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Center for Spatial Analysis Technologies



Digital Environmental Atlas of Georgia


Image of Digital Environmental Atlas CDs

by S. Jack Alhadeff 1, Jonathan W. Musser 1, Alan C. Sandercock 2, and Thomas R. Dyar 1

Georgia Geologic Survey Report CD-1

1 U.S. Geological Survey
2 Georgia Department of Natural Resources, Environmental Protection Division, Georgia Geologic Survey

ABSTRACT

 This CD-ROM set contains 38 digital map data sets covering the State of Georgia that will be useful to the general public, private industry, schools, and government agencies. The data sets include: Towns and Cities, Public Lands, State Parks, Trails and Greenways, County Boundaries, Geographic Names, Hydrologic Units, Shorelines, Soils, Landcover, Major Roads, Public Airports, River Reach - Major Streams, Roads, Ground-Water Site Inventory, Hydrography, 7.5 Minute Quadrangle Index, Surface Water Monitoring Stations, Contours, 1:250,000-scale Digital Elevation Model, 1:100,000-scale Digital Raster Graphic, 1:250,000-scale Digital Raster Graphic, 1:500,000-scale Digital Raster Graphic, Level-I Landuse/Landcover, Level-II Landuse/Landcover, Pipelines, Transmission Lines and Miscellaneous Transportation, Railroads, River Corridors with Mean Annual Flow Greater than Four Hundred Cubic Feet Per Second, 1:250,000-scale Slope, National Forests, Physiographic Provinces, Surficial Geology, Geologic Faults, Geologic Dikes, Ground-Water Pollution Susceptibility, Most Significant Ground-Water Recharge Areas, and the Georgia Department of Transportation State Highway Map.

ArcExplorer (r) Version 1.1 software, by Environmental Systems Research Institute, Inc., is included on these CD-ROMs. (Any use of trade names in this publication is for descriptive purposes only and does not imply endorsement by the State of Georgia or by the U.S. Government). ArcExplorer allows the user to display combinations of data sets and attributes using selected colors and patterns. Spatial and logical queries also can be performed to locate selected sets of attributes. Metadata (documentation) files containing detailed information about each data set and the procedures used to create it are included on these CD-ROMs.

INTRODUCTION

 The 38 digital-map data sets on this two CD-ROM set have been compiled to provide a set of basic Statewide geographic data suitable for use with Geographic Information System (GIS) software. The collection of data sets is intended to benefit people just learning to use GIS as well as experienced GIS users. Most of the data sets are developed from 1:100,000-scale maps (on which one inch equals about 1.6 miles) and provide a level of spatial detail convenient for users interested in geographic areas ranging from a few square miles, to watersheds, counties, or the entire State.

The data sets may be displayed on personal computers using the included viewer software ArcExplorer(r) Version 1.1. (referred to in this report as ArcExplorer) by Environmental Systems Research Institute, Inc. (Any use of trade names in this publication is for descriptive purposes only and does not imply endorsement by the State of Georgia or by the U.S. Government).

Data set compilation was funded under a cooperative Joint Funding Agreement between the U.S. Geological Survey and the Georgia Department of Natural Resources, Environmental Protection Division, Geologic Survey Branch. Other cooperators who have assisted with this effort include the Georgia Department of Natural Resources, Wildlife Resources Division, the Georgia Department of Natural Resources, State Parks, Recreation and Historic Sites, and the Georgia Department of Transportation. The U.S. Natural Resources Conservation Service, the U.S. Forest Service, the U.S. Fish and Wildlife Service, and the U.S. Environmental Protection Agency all contributed data sets to the CD-ROMs.

The authors wish to acknowledge the following individuals for technical reviews, advice, and assistance: Keith W. McFadden, Diane C. Burgoon and Robert R. Pierce of the U.S. Geological Survey; and Elizabeth Cheney, Victoria P. Trent, David R. Hipple and Christopher G. Canalos of the Georgia Department of Natural Resources.

GETTING STARTED

The digital-map data sets are designed to be used with the ArcExplorer viewing software, which is provided on this CD-ROM set. ArcExplorer runs under the Microsoft(r) Windows 95(r), Windows 98(r), or Windows NT(r) version 4.0 operating systems or later. The data sets on these CD-ROMs are also compatible with versions 2.1 through 3.2 of ArcView(r). Table 1 provides minimum and recommended system requirements for running ArcExplorer.

Table 1. Minimum and recommended hardware requirements for using these CD-ROMs with ArcExplorer


Minimum Requirements
System Feature            Windows 95    Windows NT
                          or later      4.0 or later
System RAM                8 MB          16 MB
CPU                       486DX 33      486DX 33
Video Adapter             VGA           VGA
Free Disk Space           5 MB          5 MB
CD-ROM Reader             4x or faster  4x or faster

Recommended
System Feature            Windows 95    Windows NT
                          or later      4.0 or later
System RAM                32 MB or      64 MB or 
                          better        better
CPU                       Pentium 90    Pentium 90 
                          or better     or better
Video Adapter             PCI Video     PCI Video
                          Card          Card
Free Disk Space           10 MB         10 MB
CD-ROM Reader             12x or faster 12x or faster


Note: As with most Windows software, performance will improve with more memory and faster systems.
There are two CD-ROMs included in this report (see Table 2). CD-ROM 1 contains the ArcExplorer installation software, thirty-five data layers, associated documentation, and project files for ArcExplorer (.AEP extensions) and ArcView (.APR extensions), while CD-ROM 2 contains two data layers, associated documentation and project files for ArcExplorer and ArcView. The ArcExplorer project file ATLAS1.AEP (on CD-ROM 1) can be used with data on CD-ROM 1, while the project file ATLAS2.AEP (on CD-ROM 2) can be used with data on CD-ROM 2. The project file ATLAS1_2.AEP (on CD-ROM 1) can be used with data from both CD- ROMs copied to a common location (see SUGGESTIONS FOR IMPROVING SYSTEM PERFORMANCE).

Installation of ArcExplorer requires approximately 5-10 MB of free space on the hard disk. After inserting CD-ROM 1 on your computer, ArcExplorer can be then be installed from the Windows 95/98, or Windows NT environment using Run on the Start Bar (browsing the CD-ROM drive for the folder \ARCEXPL, double-clicking on this folder, double-clicking on the file AECLIENT.EXE and following the installation instructions) or by locating the file AECLIENT.EXE located in the \ARCEXPL folder using Windows Explorer(r), double-clicking on the file and following the installation instructions. Windows NT users may need administrator access in order to install ArcExplorer.

USING ARCEXPLORER

 Once ArcExplorer is installed,the user is encouraged to view the ArcExplorer Users Guide, ARCEXPL.PDF located on CD-ROM 1 in the \ARCEXPL folder. This file may be viewed by using Adobe's ACROBAT(r) version 4.0 READER to browse or print this file. The ACROBAT installation file, AR40ENG.EXE, is found in the \ACROBAT folder and may be installed similarly to ArcExplorer. Detailed examples using the Statewide data from the CD-ROMs are shown in the file USING.PDF (on CD-ROM 1), which can be read by ACROBAT.

The user may then run the Digital Environmental Atlas of Georgia by opening the ArcExplorer project file ATLAS1.AEP (on CD-ROM 1). This project file contains colors and classifications developed by the authors for the Digital Environmental Atlas of Georgia. The user is free to use these definitions as a starting point to explore the information contained on the CD-ROMs.

The user may maximize the window to fit the computer screen and enlarge the width of the legend by dragging the border between the legend and the map to the right. Themes with a checked box are displayed on the screen in the order that they appear from the bottom of the legend to the top. The user may change the order a theme is drawn, by clicking and dragging the theme up or down in the legend. Many of the themes display too much detail to be usable when displaying the entire State. A theme may be made active for query, identification or symbolization by clicking on its name in the legend. When a theme is active, it appears as raised in the legend. Users should use the zoom tools to zoom to a smaller area before displaying many themes. Users may perform spatial and logical queries to locate a specific set of attribute characteristics. Users may modify and customize the project files and save them to new files on hard disk or diskette, but the files on the CD-ROMs cannot be modified on the CD-ROM media. Additional information on the capabilities of ArcExplorer may be found in the ArcExplorer User's Guide.

As a stand-alone GIS software product, ArcExplorer is a relatively complete data explorer, allowing users to display and query a wide variety of standard data sources. With ArcExplorer the user can utilize ARC/INFO(r) coverages and image- formatted data (.TIF extensions) located in the \DATA directories on the CD- ROMs to pan and zoom through the multiple map layers, display data using classifications, symbols and labeling, and identify and query geographic and attribute data. Other features provide for the use of legends, the inclusion of overview maps, the creation of multiple views, saving and retrieving views, and the printing of maps.

The A_README.TXT file provides important general information about the organization of the CD-ROMs and the individual data layers. Complete documentation files for each data layer are stored in the \METADATA subdirectory. The documentation files are in Federal Geographic Data Committee (FGDC) Metadata format (Federal Geographic Data Committee, 1994).

DATA QUALITY STATEMENT

 These data layers are compiled from many different sources of varying quality, but are the best available given the scope of the project. Complete and thorough checking of the data was not possible, and some known problems exist. Much of this is due to different sources for the data sets, and features common to multiple data layers may not match. For example, streams that represent county boundaries from the hydro data layer may not match the county boundaries of the county data layer. Users should exercise caution and judgment in applying these data, and be aware that errors may be present in any or all of the digital map data sets.

DATA FORMATS

 These CD-ROMs comply with the ISO 9660 standard for CD-ROMs. The CD-ROMs and data layers are readable with UNIX, Macintosh, and personal computers equipped with the appropriate CD-ROM reader and software. The current version of ArcExplorer contained on these CD-ROMs can be used only on personal computers using the Microsoft Windows 95/98 or Windows NT operating systems. However, the CD-ROMs may be used with ArcView under the Microsoft Windows 95/98, Windows NT or UNIX operating systems as well as with ARC/INFO under the Microsoft Windows NT or UNIX operating systems.

All data layers are stored in ARC/INFO coverage formats except for the 1:100,000- scale Digital Raster Graphic, the 1:250,000-scale Digital Raster Graphic, the 1:250,000-scale Digital Elevation Model, the 1:250,000-scale Slope and the 1:24,000- scale Landcover data layers, which are stored as Tagged Image File Formats (.TIF), Pack-bit Compressed with an associated georeferencing world file (.TFW). The 1:250,000-scale Digital Elevation Model, the 1:250,000- scale Slope and the 1:24,000- scale Landcover data layers are also stored as ARC/INFO GRID (r) files to allow users with ARC/INFO or ArcView software to benefit from their information content. Also, dBASE(r) formatted files from the U.S. Natural Resources Conservation Service STATSGO Soils are included for users with ARC/INFO or ArcView software. Three Tagged Image File Formats (.TIF), Pack-bit Compressed with an associated georeferencing world file (.TFW) are included to give the user an explanation or legend of the colors used for the 1:250,000-scale Slope, 1:250,000-scale Digital Elevation Model and Landcover data sets.

Table 2. Organization of data layers and related files on the CD-ROMs.

                                        CD-ROM 1

\ Root Directory
  A_NOTICE.TXT            Liability disclaimer
  A_README.TXT            Main Readme File
  ATLAS1.AEP              ArcExplorer 1.1 project file for the data contained on
                          this CD-ROM
  ATLAS1_2.AEP            ArcExplorer 1.1 project file for the data contained on 
                          both CD-ROMs
  ATLAS1.APR              ArcView 3.1 project file for the data contained on  
                          this CD-ROM
  ATLAS1_2.APR            ArcView 3.1 project file for the data contained on 
                          both CD-ROMs
  USING.PDF               Using ArcExplorer with the Digital Environmental
                          Atlas of Georgia in portable document format (pdf)
  \ACROBAT\
  AR40ENG.EXE             Adobe Acrobat Reader version 4.0 portable document 
                          format (pdf) viewer (self-installing archive and 
                          associated files)
  \ARCEXPL\
  AECLIENT.EXE            Data viewer software ArcExplorer version 1.1 (self-
                          installing archive and associated files)
  ARCEXPL.PDF             ArcExplorer users guide, Using ArcExplorer, ESRI, 
                          1998, in portable document format (pdf)
  \DATA\                  Statewide Data Layers in ARC/INFO coverages.
                          (including GRID coverages) or Image Formats

File Name    Description

airports    Public Airports
brevzone    Brevard Fault Zone (zone of cataclasis)
conserv     Public Lands, conservation lands
contours    Contours
corridor    River Corridors with Mean Annual Flow Greater than Four Hundred 
            Cubic Feet Per Second
county      County Boundaries
dem250      1:250,000-scale Digital Elevation Model - GRID
dikes       Diabase dikes
drastic     Ground-Water Pollution Susceptibility
faults      Faults, inferred faults, microbreccia zones, mylonite zones, and 
            shear zones
forest      National Forests
geology     Geology 
gnis        Geographic Names
gwsi        Ground-Water Site Inventory
huc250      Hydrologic Units
hydro       Hydrography
landcov     Landcover - GRID 
landuse1    Level-I Landuse / Landcover
landuse2    Level-II Landuse / Landcover
misctrns    Pipelines, Transmission Lines and Miscellaneous Transportation
mjr_rds     Major Roads
physio      Physiographic Provinces
quad24      7.5 Minute Quadrangle Index
rail        Railroads
recharge    Most Significant Ground-Water Recharge Areas
rf3mjr      River Reach - Major Streams
roads       Roads
shore       Shorelines
slope250    1:250,000-scale Slope - GRID
st_park     State Parks
statsgo     Soils
swsites     Surface Water Monitoring Stations
towns       Towns and Cities
trails      Trails and Greenways

Files in Tagged Image File Format (.TIF) with georeferenced world files (.TFW)

File Name             Description

dem250.tif            1:250,000-scale Digital Elevation Model
dotmapga.tif		     Georgia Department of Transportation 
                      State Highway Map
drg500.tif            1:500,000-scale Digital Raster Graphic
landcov.tif           Landcover
slope250.tif          1:250,000-scale Slope

The following files in Tagged Image File Format (.TIF) with georeferenced world 
files (.TFW) are included to give the user an explanation or legend of the 
colors used for the 1:250,000-scale Slope, 1:250,000-scale Digital Elevation 
Model and Landcover data sets.

File Name            Description

leg_dem.tif          Legend for1:250,000-scale Digital Elevation Model
leg_lc.tif           Legend for Landcover
leg_slp.tif          Legend for 1:250,000-scale Slope

  \DBASE\        dBASE formatted files of U.S. Natural Resources Conservation 
                 Service STATSGO Soil Attributes.

  \METADATA\     Complete FGDC Metadata text files for each data layer 

File Name            Description

airports.txt         Public Airports
brevzone.txt         Brevard Fault Zone (zone of cataclasis)
conserv.txt          Public Lands, conservation lands
contours.txt         Contours
corridor.txt         River Corridors with Mean Annual Flow Greater than Four 
                     Hundred Cubic Feet Per Second 
county.txt           County Boundaries
dem250.txt           1:250,000-scale Digital Elevation GRID / TIF
dikes.txt            Diabase dikes
dotmapga.txt         Georgia Department of Transportation State Highway Map
drastic.txt          Ground-Water Pollution Susceptibility
drg500.txt           1:500,000-scale Digital Raster Graphic
faults.txt           Faults, inferred faults, microbreccia zones, mylonite 
                     zones, and shear zones
forest.txt           National Forests
geology.txt          Geology
gnis.txt             Geographic Names
gwsi.txt             Ground-Water Site Inventory
huc250.txt           Hydrologic Units
hydro.txt            Hydrography
landcov.txt          Landcover - GRID / TIF
landuse1.txt         Level-I Landuse / Landcover
landuse2.txt         Level-II Landuse / Landcover
misctrns.txt         Pipelines, Transmission Lines and Miscellaneous
                     Transportation
mjr_rds.txt          Major Roads
physio.txt           Physiographic Provinces
quad24.txt           7.5 Minute Quadrangle Index
rail.txt             Railroads
recharge.txt         Most Significant Ground-Water Recharge Areas
rf3mjr.txt           River Reach - Major Streams
roads.txt            Roads
shore.txt            Shorelines
slope250.txt         1:250,000-scale Slope GRID / TIF
st_park.txt          State Parks
statsgo.txt          Soils
swsites.txt          Surface Water Monitoring
towns.txt            Towns and Cities
trails.txt           Trails and Greenways

                                         CD-ROM 2

\ Root Directory
  A_NOTICE.TXT    same as CD-ROM 1
  A_README.TXT    same as CD-ROM 1
  ATLAS2.AEP      ArcExplorer 1.1 project file for the data contained on this 
                  CD-ROM
  ATLAS2.APR      ArcView 3.1 project file for the data contained on this CD-ROM

  \DATA\          Statewide Data Layers

Files in Tagged Image File Format (.TIF) with georeferenced world files (.TFW)

File Name            Description

drg100.tif           1:100,000-scale Digital Raster Graphic
drg250.tif           1:250,000-scale Digital Raster Graphic

  \METADATA\     Complete FGDC Metadata text files for each data layer

File Name            Description

drg100.txt           1:100,000-scale Digital Raster Graphic
drg250.txt           1:250,000-scale Digital Raster Graphic


GEOMETRIC REGISTRATION

 The Albers Equal Area map projection (Snyder, 1987) is used for the data sets. This projection is appropriate for maps of the conterminous United States because of the visual presentation and equal-area characteristic, which facilitates areal analysis. This projection is frequently used for nationwide digital map data sets. The projection is cast on the North American Datum of 1983. Map projection information is provided in Table 3. This projection slightly distorts shapes and distances (scale) in order to maintain equal-area properties. Scale is true along the standard parallels, which are to the north and south of Georgia. Scale distortion in Georgia reaches a maximum of slightly less than one percent at the northern border of the state (Snyder, 1987.)

Table 3. Albers Equal Area projection parameters [GRS80, Geodetic Reference System 1980; NAD83, North American Datum 1983]

Projection parameters:

Spheroid                        CLARKE1866
Datum                           NAD27
First standard parallel         29 30 00 North
Second standard parallel        45 30 00 North
Central meridian                83 30 00 West
Latitude of projection origin   23 00 00 North

Coordinate system parameters:

False easting                   0.0
False northing                  0.0
Planimetric units of measure    meters


SUGGESTIONS FOR IMPROVING SYSTEM PERFORMANCE

 The data sets on these CD-ROMs are quite large, and, subsequently, system performance can be quite slow, especially with older computers and slower CD- ROM drives. One way to improve system performance is to copy the most frequently needed data sets to hard disk. For example, a user interested in a few Statewide data sets may want to copy those data sets in the \DATA subdirectory to hard disk. Windows Explorer may be used to copy directories from the CD to the hard disk. It is important to copy the \DATA\INFO directory along with any of the Statewide data sets (e.g. the \DATA\AIRPORTS directory), since each ARC/INFO coverage consists of a directory containing many files and associated attributes contained in the INFO directory. When copying the TIFF files to hard disk, it is necessary to copy files with both the .TIF and .TFW file extensions (e.g., the drg100.tif and drg100.tfw files).

Another way to improve system performance is to avoid displaying large polygon data layers as solid-filled polygons. The polygon boundaries may be displayed much more quickly than solid-filled polygons, but may not be queried for polygon attributes. Polygon data sets which may display slowly are: geology, landuse1 and landuse2. The 1:100,000-scale, 1:250,000-scale, and 1:500,000- scale Digital Raster Graphic TIFF images, drg100.tif, drg250.tif and drg500.tif, respectively, also may display slowly. For those users who need to access both CD-ROMs and need to improve overall performance, it is necessary to have approximately 1250 megabytes of storage available on the computer's hard disk. Using Widows Explorer, create a new folder (choose any name) on this hard disk, copy the \DATA directory, the ATLAS1_2.AEP file, and the ATLAS1_2.APR file from CD-ROM 1 to this folder. Replace CD-ROM 1 with CD-ROM 2, and copy the drg100.tif file and the drg100.tfw file in the \DATA directory on this CD-ROM to the DATA directory in the new folder of the hard disk. Use the ATLAS1_2.AEP and ATLAS1_2.APR project files when accessing the data through ArcExplorer and ArcView, respectively.

NOTES

File names, directories, and pathnames in this document are type set in upper case. Pathnames use MS-DOS-style naming conventions, with the "\" character indicating the highest-level directory of the CD-ROM.

REFERENCES CITED

 
Environmental Systems Research Institute, 1998, Using ArcExplorer, ESRI, 
Redlands, CA, 81 p.

Federal Geographic Data Committee, 1994, Content standards for digital 
geospatial  metadata (June 8): Federal Geographic Data Committee, Washington, 
D.C., 78 p.

Snyder, J.P., 1987, Map projections--A working manual: U.S. Geological Survey  
Professional Paper 1395, Reston, VA, 383 p.

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