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 digitized contours of unconsolidated-sediment thickness (depth to bedrock).
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. It also was used as an input source (along with datasets of bedrock-outcrop polygons and point data) for the automated generation of a surface of unconsolidated-sediment thickness, also contoured for use in 1:50,000 maps.
Unconsolidated-sediment thickness data from well logs (see "Lineage" section) were manually plotted and contoured onto mylar overlays of 45 paper USGS 7.5-minute topographic series quadrangle maps that encompass the Colorado Front Range Infrastructure Resources Project area. The mylar overlays were scanned into Tagged Image File Format (TIFF) image files that were then converted into Arc/INFO raster datasets known as grids. The grids were converted into vector datasets known as coverages in Arc/INFO-specific terminology. Arc item "CONTOUR" was added to the arc attribute tables of the coverages and manually attributed in Arcedit, using the original manuscript mylars for references. The coverages were then projected into a common map coordinate system and edgematched. The northern and eastern areas of each coverage were edgematched when necessary: the linework of the northern edge of a coverage was adjusted to fit the linework of the southern edge of a coverage adjacent to the north; the linework of the eastern edge of a coverage was adjusted to fit the linework of the western edge of a coverage adjacent to the east. The linework from each coverage was appended into a single coverage in which dangling vectors less than 12.192 meters long were removed and in which vector vertices and nodes within 1.2192 meters of each other were merged. The coverage was built with line topology. Arc item "CONTOUR_M" was added to the arc attribute table of the coverage and was calculated as the metric equivalent of item "CONTOUR." Linework extends beyond the southern edge of the study area for consistency with previous work in that area (Robson, 1996). 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, 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, 2000b, 2000c, 2000d).
Horizontal_Positional_Accuracy_Explanation The horizontal positional accuracy value pertains to accuracy of transcription from manuscript to digital format. Digitized linework should fall within 0.02 inch of original 1:24,000-scale mylars. At a scale of 1:24,000, 0.02 inches equals 12.2 meters.
No tests were performed to verify the Horizontal Positional Accuracy Value.
Maps of unconsolidated-sediment thickness were prepared at 1:24,000 by hand-contouring data with 10- and 20-foot-contour intervals. These maps were produced directly from data and for the purposes of this study are considered to be first-order maps with a vertical accuracy of about 10 feet or 3 meters.
No tests were performed to verify the Horizontal 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
Unconsolidated-sediment thickness, in feet.
U.S. Geological Survey
Unconsolidated-sediment thickness, in meters.
U.S. Geological Survey
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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.
Sediment thickness contours geographic features
Sediment thickness 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