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USGS2000

US GeoData Digital Elevation Models

Digital elevation model (DEM) data are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The U.S. Geological Survey (USGS) produces five primary types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM.

Fact Sheet↗
USGS2002

Water-quality trends in suburban Houston, Texas, 1954-97, as indicated by sediment cores from Lake Houston

Water-quality trends were assessed in Lake Houston using age-dated sediment cores. Sediments deposited in the lake contain a partial chemical signature of human activities in the watershed. Over time, a water-quality history is recorded in the bottom sediments. Although the sediments in Lake Houston are clean compared to sediment-quality guidelines, increasing concentrations of mercury, zinc, and polycyclic aromatic hydrocarbons (PAHs) during the past several decades are evidence of the increasing human effect on water quality. The positive effects of regulation are indicated by decreases in concentrations of lead and DDT.

Texas↗
USGS1997

Organochlorine compounds and trace elements in streambed sediment and fish tissue, South Platte River Basin; Colorado, Nebraska, and Wyoming

Concentration data for organochlorine compounds and trace elements in streambed sediment and fish tissue collected throughout the South Platte River Basin as part of the U.S. Geological Survey's National WaterQuality Assessment (NAWQA) Program were evaluated to determine the following: (1) which organochlorine compounds and trace elements occurred most frequently, (2) whether detection frequencies and concentrations differed among land uses, (3) how measured concentrations related to established standards and guidelines, and (4) whether there was any relation between concentrations in streambed sediment and fish tissue. Streambed sediment and fish tissue were collected at 23 sites, which were selected on the basis of physiography, geology, and land-use characteristics.

Fact Sheet↗
USGS2000

Ordering procedures for photographic enlargement products--NAPP, NHAP, and custom

Established in 1987, the National Aerial Photography Program (NAPP) collects aerial photographs of the 48 conterminous States on a 5-year cycle. Copies of NAPP images are available in black-and-white and (or) color- Figure 1. NAPP paper-print sizes and their corresponding scales for standard enlargements.* infrared film at 1 :40,000 scale. Figure 1 shows NAPP paper-print sizes and their corresponding scales for standard enlargements.

Fact Sheet↗
USGS1997

Water quality of selected streams in Montgomery County, Indiana, 1996

The USGS sampled streams in Montgomery County as part of a study done in cooperation with the Montgomery County Commissioners. The sampling program was designed by the Montgomery County Sanitarian and USGS hydrologists. The program focused on assessing general surface-water quality throughout the county and also targeted some specific areas of interest to county officials.

Indiana↗