Slope of Georgia


Identification_Information
Data_Quality_Information
Spatial_Data_Organization_Information
Spatial_Reference_Information
Entity_and_Attribute_Information
Distribution_Information
Metadata_Reference_Information



Identification Information
Section Index

Citation:
Citation Information:
Originator: Musser, Jonathan W.
Publication Date: 1997
Title: Slope of Georgia
Publication Information:
Publication Place: Atlanta, GA
Publisher: U.S. Geological Survey
Online Linkage: http://csat.gatech.edu/csat/statewide/statewide.html
Description:
Abstract:
Digital Elevation Model (DEM) is the terminology adopted by the USGS to describe terrain elevation data sets in a digital
raster form. The standard DEM consists of a regular array of
elevations cast on a designated coordinate projection system.
The DEM data are stored as a series of profiles in which the
regular whole number intervals. The normal orientation of
data is by columns and rows. Each column contains a series of
elevations ordered from south to north with the order of the
columns from west to east. The DEM is formatted as one
ASCII header record (A-record), followed by a series of profile
records (B-records) each of which include a short B-record
header followed by a series of ASCII integer elevations per each
profile. The last physical record of the DEM is an accuracy
record (C-record).
A 1-degree DEM (3- by 3-arc second data spacing) provides coverage
in 1- by 1-degree blocks. Two of these products
(three in some regions of Alaska) provide the same coverage
as a standard USGS 1- by 2-degree quadrangle. The basic
elevation model is produced by or for the Defense Mapping
Agency (DMA), but is distributed by the USGS in the DEM data
record format. Coverage is for the United States.
This is Slope which is a direct derivative of the DEM, with
the documentation information for the DEM applying directly.
Purpose:
Slope can be used for earth science analyses such as rainfall runoff modeling, determining erosion potential, or finding
environmentally sensitive areas.
Supplemental Information:
Procedures Used- 1. The data was acquired from NMD over the internet with ftp as
1- by 1-degree blocks.
2. The DEM files were processed with Arc/Infos demlattice to produce
elevation grids.
3. The elevation grids were merged together to form one large merged grid.
4. The merged grid was projected into an albers equal-area projection.
5. Slope was computed with a percent value for amount of rise versus
amount of horizontal distance travelled.
6. A mask grid was created using the 1:100,000 state boundary and the same
cell size and orientation as the albers grid.
7. The mask grid was used to clip the slope grid to the state boundary.
8. A coastline coverage from the NOAA 1:70,000 coastline was used to create
a mask grid of the ocean and inland waterways around the coastal islands.
9. The final slope grid was created by using this mask grid to clip out
the coastline and islands.
Reviews Applied -
1. Data checked for complete coverage, no missing data.
2. Visual inspection based on known ground surface elevation features.
3. Colleague review November 3, 1997 by Jack Alhadeff and Diane Burgoon.
Digital data was reviewed with respect to positional accuracy, contextual
accuracy, attribute accuracy, topological consistency, and metadata content
a) Questions addressed on grammar and paragraph construction. Done.
b) Problem with central meridian of projection. Document AML error. Done.
c) Attribute definition questions. Done.
4. Approved by Georgia District Chief, Tim Hale, on November 10 ,1997.
Related_Spatial_and_Tabular_Data_Sets
None.
Other References Cited
------, 1994, Medium Resolution Digital Vector Shoreline, NOAA, NOS,
Washington D.C.
______, 1990, TIGER/Line Precensus Files, 1990, U.S. Department of Commerce,
Bureau of Census, Washington D.C.
______, 1987, US GeoData Digital Elevation Models Data Users Guide,
Department of the Interior, US Geological Survey, Reston, VA.
Time Period of Content:
Time Period Information:
Single Date/Time:
Calendar Date: 1987
Currentness Reference: unknown
Status:
Progress: Complete
Maintenance and Update Frequency: None planned
Spatial Domain:
Bounding Coordinates:
West Bounding Coordinate: -85.498619
East Bounding Coordinate: -80.650047
North Bounding Coordinate: 34.970295
South Bounding Coordinate: 30.347689
Keywords:
Theme:
Theme Keyword Thesaurus: none
Theme Keyword: slope digital elevation model DEM 1-degree DMA
Place:
Place Keyword Thesaurus: none
Place Keyword: Georgia
Place Keyword: GA
Access Constraints: None
Use Constraints: None
Browse Graphic:
Browse Graphic File Name: <http://gis1.state.ga.us/discover/>
Browse Graphic File Description: Simple image file of the dataset
Browse Graphic File Type: GIF


Data Quality Information
Section Index

Attribute Accuracy:
Attribute Accuracy Report: See Logical Consistancy Report
Logical Consistency Report: Not applicable for raster data.
Completeness Report:
The DEM is visually inspected for completeness on a DEM view and edit system for the purpose of performing a final quality
control and if necessary edit of the DEM. The physical format
of each digital elevation model is validated for content
completeness and logical consistency during production quality
control and prior to archiving in the National Digital
Cartographic Data Base.
Level 2 DEM: Level 2 DEMs may contain void areas due to
interruptions to contours in the source graphic or DLG. Void area
elevation grid posts are assigned the value of -32,767. In addition,
suspect elevation areas may exist in the DEM but are not specifically
identified. Suspect areas can be located on the source graphic as a
"disturbed surface" which are symbolized by contours overprinted
with photorevised or other surface patterns.
Positional Accuracy:
Horizontal Positional Accuracy:
Horizontal Positional Accuracy Report:
Digital elevation models meet horizontal National Map Accuracy Standards (NMAS) accuracy requirements. NMAS horizontal accuracy
requires that at least 90 percent of points tested are within 0.02
inches of the true position. The primary reference from which 1-degree
DEM accuracy is derived is source-based, as a minimum, meeting NMAS for
100,000-scale USGS topographic series maps.
Quantitative Horizontal Positional Accuracy Assessment:
Horizontal Positional Accuracy Explanation: Resolution as reported
Vertical Positional Accuracy:
Vertical Positional Accuracy Report:
The vertical root-mean-square error (RMSE) statistic is used to describe the vertical accuracy of a DEM, encompassing both random and systematic
errors introduced during production of the data. The RMSE is encoded in
element number 5 of record C of the DEM. Accuracy is computed by a
comparison of linear interpolated elevations in the DEM with
corresponding known elevations. Test points are well distributed,
representative of the terrain, and have true elevations with accuracies
well within the DEM accuracy criteria. Acceptable test points include,
in order of preference: field control, aerotriangulated test points, spot
elevations, or points on contours from existing source maps with
appropriate contour interval. A minimum of 28 test points per DEM
(20 interior points and 8 edge points) is required to compute the RMSE.
Edge points are those which are located along, at, or near the
quadrangle neatlines and are deemed by the editor to be useful
to evaluating the accuracy of the edge of the DEM.

Collection of test point data and comparison of the DEM with the
quadrangle hypsography are conducted by the quality control units within
the USGS. There are three types of DEM vertical error; blunder,
systematic and random. These errors are reduced in magnitude by editing
but cannot be completely eliminated and may be encountered. Blunder
errors are those errors of major proportions and are easily identified
and removed during interactive editing. Systematic errors are those
errors that follow some fixed pattern and are introduced by data
collection procedures and systems. These error artifacts include:
vertical elevation shifts, misinterpretation of terrain surface due to
trees, buildings and shadows, and fictitious ridges, tops, benches or
striations. Random errors result from unknown or accidental causes. DEMs
are edited to correctly depict elevation surfaces that correspond to
water bodies of specified size. Level 2 DEM: A vertical RMSE of one-half
of the contour interval (of 100,000-scale source), determined by the
source map, is the maximum permitted. Systematic errors may not exceed
one contour interval, determined by the source map, is the maximum
permitted. Systematic errors may not exceed one contour interval
specified by the source graphic. Level 2 DEMs have been processed or
smoothed for consistency and edited to remove identifiable systematic
errors.
Cloud Cover: 0


Spatial Data Organization Information
Section Index

Direct Spatial Reference Method: Raster


Spatial Reference Information
Section Index

Horizontal Coordinate System Definition:
Planar:
Map Projection:
Map Projection Name: Lambert Conformal Conic
Lambert Conformal Conic:
Standard Parallel: 31.4166
Standard Parallel: 34.2833
Longitude of Central Meridian: -83.5
Latitude of Projection Origin: 0
False Easting: 0
False Northing: 0
Planar Coordinate Information:
Planar Coordinate Encoding Method: Coordinate Pair
Coordinate Representation:
Abscissa Resolution: 0.1
Ordinate Resolution: 0.1
Planar Distance Units: international feet
Geodetic Model:
Horizontal Datum Name: North American Datum of 1983
Ellipsoid Name: Geodetic Reference System 80
Semi-major Axis: 6378206
Denominator of Flattening Ratio: 294.9786982


Entity and Attribute Information
Section Index

Detailed Description:
Entity Type:
Entity Type Label: SLOPE250.VAT
Entity Type Definition: Slope in percent vertical over horizontal
Entity Type Definition Source: U.S. Geological Survey
Attribute:
Attribute Label: -
Attribute Definition: Slope in percent vertical over horizontal
Attribute Definition Source: U.S. Geological Survey
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: 0-110 percent
Enumerated Domain Value Definition: none
Attribute:
Attribute Label: COUNT
Attribute Definition: Number of GRID cells of a VALUE
Attribute Definition Source: Computed
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: Integer
Enumerated Domain Value Definition: none
Attribute:
Attribute Label: VALUE
Attribute Definition: Internal feature number for GRIDs
Attribute Definition Source: Computed
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: Integer
Enumerated Domain Value Definition: none
Detailed Description:
Entity Type:
Entity Type Label: SLOPE250.STA
Entity Type Definition: Statistics table
Entity Type Definition Source: GRID
Attribute:
Attribute Label: -
Attribute Definition: Statistics table
Attribute Definition Source: GRID
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: -
Enumerated Domain Value Definition: none
Attribute:
Attribute Label: MAX
Attribute Definition: Maximum GRID cell VALUE
Attribute Definition Source: Computed
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: Real number
Enumerated Domain Value Definition: none
Attribute:
Attribute Label: MEAN
Attribute Definition: Mean GRID cell VALUE
Attribute Definition Source: Computed
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: Real number
Enumerated Domain Value Definition: none
Attribute:
Attribute Label: MIN
Attribute Definition: Minimum GRID cell VALUE
Attribute Definition Source: Computed
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: Real number
Enumerated Domain Value Definition: none
Attribute:
Attribute Label: STDV
Attribute Definition: Standard Deviation of GRID cell VALUEs
Attribute Definition Source: Computed
Attribute Domain Values:
Enumerated Domain:
Enumerated Domain Value: Positive real number
Enumerated Domain Value Definition: none
Overview Description:
Entity and Attribute Overview:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME INDEXED? 1 VALUE 4 10 B - Indexed
5 COUNT 4 10 B - -
Value represents the slope of the grid cell in percent rise over horizontal
distance.
Count represents the number of grid cells of each value.
Entity and Attribute Detail Citation: Not Available


Distribution Information
Section Index

Distributor:
Contact Information:
Contact Organization Primary:
Contact Organization: Georgia GIS Data Clearinghouse
Contact Position: Database Manager
Contact Address:
Address Type: Mailing and Physical Address
Address:
University of Georgia, 1180 East Broad St., Suite 2076
City: Athens
State or Province: Georgia
Postal Code: 30602-5418
Country: USA
Contact Voice Telephone: (706) 542-0246
Contact Facsimile Telephone: (706) 542-6535
Contact Electronic Mail Address: gischouse@state.ga.us
Distribution Liability:
Georgia GIS Data Clearinghouse is charged by the State of Georgia with the development, maintenance and distribution of the State's geographic databases and, in cooperation with other organizations, is committed to offering its users accurate, useful, and current information about the state. Although every effort has been made toensure the accuracy of information, errors and conditions originating from physical sources used to develop the corporate database may be reflected in the data supplied. Users of this data must be aware of data conditions and bear responsibility for the appropriate use of the information with respect to possible errors, original map scale, collection methodology, currency of data, and other conditions specific to certain data. The Georgia GIS Data Clearinghouse makes no warranty, either expressed or implied, as to the accuracy or completeness of any information archived and distributed by the Clearinghouse. The digital information is distributed on a "as is" basis, and the Georgia GIS Data Clearinghouse shall not be responsible for any claims attributable to errors, omissions or other inaccuracies in the information. In no event shall Georgia GIS Data Clearinghouse be liable for direct, indirect, special, incidental or consequential loss or damage of any nature caused to any person, party or entity as a result of use of the information. Georgia GIS Data Clearinghouse does not support secondary distribution of this data. The use of trade names or commercial products does not constitute their endorsement by the Georgia GIS Data Clearinghouse or Georgia State Government.

The Georgia GIS Data Clearinghouse hereby disclaims liability for any such loss or damage.
Standard Order Process:
Digital Form:
Digital Transfer Information:
Format Name: ARCE
Format Version Number: 7.x
File Decompression Technique: ZIP
Digital Transfer Option:
Fees: None
Available Time Period:
Time Period Information:
Single Date/Time:
Calendar Date: Unknown


Metadata Reference Information
Section Index

Metadata Date: 10/14/1999
Metadata Review Date:
Metadata Future Review Date:
Metadata Contact:
Contact Information:
Contact Organization Primary:
Contact Organization: Georgia GIS Data Clearinghouse - Metadata
Contact Position: Metadata Developer
Contact Address:
Address Type: mailing and physical address
Address: Georgia Institute of Technology, 276 5th Street NW
City: Atlanta
State or Province: Georgia
Postal Code: 30332-0695
Country: USA
Contact Voice Telephone: (404) 894-0502
Contact Facsimile Telephone: (404) 385-0450
Contact Electronic Mail Address: gischouse@state.ga.us
Hours of Service: Monday-Friday 8:00 am - 5:00 pm
Metadata Standard Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata Time Convention: local time

SMMS Metadata report generated 10/14/99