Texas Digital Raster Graphics (DRGs)
DRG Metadata - Contains descriptive information about Digital Raster Graphics data (or Digital USGS Topographic Maps)
Table of Contents
- 1 - Identification Information
- 2 - Data Quality Information
- 3 - Spatial Data Organization Information
- 4 - Spatial Reference Information
- 5 - Entity and Attribute Information
- 6 - Distribution Information
- 7 - Metadata Reference Information
The following text conforms with the hierarchy of data elements in the FGDC Content Standards for Digital Geospatial Metadata. This GIS layer supersedes all earlier copies, translations or coverages of the Air Quality Monitoring Stations coverage which may have been made by the Texas Commission on Environmental Quality (TCEQ).
1 IDENTIFICATION_INFORMATION:1.1 Citation:
8.1 Originator: U.S. Geological Survey, EROS Data Center
8.2 Publication_Date: 1996-1997
8.4 Title: Digital Raster Graphics (DRGs)
8.6 Geospatial_Data_Presentation_Form: map
8.8 Publication_Information:
8.8.1 Publication_Place: Sioux Falls, SD
8.8.2 Publisher: U.S. Geological Survey, EROS Data Center
1.2 Description:
1.2.1 Abstract:
The Texas Commission on Environmental Qaulity has
acquired digital raster graphics (DRGs) from the U.S.
Geological Survey for the entire state of Texas and some
neighboring areas outside the state border. A DRG is a
scanned image of a USGS topographic map, including all
map collar information. The image inside the map neatline
is georeferenced to the surface of the Earth. The DRGs
available are of the 1:24,000, 1:100,000 and
1:250,000-scale topographic map series.
DRGs can be used to collect, review, and revise other
digital data, especially digital line graphs (DLGs). When
the DRG is combined with other digital products, such as
digital orthophoto quadrangles (DOQs) or digital elevation
models (DEMs), the resulting image provides additional
visual information for the extraction and revision of base
cartographic information.
1.2.2 Purpose:
For general purpose use, to be utilized by TCEQ staff and
external customers.
DRGs can be for validating digital line graphs (DLGs)
and DLGS data collection and revision. DRGs can also help
assess the completeness of digital data from other mapping
agencies. They can be used to produce "hybrid" products,
including combined DRGs and DOQs for revising and collecting
digital data, DRGs and DEMs for creating shaded-relief DRGs,
and combinations of DRG, DOQS, and DLGS data. Although a
standard DRG is an effective mapping tool, its full potential
for digital production is realized in combination with other
digital data.
1.2.3 Supplemental_Information:
Supplemental information about DRGs, including Standards for
Digital Raster Graphics, can be obtained at
http://topomaps.usgs.gov/drg/
. The USGS documentation for DRGs can be obtained on-line
at http://topomaps.usgs.gov/drg/
. Metadata files can also be obtained from the original CDs
housed at TNRIS. NOTE: Projection information for a specific
DRG can be found in its individual metadata file.
The DRG files available from TCEQ follow the USGS topographic
map naming convention. In this convention:
Characters 1-2 represent the southeast latitude of the
one-degree area containing the DRG.
Characters 3-5 represent the southeast longitude of the
one-degree area containing the DRG.
Characters 6-7 represent the USGS Map Index Number, a
two-character alphanumeric code locating the quadrangle
within the one-degree area. NOTE: Normally the alpha
character would be capitalized however due to a confirmed
software bug in Arc/Info release 7.1.1, TCEQ has renamed
all DRGs so that this character is lowercase.
For example, the Pflugerville-W 7.5-minute DRG is named
30097d6.tif.
1.3 Time_Period_of_Content:
9.3 Range_of_Dates/Times:
9.3.1 Beginning_Date: Unknown
9.3.3 Ending_Date: Unknown
1.3.1 Currentness_Reference:
USGS topographic maps are the source data for the DRGs.
Exact dates of the source data can be obtained in the map
collar information on the DRG.
1.4 Status:
1.4.1 Progress: Complete
1.4.2 Maintenance_and_Update_Frequency: As needed
1.5 Spatial_Domain:
1.5.1 Bounding_Coordinates:
1.5.1.1 West_Bounding_Coordinate: -107
1.5.1.2 East_Bounding_Coordinate: -92
1.5.1.3 North_Bounding_Coordinate: 37
1.5.1.4 South_Bounding_Coordinate: 25
1.6 Keywords:
1.6.1 Theme:
1.6.1.1 Theme_Keyword_Thesaurus: None
1.6.1.2 Theme_Keyword: quads
1.6.1.2 Theme_Keyword: quadrangles
1.6.1.2 Theme_Keyword: 7.5'
1.6.1.2 Theme_Keyword: 7.5-minute
1.6.1.2 Theme_Keyword: 7.5 minute
1.6.1.2 Theme_Keyword: index
1.6.1.2 Theme_Keyword: topographic
1.6.1.2 Theme_Keyword: topo
1.6.1.2 Theme_Keyword: USGS topographic maps
1.6.1.2 Theme_Keyword: USGS topo maps
1.6.1.2 Theme_Keyword: USGS maps
1.6.2 Place:
1.6.2.1 Place_Keyword_Thesaurus: FIPS 5-2
1.6.2.2 Place_Keyword: TX
1.7 Access_Constraints: None
1.8 Use_Constraints: None
1.9 Point_of_Contact:
10.1 Contact_Person_Primary:
10.1.1 Contact_Person: Greg Smithhart
10.1.2 Contact_Organization: TCEQ
10.4 Contact_Address:
10.4.1 Address_Type: Mailing address
10.4.2 Address: P.O. Box 13087 (Mail Code 197)
10.4.3 City: Austin
10.4.4 State_or_Province: TX
10.4.5 Postal_Code: 78711-3087
10.4.6 Country: USA
10.5 Contact_Voice_Telephone: 512-239-0859
10.7 Contact_Facsimile_Telephone: 512-239-0888
10.8 Contact_Electronic_Mail_Address:
gsmithha@tceq.texas.gov
1.10 Browse_Graphic:
1.10.1 Browse_Graphic_File_Name:
http://www.tceq.state.tx.us/assets/public/gis/metadata/images/drg.gif
1.10.2 Browse_Graphic_File_Description: None.
1.10.3 Browse_Graphic_File_Type: GIF
1.11 Data_Set_Credit: USGS
1.13 Native_Data_Set_Environment: UNIX
2 DATA_QUALITY_INFORMATION:
2.1 Attribute_Accuracy:
2.1.1 Attribute_Accuracy_Report:
The DRG uses a standard palette to ensure uniform color
throughout a particular map series. The RGB values for a
color, therefore, will remain consistent throughout that
DRG series. Although the color values of the DRG may
sometimes match those of the paper source map, a user will
usually notice small differences between the colors on the
digital image and on the paper map. Also, the quality of the
user's monitor affects the DRG color displayed. Although
the DRG generally contains the complete content of the
source map, features may occasionally be blurred because of
substandard source materials. The DRG also may contain
misclassified pixels (color noise).
The DRG is an 8-bit color image that employs a color palette
to ensure uniform colors throughout a particular DRG series.
All DRGs within a series must have the same RGB value.
2.2 Logical_Consistency_Report:
The USGS DRG was produced with the intention of replicating
as close as possible the original source map. Users of the
DRG will note, however, that a certain amount of "noise" can
be discerned when small areas are blown up or viewed under
zoomed-in conditions. This noise is in the form of random
specks or pixels of color and halos due to any number of
factors, such as, the quality of the source, the use of
screens and patterns on the litho, and the unevenness of ink
due to saturation and absorption. Discontinuities or breaks
in linear features may also be present and are due to improper
calibration or usage of the scanner, the condition of the
source, and resampling. Descreening, quantizing, and noise
filtering are methods used to reduce noise, which, besides
creating a more aesthetically pleasing image, have the added
benefit of reducing the size of the image file. Removal of
lithographic screen patterns is preferred but not required.
2.3 Completeness_Report:
Image completeness was checked by visually inspecting a sampling
of DRGs. Each selected DRG was examined for gaps (missing data)
in the main body of the map, the map collar, the over-edge areas,
and any insets.
2.4 Positional_Accuracy:
2.4.1 Horizontal_Positional_Accuracy:
2.4.1.1 Horizontal_Positional_Accuracy_Report:
Random samplings of DRGs were accuracy tested by USGS
and/or the originator of the data. The accuracy test
was performed by comparing the positions of UTM grid
intersections against the corresponding location on the
digital image. A visual inspection determined whether
those coordinates fell within the pixels that define a
grid tick. DRGs duplicate the horizontal accuracy of
their source.
In addition, a stratified random sample of DRGs were
accuracy-tested by TCEQ GIS Section staff members.
Individual quadrangle polygons were mathematically
generated and then projected using an AML program. These
polygons were then overlaid with the respective DRG.
The maximum offset was measured at a zoom ratio of 1:1.
The error ranged from 2 meters to 13 meters.
2.4.1.2 Quantitative_Horizontal_Positional_Accuracy_Assessment:
2.4.1.2.1 Horizontal_Positional_Accuracy_Value:0
2.4.1.2.2 Horizontal_Positional_Accuracy_Explanation:
DRGs will retain the horizontal accuracy of the
source maps. Most USGS printed maps contain the
National Map Accuracy Standards (NMAS) note in
the collar area. The NMAS states that for maps on
publication scales of 1:20,000 or smaller, not more
than 10% of the points tested shall be in error by
more than 1/50 inch measured on the publication scale.
Test points must be "well defined", that is, easily
visible or recoverable on the ground. For DRGs this
accuracy statement applies only to the area of the
DRG that falls within the neatline of the source map
(excluding inset areas). Over-edge areas falling
outside the transformation boundary area (the map
neatline), can exhibit anomalies or discrepancies.
These anomalies will also appear in the map inset
areas and in the map collar. For maps without the
NMAS note, the horizontal accuracy is unknown.
However, the DRG will retain the accuracy of the
source map.
2.5 Lineage:
2.5.1 Source_Information:
2.5.1.1 Source_Citation:
8.1 Originator: U.S. Geological Survey, EROS Data Center
8.2 Publication_Date: 1996-1997
8.4 Title: Digital Raster Graphics (DRGs)
8.8 Publication_Information:
8.8.1 Publication_Place: Sioux Falls, SD
8.8.2 Publisher: U.S. Geological Survey, EROS Data Center
2.5.1.2 Source_Scale_Denominator: 24000
2.5.1.3 Type_of_Source_Media: paper
2.5.1.4 Source_Time_Period_of_Content:
2.5.1.4.1 Source_Currentness_Reference: publication date
2.5.1.5 Source_Citation_Abbreviation: USGS Topo
2.5.1.6 Source_Contribution:
The standard area of coverage of a DRG is the entire area
printed on a USGS topographic map including the map collar,
any over-edge areas, and insets.
2.5.2 Process_Step:
2.5.2.1 Process_Description:
A detailed description of USGS DRG processing and process
contact information can be obtained at
http://topomaps.usgs.gov/drg/drg_technical.html
. DRGs were copied from the original CDs received from USGS
at TCEQ. The original CDs were delivered to TNRIS.
A program was run to drop the first character (known as
"Category" in USGS's DRG file naming convention) from each
DRG's image (.TIF) and world (.TFW) files for consistency
purposes; the USGS DEMs are named in this manner. Information
on USGS's DRG naming convention can be found at
http://topomaps.usgs.gov/drg/drg_name.html
.3 SPATIAL_DATA_ORGANIZATION_INFORMATION:
3.2 Direct_Spatial_Reference_Method: Raster
3.4 Raster_Object_Information:
3.4.1 Raster_Object_Type: Pixel
4 SPATIAL_REFERENCE_INFORMATION:
4.1 Horizontal_Coordinate_System_Definition:
4.1.2 Planar:
4.1.2.1 Map_Projection:
4.1.2.1.1 Map Projection Name: Transverse_Mercator
4.1.2.2 Grid_Coordinate_System:
4.1.2.2.1 Grid Coordinate System Name: Universal Transverse Mercator
4.1.2.2.2 Universal_Transverse_Mercator:
4.1.2.2.2. UTM Zone Number: 13,14,15
4.1.4 Geodetic_Model:
4.1.4.1 Horizontal_Datum_Name: The datum used is the datum of the
DRG source (e.g. NAD27, NAD83).
4.1.4.2 Ellipsoid_Name: The ellipsoid used is the ellipsoid of the
DRG source (e.g. Clarke 1866, GRS 1980)
5 ENTITY_AND_ATTRIBUTE_INFORMATION:
5.2 Overview Description:
5.2.1 Entity_and_Attribute_Overview:
Each raster entity or pixel contains a digital number from 0
through 12 referencing a color palette of RGB values from 0
through 255 in which the standard colors used in the DRG are
defined. 5.2.2 Entity_and_Attribute_Detail_Citation:
USGS National Mapping Program Technical Instructions
Standards for Digital Raster Graphics
6 DISTRIBUTION_INFORMATION:
6.1 Distributor:
10.1 Contact_Person_Primary: Greg Smithhart
10.2 Contact_Organization_Primary: TCEQ
10.4 Contact_Address:
10.4.1 Address_Type: mailing address
10.4.2 Address: P. O. Box 13087 (Mail Code 197)
10.4.3 City: Austin
10.4.4 State_or_Province: TX
10.4.5 Postal_Code: 78711-3087
10.4.6 Country: USA
10.5 Contact_Voice_Telephone: 512-239-0859
10.7 Contact_Facsimile_Telephone: 512-239-0888
10.8 Contact_Electronic_Mail_Address: gsmithha@tceq.texas.gov
6.2 Resource_Description: TCEQ Certified Base Map Layers
6.3 Distribution_Liability:
Although these data have been processed successfully on a
computer system at the USGS, no warranty expressed or implied
is made by the USGS or TCEQ regarding the utility of the data
on any other system, nor does the act of distribution constitute
any such warranty.
6.4 Standard_Order_Process:
6.4.2 Digital_Form:
6.4.2.1 Digital_Transfer_Information:
6.4.2.1.1 Format_Name: Tagged Image File Format (TIFF)
6.4.2.1.2 Format_Version_Number: 6.0
6.4.2.1.3 Format_Version_Date:
6.4.2.1.4 Format_Specification:
Links to GeoTiff and TIFF 6.0 format specifications can
be found here http://topomaps.usgs.gov/drg/
.6.4.2.1.5 Format_Information_Content:
To facilitate file manipulation by the widest possible
range of potential users, data and text files conform
to the USGS topographic map naming convention. The
associated DRG image (.TIF), world (.TFW), and metadata
(.FGD) files incorporate an intelligent data set name
consisting of descriptive metadata wrapped around a
standardized kernel that describes the spatial location
of the file. The intent of this file naming protocol is
to positively identify the spatial identity of the file.
6.4.2.1.6 File_Decompression_Technique: PackBits
6.4.2.1.7 Transfer_Size: 2 MB to 25 MB
6.4.2.2 Digital_Transfer_Option:
6.4.2.2.1 Online_Option:
6.4.2.2.1.1 Computer_Contact_Information: World Wide Web
6.4.2.2.1.1.1 Network_Address: www.tceq.state.tx.us
6.4.2.2.1.1.1.1 Network_Resource_Name: http://www.tceq.state.tx.us/gis/
6.7 Available_Time_Period: Immediate
7 METADATA_REFERENCE_INFORMATION:
7.1 Metadata_Date: 19980309
7.2 Metadata_Review_Date: 19980309
7.3 Metadata_Future_Review_Date: Unknown
7.4 Metadata_Contact:
10.1 Contact_Person_Primary: Greg Smithhart
10.2 Contact_Organization_Primary: TCEQ
10.4 Contact_Address:
10.4.1 Address_Type: mailing address
10.4.2 Address: P. O. Box 13087 (Mail Code 197)
10.4.3 City: Austin
10.4.4 State_or_Province: TX
10.4.5 Postal_Code: 78711-3087
10.4.6 Country: USA
10.5 Contact_Voice_Telephone: 512-239-3850
10.7 Contact_Facsimile_Telephone: 512-239-0888
10.8 Contact_Electronic_Mail_Address:
gsmithha@tceq.texas.gov
7.5 Metadata_Standard_Name:
FGDC Content Standards for Digital Geospatial Metadata
7.6 Metadata_Standard_Version: 19940608
7.7 Metadata_Time_Convention: Local Time
7.8 Metadata_Access_Constaints: None
7.9 Metadata_Use_Constaints: None
7.10 Metadata_Security_Information:
Metadata_Security_Classification_System: None
Metadata_Security_Classification: Unclassified
