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GIS Database Project

The Western Geographic Science Center (WGSC) of the USGS created and maintains a geographic information system (GIS) project for the San Francisquito Creek. The GIS project brings together geographic information describing the creek and watershed, depicts existing conditions, provides information and educational material to the public, and supplies stakeholders with spatial information needed to make management decisions. Data prepared for the GIS project have enabled the WGSC to respond to requests for printed maps on a variety of themes.

The GIS project includes a number of different data layers containing high-quality digital maps of geographic and geologic information. The GIS project provides a way to codify and distribute geospatial data (hydrology, geology, soils, political boundaries, land use, remotely sensed data, etc.) that were gathered, processed, and disseminated for the creek. While the GIS project is by no means comprehensive, it does provide an introduction to using geospatial data to frame and explicate natural resource questions.

The basic elements of the GIS project are the standard USGS datasets at 1:24,000 scale. The four USGS digital cartographic products are as follows:

  1. Digital Raster Graphic (DRG) -- A scanned version of the USGS 7.5-minute topographic map.
  2. Digital Line Graph (DLG) -- Cartographic data in vector format (geographic data in points, lines, and polygons).
  3. Digital Elevation Model (DEM) -- Cartographic/geographic data of elevations in xyz coordinates (view data in 3-D).
  4. Digital Orthophoto Quadrangle (DOQ) -- A digital, uniform-scale image created from aerial photos (a photographic map).


DRG icon.


DLG icon.


DEM icon.


DOQ icon.

These four data productes are the basic building blocks for the geospatial database. Often the raw-data format available from the USGS database is not the most useful format for public dissemination. In most cases, these data are mosaicked and reprojected to one standard projection. The modified files are more convenient for viewing and analyzing information for the area of interest. The DLGs contain a wide variety of information depicting geographic features (for example, hypsography, hydrography, boundaries, roads, utility lines, etc). The 10-meter DEMs supply elevation, slope, and drainage information. The DRGs and DOQs are used as base maps for additional layers of information to be added to the database.

In addition to the standard USGS geospatial products, we included GIS layers from other gorups within USGS and outside agencies. The San Andreas Fault system, non-debris-flow landslide deposits, distribution of Earth flows, and geology data are from the USGS Geologic Discipline. The 1990 census data are used for reference purposes. Land cover data are from the National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center. The watershed boundaries are from the Santa Clara Valley Water District. Other data layers include town boundaries from the Regional Water Quality Control Board and parks from the Midpeninsula Regional Open Space District.

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Study Area
GIS Project
Digital Data
U.S. Department of the Interior || U.S. Geological Survey || National Mapping Information || Western Regional Geography
Home Page. First Gov, your first click to the US Government. URL: http://geography.wr.usgs.gov/sfcreek/gis_database.html
Designer and Maintainer: Connie Hoong, choong@usgs.gov
Webmaster: Gary Sullivan, gsullivan@usgs.gov
Last Modified: Wednesday, 15-Jan-2003 13:53:59 EST (cmh)
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