The U.S. Geological Survey developed this dataset as part of the Colorado Front Range Infrastructure Resources Project (FRIRP). One goal of the FRIRP was to provide information on the availability of those hydrogeologic resources that are either critical to maintaining infrastructure along the northern Front Range or that may become less available because of urban expansion in the northern Front Range. This dataset extends from the Boulder-Jefferson County line on the south, to the middle of Larimer and Weld Counties on the North. On the west, this dataset is bounded by the approximate mountain front of the Front Range of the Rocky Mountains; on the east, by an arbitrary north-south line extending through a point about 6.5 kilometers east of Greeley. This digital geospatial dataset consists of bedrock-surface-elevation contours that were generated with a Geographic Information System (GIS).
This dataset was created by the U.S. Geological Survey (USGS) in the development of the USGS Front Range Infrastructure Resources Project. This dataset was used in the creation of 1:50,000-scale hydrogeologic contour maps.
Using Arc/INFO software, USGS 7.5-minute Digital Elevation Models (DEMs) that encompass the study area were converted to raster surface formats (grids, in Arc/INFO terminology). They were mosaicked into a single continuous surface with the Arc/INFO GRID function, MERGE, and projected into an appropriate coordinate system with the command, PROJECT. To prevent the final bedrock-surface elevations contours from appearing too convoluted and implying more detail than is supportable by the unconsolidated-sediment-thickness dataset, the resulting grid was then smoothed using a circular averaging filter with a radius of 9 grid cells (180 meters), using the grid command, FOCALMEAN. Line datasets (coverages, in Arc/INFO terminology) of unconsolidated-sediment-thickness contours and bedrock-outcrop outlines (see Cross_Reference section) were converted to a grid with the same cell size as the DEM-derived data (approximate 30-meter spacing between data points) using the GRID command, TOPOGRID, which was set to run for 45 iterations with the primary z-value input as contour data, and no drainage enforcement. The unconsolidated-sediment-thickness grid was subtracted from the land-surface-elevation grid to produce a grid of bedrock-surface elevation. Using the bedrock-surface-elevation grid, the software generated the contour coverage at an interval of 20 feet. Manual editing corrected contours that were not correctly interpolated, as determined by consultation with the project hydrologist; for example, contours that formed closed polygons with perimeters less than 1,000 meters were removed. This coverage was clipped to fit the study-area boundary. The final coverage is intended to be used as one thematic layer in maps to be published at a scale of 1:50,000. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.
publication date
This dataset should not be used at a scale larger than 1:50,000.
PO BOX 25046 MS 415
Chain-node topology, as verified by ESRI Arc/INFO v. 7.x BUILD, is present.
Information concerning completeness that is not contained in the Supplemental_Information element can be found in Robson and others (2000a, 200b, 2000c, 2000d).
Maps of unconsolidated-sediment-thickness contours were prepared at 1:24,000 scale by hand-contouring data with 10- and 20-foot-contour intervals. These maps were produced directly from data and are considered to be first-order maps with a vertical accuracy of about 10 feet. These maps were then digitized for use in the GIS. Digital elevation models and the equivalent topographic quadrangle maps with 10- or 20-foot contour intervals are also considered to be first-order data with a vertical accuracy of 5 or 10 feet. Bedrock-surface elevation was computed as the difference between land-surface elevation and unconsolidated-sediment thickness. Bedrock-surface-elevation is considered to be a second-order dataset because it was computed from two first-order datasets. The contours likely have a vertical accuracy between 10 and 15 feet or about 4 meters.
No tests were performed to verify the Vertical Positional Accuracy Value.
lithologic and water-level data
lithologic data
lithologic data
lithologic data
lithologic data
lithologic data
lithologic data
lithologic data
water-level data
lithologic data
water-level data
lithologic data
lithologic data
lithologic data
lithologic and water-level data
lithologic and water-level data
water-level data
water-level data
lithologic data
water-level data
water-level data
water-level data
lithologic data
water-level data
lithologic data
water-level data
lithologic data
lithologic data
lithologic data
lithologic and water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
unknown
unknown
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
lithologic data
water-level data
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
water-level data
lithologic data
lithologic data
unknown
lithologic data
lithologic data
lithologic data
lithologic data
lithologic data
lithologic data
lithologic data
lithologic and water-level data
lithologic data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
water-level data
lithologic data
water-level data
lithologic data
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
lithologic and water-level data
See Supplemental Information.
Internal feature number.
ESRI
Feature geometry.
ESRI
Internal node number for the beginning of an arc (from-node).
ESRI
Internal node number for the end of an arc (to-node).
ESRI
Internal node number for the left polygon.
ESRI
Internal node number for the right polygon.
ESRI
Length of feature in internal units.
ESRI
Internal feature number.
ESRI
User-defined feature number.
ESRI
Bedrock-surface elevation, in feet above sea level.
U.S. Geological Survey
507 National Center
Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
bedrock-surface-elevation contours geographic features
bedrock-surface-elevation contours geographic features
ArcIMS Image Map Service
A web-based interactive mapping system that accesses an ArcIMS Map Service running on certmapper.cr.usgs.gov.
Full coverage
Full coverage
Full coverage
507 National Center