FLORIDA GEOGRAPHIC DATA LIBRARY DOCUMENTATION
VERSION 2005

TITLE: USGS 1:250,000 DIGITAL ELEVATION MODEL

Geodataset Name:     USGSDEM
Geodataset Type:     Grid
Geodataset Feature:  Surface

GENERAL DESCRIPTION

This dataset contains a Digital Elevation Model (DEM). The USGSDEM is an ARC/INFO grid that consists of 92 meter cells whose values represent elevation relative to sea level. These floating point values enable us to display a continuous surface of elevation, as opposed to topography which is broken into intervals.

RESOLUTION:                     90 Meter

GRID TYPE:                      Integer

DATA SOURCE:                    UNITED STATES GEOLOGICAL SURVEY

SCALE:                          1:250,000

DATE OF AUTOMATION OR SOURCE:   Source: 1972, Automated 1984

GEODATASET EXTENT:              State of Florida

FGDL QUALITY ASSURANCE STATUS:

-Converted from floating point to integer type using truncation.
 This was done to make the GRID smaller.

USER NOTES:

The cell values for this grid represent elevation in meters.

DEM's may be used to do the following types of analysis: hydrologic analysis including flow direction, flow accumulation, and watershed delineation; and determination of slope and aspect, and analytical hillshading.

REFERENCES:

Jenson, S.K. and J.O. Domingue. 1988. Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis. Photogrammetric Engineering and Remote Sensing. 54(11) 1593-1600.

Philip, G.M. and D.F. Watson. 1982. A Precise Method for Determining Contoured Surfaces. Australian Petroleum Exploration Association Journal 22: 205-212.

http://rmmcweb.cr.usgs.gov/elevation/dpi_dem.html

ARCDoc Online Help for ArcInfo.

MAP PROJECTION PARAMETERS:

Projection                         ALBERS
Units                              METERS
Datum                              HPGN
Spheroid                           GRS1980
1st standard parallel              24   0  0.000
2nd standard parallel              31  30  0.000
central meridian                  -84   0  0.000
latitude of projection's origin    24   0  0.000
false easting (meters)             400000.00000
false northing (meters)            0.00000

DATA SOURCE CONTACT(S):

Name:                UNITED STATES GEOLOGICAL SURVEY
Abbr. name:          USGS
Address:             USGS Mapping Applications Center
                     National Cartographic Info Center
                     507 National Center
                     Reston, VA 22092
Phone:               (703) 860-6045
Fax:                 (703) 648-4165
Web site:            http://www.usgs.gov
		     http://mapping.usgs.gov/mac/
E-mail:              MACWEBMASTER@USGS.GOV
Contact Person:      They will route your message to the person best
                     qualified to respond.

* Please use the email address as the primary method of contacting GeoPlan. The phone number can be used as a secondary form of contact. Thank you.

FGDL CONTACT:

Name:                   FLORIDA GEOGRAPHIC DATA LIBRARY
Abbr. Name:             FGDL
Address:                Florida Geographic Data Library
                        431 Architecture Building
                        PO Box 115706
                        Gainesville, FL  32611-5706
Web site:               http://www.fgdl.org

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