Digital Raster Graphics (DRG), 1:24,000 for Minnesota

This page last updated: 04/09/2007
Metadata created using Minnesota Geographic Metadata Guidelines


Metadata Summary

Originator U.S. Geological Survey
Abstract A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) topographic map. The scanned image includes all map collar information. The image inside the map neatline is georeferenced to the surface of the Earth using the UTM Zone and datum of the original map (most Minnesota DRGs are NAD27). The DRG can be used to collect, review, and revise other digital data, especially digital line graphs (DLG). When the DRG is combined with other digital products, such as digital orthophoto quadrangles (DOQ) or digital elevation models (DEM), the resulting image provides additional visual information for the extraction and revision of base cartographic information.
Browse Graphic View a sample of the data.
Time Period of Content Date
Currentness Reference Ground condition on the date of field checking or source aerial photographic materials as documented in the DRG collar information. Several dates appear on published USGS quads. The most prominent, and most widely referenced, is printed on the lower right corner of the map. This is usually the year the map was published or revised. In the smaller print along the bottom of the map are other dates for the year of field checking, year of photography, year of survey, or other dates for important work on the map. These dates can be same as the year of publication or up to several years earlier.
Access Constraints None
Use Constraints None. Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from these data.
Distributor Organization USGS Earth Science Information Center
Ordering Instructions USGS distributes DRGs on Compact Disc-Recordable (CD-R) or via FTP. DRG orders are filled on demand. There is a base charge ($45.00 per order for CD or $30.00 per order for FTP), plus $5.00 handling fee, plus $1.00 for each DRG quadrangle purchased. Sale of DRGs in fixed 1-degree block CDs was discontinued on October 1, 1998. The current policy allows any combination of quadrangles to be ordered.

For information on ordering DRG's, contact any Earth Science Information Center (see Distributor Contact for the Rolla Missouri ESIC) or call 1-888-ASK-USGS, toll free. Also check the USGS website: http://topomaps.usgs.gov/drg/

A number of the DRGs along the Mississippi River, including areas within Minnesota as well as Wisconsin, Iowa, Illinois and Missouri, are available online at no charge from the Upper Midwest Environmental Sciences Center website: http://www.umesc.usgs.gov/data_library/maps_quads_figs/drg.html

1:100,000-scale DRGs may be viewed at: http://terraserver.microsoft.com
Online Linkage none available

Full Metadata

Digital Raster Graphics (DRG), 1:24,000 for Minnesota

Go to Section:
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

 
Section 1 Identification Information   Top of page
Originator U.S. Geological Survey
Title Digital Raster Graphics (DRG), 1:24,000 for Minnesota
Abstract A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) topographic map. The scanned image includes all map collar information. The image inside the map neatline is georeferenced to the surface of the Earth using the UTM Zone and datum of the original map (most Minnesota DRGs are NAD27). The DRG can be used to collect, review, and revise other digital data, especially digital line graphs (DLG). When the DRG is combined with other digital products, such as digital orthophoto quadrangles (DOQ) or digital elevation models (DEM), the resulting image provides additional visual information for the extraction and revision of base cartographic information.
Purpose The DRG is used for validating digital line graphs (DLGs) and for DLG data collection and revision. The DRG can help assess the completeness of digital data from other mapping agencies. It can also be used to produce hybrid products. These include combined DRGs and DOQs for revising and collecting digital data, DRGs and DEMs for creating shaded-relief DRGs, and combinations of DRG, DOQ, and DLG data. Although a standard DRG is an effective mapping tool, its full potential for digital production is realized in combination with other digital data.
Time Period of Content Date
Currentness Reference Ground condition on the date of field checking or source aerial photographic materials as documented in the DRG collar information. Several dates appear on published USGS quads. The most prominent, and most widely referenced, is printed on the lower right corner of the map. This is usually the year the map was published or revised. In the smaller print along the bottom of the map are other dates for the year of field checking, year of photography, year of survey, or other dates for important work on the map. These dates can be same as the year of publication or up to several years earlier.
Progress Complete
Maintenance and Update Frequency Irregular
Spatial Extent of Data Minnesota
Bounding Coordinates -97.25
-89.50
49.50
43.50
Place Keywords Minnesota
Theme Keywords imageryBaseMaps,EarthCover, digital raster graphic, DRG, topographic map
Theme Keyword Thesaurus ISO 19115 Topic Category
Access Constraints None
Use Constraints None. Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from these data.
Contact Person Information ,
USGS Earth Science Information Center
1400 Independence Road, MS 231
Rolla, MO 65401-2602
Phone: 573-308-3500
FAX: 573-308-3615
E-mail: esic@mcmcmail.er.usgs.gov
Browse Graphic View a sample of the data.
Browse Graphic File Description Browse graphic on USGS site shows Eastford, Connecticut.
Associated Data Sets 1. For Minnesota quads only, USGS Digital Raster Graphics: 1:24,000-scale, 'clipped' version created by the Minnesota Department of Natural Resources. DNR removed the collar information from the original USGS 1:24,000-scale DRGs and standardized on UTM Zone 15, NAD83 datum. For more information, see http://www.lmic.state.mn.us/chouse/metadata/drg24dnr.html or contact the Land Management Information Center (LMIC) at: clearing.house@state.mn.us or (651) 296-1211.

2. USGS Digital Raster Graphics: 1:100,000-scale

3. USGS Digital Raster Graphics: 1:250,000-scale

 
Section 2 Data Quality Information Top of full metadata Top of page
Attribute Accuracy The USGS DRG uses a standard palette to ensure uniform color throughout a particular map series. The RGB (red, green, blue) values for a particular 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.

DRGs are examined to ensure color consistency within a series. Inspections are performed on selected DRGs to ensure that both the order of digital numbers and digital number values are correct. Colors will be checked for color compliance to map series and for major color differences between features on the DRG and similar features on the source map. Color consistency throughout each series is checked by comparing a DRG to its neighboring quadrangles whenever possible.
Logical Consistency The USGS DRG is 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.
Completeness Image completeness is checked by visually inspecting a sampling of DRGs. Each selected DRG will be examined for gaps (missing data) in the main body of the map, the map collar, the overedge areas, and any insets.

Data completeness for DRG files reflect content of the source graphic. Features may have been eliminated or generalized on the source graphic due to scale and legibility constraints. For information on collection and inclusion criteria, see U.S. Geological Survey, 1994, Standards for 1:24,000-Scale Digital Line Graphs and Quadrangle Maps: National Mapping Program Technical Instructions and U.S. Geological Survey, 1994, Standards for Digital Line Graphs: National Mapping Program Technical Instructions.
Horizontal Positional Accuracy A random sampling of DRGs will be accuracy tested. The accuracy test will be performed by comparing the positions of UTM grid intersections on the source graphic against the corresponding location on the digital image. A visual inspection will determine whether those coordinates fall within the pixels that define a grid tick.

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 percent 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 that area of the DRG that falls within the neatline of the source map (excluding inset areas). Overedge areas falling outside the transformation boundary area (the map neatline), can exhibit anomalies or discrepancies. These anomalies also will 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.
Vertical Positional Accuracy In the DRG, the vertical positional accuracy is referenced in the DRG collar.
Lineage Data Source:
The source for Minnesota DRGs are the standard 1:24,000-scale quadrangle format USGS topographic maps as described in the Federal Geographic Data Committee Manual of Federal Geographic Data Products. The standard area of coverage of a DRG is the entire area printed on a USGS standard series topographic map including the map collar, any overedge areas, and insets.

USGS Processing Steps:
Production of a DRG begins with the scanning of a paper 7.5-minute topographic map on a high-resolution scanner. Scanning resolutions range from 500-1,000 dpi with an output file of 160-300 MB in size. Removal of screens (descreening) and color quantization to reduce the number of colors also takes place during the scanning phase.

The raw scan file is then transformed and georeferenced using UTM coordinates of the sixteen 2.5-minute grid ticks, which are obtained using the in-house produced program COORDAT and stored in a ground control file. Those sixteen 2.5-minute ticks are interactively visited and assigned their respective UTM coordinates. The USGS program XSHAPES4 then performs a piecewise linear rubber sheet transformation.

An output resolution of 2.4 meters (8.2 feet) is chosen to resample the file to 250 dpi. The image file is converted to a TIFF 6.0 image and further reduced by converting the file to a run length encoded PackBits compression (type 32773).

The color palette of the compressed DRG is then standardized by replacing the original RGB values assigned during the scanning process with standard RGB value combinations using the in-house produced TIFFREMAP program.

Prior to archiving, the DRG undergoes the following quality assurance procedures:

1. The color index values of each DRG are checked to ensure the RGB combinations are consistent with the standardized color palette.

2. All DRG files are inspected to ensure that they are geometrically consistent with normal map presentation.

3. Selected DRG's are checked to ensure that data elements in the DRG metadata file correspond to the map collar information and to the information in the associated image file.

4. Selected DRG's are checked for georeferencing accuracy by comparing the book value of latitude and longitude tick marks with corresponding tick intersections in the DRG image.

5. Transformations are checked on selected DRG's by comparing the positions of well defined points, such as UTM grid intersections in the graphic product, with the corresponding image points in the DRG.

USGS DRG production specifications are available on request from the National Mapping Division and Mid-Continent Mapping Center by contacting the U.S. Geological Survey (see Section 6 for Distributor Contact).
Source Scale Denominator 24000
 
Section 3 Spatial Data Organization Information Top of full metadata Top of page
Native Data Set Environment
Geographic Reference for Tabular Data
Spatial Object Type Raster
Vendor Specific Object Types Cell
Tiling Scheme 7.5-minute quadrangle (1:24,000-scale)
 
Section 4 Spatial Reference Information Top of full metadata Top of page
Horizontal Coordinate Scheme UTM
Ellipsoid Clarke 1866
Horizontal Datum NAD27
Horizontal Units Meters
Distance Resolution Unknown
Altitude Datum Not applicable
Altitude Units Not applicable
Depth Datum Not applicable
Depth Units Not applicable
UTM Zone Number 14, 15, 16
Coordinate Offsets or Adjustments None
 
Section 5 Entity and Attribute Information Top of full metadata Top of page
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.

Digital Number, Color, Red Green Blue Values

0 Black 0 0 0
1 White 255 255 255
2 Blue 0 151 164
3 Red 203 0 23
4 Brown 131 66 37
5 Green 201 234 157
6 Purple 137 51 128
7 Yellow 255 234 0
8 Light Blue 167 226 226
9 Light Red 255 184 184
10 Light Purple 218 179 214
11 Light Grey 209 209 209
12 Light Brown 207 164 142
Entity and Attribute Detailed Citation Standards for Digital Raster Graphics. Download documents from:
http://rmmcweb.cr.usgs.gov/public/nmpstds/drgstds.html
 
Section 6 Distribution Information Top of full metadata Top of page
Publisher U.S. Geological Survey
Publication Date Unknown
Contact Person Information

USGS Earth Science Information Center
1400 Independence Road, MS 231
Rolla, MO 65401-2602
Phone: 573-308-3500
FAX: 573-308-3615
E-mail: esic@mcmcmail.er.usgs.gov
Distributor's Data Set Identifier drg_24k
Distribution Liability 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 regarding the use of the data on any other system, nor does the act of distribution constitute any such warranty. The USGS will warrant the delivery of this product in computer-readable format and will offer appropriate adjustment of credit when the product is determined unreadable by correctly adjusted computer input peripherals, or when the physical medium is delivered in damaged condition. Requests for adjustment of credit must be made within 90 days from the date of this shipment from the ordering site.
Transfer Format Name GeoTIFF
Transfer Format Version Number 6.0
Transfer Size Approximately 2 - 10 megabytes per file (unzipped).
Ordering Instructions USGS distributes DRGs on Compact Disc-Recordable (CD-R) or via FTP. DRG orders are filled on demand. There is a base charge ($45.00 per order for CD or $30.00 per order for FTP), plus $5.00 handling fee, plus $1.00 for each DRG quadrangle purchased. Sale of DRGs in fixed 1-degree block CDs was discontinued on October 1, 1998. The current policy allows any combination of quadrangles to be ordered.

For information on ordering DRG's, contact any Earth Science Information Center (see Distributor Contact for the Rolla Missouri ESIC) or call 1-888-ASK-USGS, toll free. Also check the USGS website: http://topomaps.usgs.gov/drg/

A number of the DRGs along the Mississippi River, including areas within Minnesota as well as Wisconsin, Iowa, Illinois and Missouri, are available online at no charge from the Upper Midwest Environmental Sciences Center website: http://www.umesc.usgs.gov/data_library/maps_quads_figs/drg.html

1:100,000-scale DRGs may be viewed at: http://terraserver.microsoft.com
Online Linkage none available
 
Section 7 Metadata Reference Information Top of full metadata Top of page
Metadata Date 04/09/2007
Contact Person Information Nancy Rader, GIS Data Coordination Specialist
Minnesota Land Management Information Center (LMIC)
658 Cedar Street, Room 300
St. Paul, MN 55155
Phone: 651-201-2489
FAX: 651-296-3698
E-mail: clearing.house@state.mn.us
Metadata Standard Name Minnesota Geographic Metadata Guidelines
Metadata Standard Version 1.2
Metadata Standard Online Linkage http://www.lmic.state.mn.us/gc/stds/metadata.htm


This page last updated: 04/09/2007