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 know as DEMs, or may be derived from Light Detection and Ranging technology know 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 data is usually represented by vector lines and points representing contours and spot elevations.

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's Elevation theme is the DEM collected in 10 or 30 meter grid spacings. 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. While 1/3 arc second (about 10-meter) data is available for the entire state of Montana, approximately 40% of it was built with 30 meter source DEMs which have been over sampled to meet the needs of a seamless dataset.

Stewardship of the Hypsography 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 Coordination and Knowledge (CLICK) the USGS Seamless Data Site, and the Geospatial One-Stop data portal which 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

A major goal for this framework theme is to complete true 10-meter elevation models for the remainder of the state. In doing so we will focus our efforts over the areas impacted most by natural and manmade disturbances, low lying lands susceptible to flooding and the northern tier quadrangles along the US / Canadian boarder. We will also improve existing elevation data with that of high resolution elevation data through partnership opportunities with local, state and federal interest.

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Status of Framework

All of Montana is now available as 1/3-arc second (about 10-meter) National Elevation Dataset (NED). However the source data for NED varies. The areas shown in blue on the status graphic are areas where 1/3-arc second data has been produced using over sampled 30-meter data. True 10-meter data does not exist over these areas. For updated status of this dataset visit http://seamless.usgs.gov/ click on View & Download data and turn on layer extent using the right side bar of the viewer.

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://gisdata.usgs.gov/Lidar/.

View a map featuring the USGS 10-Meter DEM Availability!

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Stewardship Contact Information

Theme Steward

U.S. Geological Survey (USGS)
Northern Rocky Mountain Science Center

Framework Theme Lead

Lance S. Clampitt
U.S. Geological Survey (USGS) Geospatial Liaison for Montana
NSDI Partnership Office
USGS, NOROCK
Fax: 406-994-6919
Phone: 406-994-6556
E-mail: lsclampitt@usgs.govlsclampitt@usgs.gov