOAA’s Office of Marine and Aviation Operations (OMAO) deployed to North Dakota to collect aerial imagery of areas affected by the Red River flooding. With more than 30 hours of flight time, imagery data were collected in coordination with NOAA’s North Central River Forecast Center to validate their flood models. Later in April and in early May, NGS and OMAO deployed to the Birmingham and Tuscaloosa, Alabama, areas for aerial mapping of the long swath of catastrophic tornado damage in the southeast. Later in May, NGS deployed to Joplin, Missouri, to collect nearly 1,500 disaster response images of the catastrophic tornado damage that took place in that area. And in August, in the aftermath of Hurricane Irene, NGS collected imagery and topographic LiDAR data along the Atlantic seaboard from Beaufort, North Carolina, to Cape Henry, Virginia. This imagery is also available on a newly launched mobile website that makes it possible for emergency responders to access emergency response imagery while in the field.
These interagency projects were conducted and coordinated by personnel from NOAA’s National Weather Service, OMAO, and the National Ocean Service, as well as the U.S. Army Corps of Engineers, the Federal Emergency Management Agency, State of Alabama authorities, and others.
During fiscal year 2011, the National Geodetic Survey (NGS) completed a full reprocessing of Global Navigation Satellite System (GNSS) data collected at stations in the global network of the International GNSS Service and in the regional network of the U.S. Continuously Operating Reference Stations. The focus of the effort was development of a new version of the North America Datum of 1983 (NAD 83)—the horizontal datum for the United States—in the framework of the International Terrestrial Reference Frame of 2008 (ITRF). The ITRF is the global reference frame used for latitude, longitude, and height positions.
NGS is charged with providing the underlying framework for all positioning activities in the United States, and NAD 83 is a key part of the infrastructure designed for this purpose. This new realization of NAD 83 is the result of a series of data analysis improvements and is expected to provide users with an overall improvement in the accuracy of their precise positioning activities, such as sea level change monitoring, precision agriculture, and surveying.
The first edition of NOAA’s Vertical Datum Transformation (VDatum) tool is now available for the entire contiguous United States. This online tool enables users to seamlessly transform geospatial data based on different vertical reference systems into one uniform surface, or “datum.” Transforming data to a single vertical datum removes the most serious impediments to data sharing and is necessary to harmonize the differences between the vertical reference systems of land- and water-based spatial data.
VDatum is a free software tool jointly developed by NOAA’s National Geodetic Survey, Office of Coast Survey, and Center for Operational Oceanographic Products and Services. It was first introduced to support a seamless bathymetric-topographic digital elevation model (DEM) for Florida’s Tampa Bay region. The DEM that resulted from the VDatum Demonstration Project has not only solved the problem of inconsistency among diverse datasets that causes difficulty in mapping coastal regions, but also provides standard geospatial data for multiple applications, such as inundation modeling, monitoring sea-level change impacts, coastal management, and more.
Accurate datums are important for preventing mishaps to infrastructure projects such as bridges.
As NGS moves closer to replacing the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88), NGS is interacting closely with agencies that use the datums to assist in the transition. Much of the interaction with agencies is being conducted through NGS pilot projects. The first pilot project, with the Federal Emergency Management Agency, was conducted in North Carolina in cooperation with the North Carolina Geodetic Survey. The eight-month project was designed to improve understanding the impact of the new datums on floodplain mapping data and products and to begin a dialogue on policies and procedures requiring updating.
Accurate, reliable, and up-to-date datums are essential for a wide range of activities, including managing construction and infrastructure projects such as bridges, dams, and levees; alerting emergency planners to changes in elevation over storm evacuation routes that are slowly sinking and are susceptible to inundation; mapping floodplains to produce accurate flood zone maps and determine flood insurance rates; precisely controlling equipment used in agriculture and road construction; monitoring sea-level changes; and managing ecosystem restoration projects, to name just a few.