Hypsography/Elevation
Hypsography or elevation data refers to a representation of spatially referenced vertical positions above or below a datum surface. This type of geospatial data may be represented by elevation values separated by a consistent grid spacing in the form of the United States Geological Survey's (USGS) Digital Elevation Models also known as DEMs, or may be derived from Light Detection and Ranging technology known as LiDAR or by Interferometric Synthetic Aperture Radar known as ifSAR. Digital representations of contour information known as hypsography represent lines of vertical elevation values above or below a datum surface. Hypsography or elevation data is a less advanced vector line and point representation of the terrain, such as a contour map.
Elevation data can also be used to perform applications ranging from line-of-sight calculations, to transportation planning, and water shed management. Elevation data is often combined with other digital data themes for modeling and mapping applications. The standard product that the USGS produces and the representation adopted as the Montana Spatial Data Infrastructure elevation theme is the DEM collected in 10 or 30 meter grid spacing with coverage in 7.5- x 7.5-minute blocks. Each USGS DEM provides the same coverage as a standard USGS 7.5-minute map quadrangle.
Additionally seamless and multi-resolution digital elevation data sets are now becoming available and the USGS has compiled these into a single coverage called the National Elevation Dataset or NED. The USGS NED has been developed by merging the highest-resolution, best quality elevation data available across the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale seamless DEM data for the conterminous U.S. NED has a consistent projection (Geographic), resolution (1 arc second), and elevation units (meters). The horizontal datum is NAD83 and the vertical datum is NAD88. NED is a living dataset that is updated bimonthly to incorporate the "best available" elevation data. Source data for the NED varies. As of October 2010 the entire state of Montana is covered with true 1/3 arc second (about 10-meter) data.
Stewardship of the Elevation Framework theme will focus on producing higher resolution data, taking advantage of opportunities to cooperate in the production and maintenance of elevation data through new and improved technology and providing access to this data via data portals and links to state and national data clearinghouses. Stewardship of this theme is highly dependent on a close working relationship with the USGS (maintainer) and other interested agencies (producers / users) of elevation data. Much of the state's elevation needs will be met by establishing state priority areas and using our established federal liaison network to forward requirements for inclusion in annual federal production and maintenance programs. Secondly we will establish links to the Montana Data Portal, the Center for LiDAR Information C coordination and Knowledge (CLICK) the USGS Seamless Data Site, and the Geospatial One-Stop data portal that provide resources and information regarding future elevation data requirements and data production that can be easily accessed and incorporated into Montana's state data holdings.
Goals
Having obtained our 2010 goal of complete true 10-meter elevation models our goal for 2011 is to seek out opportunities for high resolution data collection over specific project areas, support a federal elevation inventory and needs assessment and investigate elevation services that support local, state and federal interest.
Status of Framework
All of Montana is now available as 1/3-arc second (about 10-meter) National Elevation Dataset (NED).
The status of know higher resolution elevation data such as LiDAR can be found at the Center for LiDAR Information Coordination and Knowledge web site: http://lidar.cr.usgs.gov/
USGS NED tools and services can be located at: http://seamless.usgs.gov/ned13.php
Stewardship Contact Information
Theme Steward
U.S. Geological Survey
Framework Theme Lead
Lance S. Clampitt
USGS Geospatial Liaison for Montana
NSDI Partnership Office
USGS, NRMSC
Fax: 406-994-6919
Phone: 406-994-6556
E-mail: lsclampitt@usgs.govlsclampitt@usgs.gov
Theme Lead's Corner
The USGS has taken the lead in producing and maintaining elevation data for the nation. In Montana, elevation data supports numerous applications from flood plain and view shed modeling to three dimensional hill shade representations of this great state. The elevation framework data theme is unique as a majority of the data has been produced by the USGS and much of it built through cooperative partnerships with users like you. As the USGS Geospatial Liaison to Montana I encourage your continued collaboration in improving this geospatial data resource.
~ Lance S. Clampitt,
Hypsography/Elevation Framework Theme Lead
