File: DRG_STD.TXT September 26, 1995 ************************************************************************** National Mapping Program Technical Instructions Standards for Digital Raster Graphics Part 1 GENERAL ************************************************************************** 1.1 DEFINITION The term "digital raster graphic" (DRG) is used throughout this document to refer to a raster image of a scanned U.S. Geological Survey (USGS) topographic map. The DRG is a product of the USGS. 1.2 OBJECTIVES The USGS is designated the lead Federal agency for the collection and distribution of digital cartographic data. This document contains general information pertaining to the collection, processing, and quality control of DRG data. Where applicable, USGS DRG production specifications are presented for clarification purposes. The USGS intends to collect, revise, and perform quality control processes on other digital base cartographic data using DRG's, e.g. checking the registration of other digital product's by overlaying them on top a DRG. This standard outlines these DRG requirements. This standard highlights those key dependencies involved in the production of USGS DRG's. The technology to produce a DRG-like product is widespread and products similar to DRG's are available from a variety of Federal, State, and private industry producers. While these DRG-like products do not necessarily meet USGS specifications, they may be very close to the USGS standard and, whenever possible, the USGS intends to take advantage of the availability of these products. Therefore, the option exists to consider comparable products for inclusion in the USGS DRG program. However, it is important to note that product uniformity, production expediency, and quality control considerations will determine whether or not the USGS will exercise this option. The USGS plans to produce the majority of DRG data or acquire similar raster products through cooperative agreements with private industry and other Federal, State, and local agencies. Under Joint Funding Agreements (JFA), the USGS and its contractors will produce the DRG to USGS specifications. However, the USGS recognizes that some agencies and producers have existing data or plan to produce digital data that meet or approximate the USGS product specifications. In such cases, other cooperative agreements allow the USGS to offer some remittance for the rights to those data. Cooperative agreements such as the Innovative Partnership program are contingent on product inspection and approval by the USGS. 1.3 PRODUCT DESCRIPTION DRG's retain the geometric and visual qualities of the source maps in all respects with these exceptions: (1) DRG's are georeferenced to Universal Transverse Mercator (UTM) ground coordinates and may exhibit distortions in the collar, inset, and overedge areas, and (2) the colors of the DRG can differ slightly from the original printed map. DRG's share many characteristics with raster graphic products, including: o Their sources are printed maps, map separates, color composites, or any other reasonably stable map material. Some products are available as raster images of the map separates. o Their areal extent may be the entire printed source extent including the map collar, legend, and any overedge or insets. Pertinent source and map information are contained in the collar and legend, which can be unobtainable if the raster graphic is cropped at the neatlines. o Scanning and output resolutions may vary. Major factors in determining scanning resolution are the product's intended use, scanner capability, and the quality and detail of the source map. File size or the desire to create a workable file size can be a determining factor for output resolution. o DRG's and comparable products are generally cast and georeferenced on common, widely used projections and coordinate systems. The DRG is cast on the UTM projection and coordinate system, while many raster products created by State and local agencies employ their respective State plane coordinate system. Georeferencing allows the user the ability to fit other digital data to the DRG to perform any number of geospatial applications. o DRG's and comparable products should meet the horizontal accuracy standard of its source. Accuracy measurements or a description of how the image was accuracy tested should accompany the data. The USGS product will meet the National Map Accuracy Standard (NMAS) for the source map scale. o DRG's and other raster products use a color palette to maintain color consistency across images within a given map series. This allows for uniform and visually consistent images throughout a series for the purpose of mosaicking, feature identification, and multiple image viewing. o DRG's, conform to widely recognized industry standard file formats. o Metadata, data about the image, accompany the product. Metadata provide identification, georeferencing, accuracy, and source lineage data about the image. The DRG is accompanied by an Federal Geographic Data Committee (FGDC) compliant metadata file. At the USGS, DRG's serve a variety of purposes: from use as backgrounds for other data in a GIS to a source for collecting or revising USGS base cartographic data. The DRG shows potential as a tool for validating and assessing other non-USGS digital data. The DRG can be combined with digital orthophoto quadrangle (DOQ), digital elevation model (DEM), and digital line graph (DLG) data, or combinations of these data can create several "hybrid" products, each with its own unique applications. DRG prototypes have been used as "browse images" on in-house data management systems and can serve similarly in production systems and sales data bases. Although hard-copy output of the DRG is not now being considered, in the future, the DRG or its hybrids could be available on demand as one-of-a-kind custom products or as a means to meet the demands for maps that are out of stock. Although a DRG can be made from any USGS map, the DRG program is oriented toward the production of DRG's from 1:24,000-, 1:25,000-, 1:63,360-, 1:100,000-and 1:250,000-scale USGS topographic maps to be used in the validation and revision of DLG data. 1.4 USGS DRG PROCESS DESCRIPTION The production procedures, instrumentation, hardware, and software used in the collection of standard DRG products vary depending on systems used at the contractor, cooperator, or USGS production sites. As the majority of DRG data sets are acquired through government contract, the following describes the general processes used in the production of standard DRG data sets. - A paper topographic map is scanned on a high-resolution scanner. - Screens are removed (descreening) and colors quantized to reduce the number of colors in the raw scan file. - The raw scan file is transformed and georeferenced using UTM coordinates. - The output file is reduced in size via resampling to 250 dot-per-inch (dpi), converting to a TIFF, and compressed. - Prior to archiving, the DRG undergoes a series of quality assurance checks. A more detailed explanation of the processes used in the construction of a DRG may be found in Data Quality Information Section of the Metadata Template (Appendix 2-A) under the 2.5.2.1 Process Description element. *************************************************************************** Part 2 SPECIFICATIONS *************************************************************************** 2.1 DEFINITIONS: Color palette - a look-up table that describes how data values map to colors. Compression - a method of encoding data to optimize storage or speed transmission by reducing the number of bits required to describe an image. Descreening - the process of removing the lithographic screen patterns used to create different shades or hues of a color on a printed map from a digital copy of that map. Georeference - to establish the relationship between an image (row, column) coordinate system and a map (x,y) coordinate system. Metadata - data about the content, quality, condition, and other characteristics of data. Quantization - the process of converting from continuous values of information to a finite number of discrete values. Rubber sheeting - a process that geometrically adjusts map features to "force" a digital map to fit a designated base. It is called rubber sheeting because the map is mathematically stretched to fit the base, given a set of known coordinate values whose locations are defined on both the base map and the map to be rubber sheeted. The process uses mathematical operations to minimize distortion (See transformation). Transformation - the conversion of coordinates from one coordinate system to another. For the purpose of this standard, the conversion of x- and y- image coordinates of a scanner to X- and Y-coordinates of the UTM. 2.2 IMAGE FORMAT USGS DRG's employ an 8-bit PackBits compressed Tagged Image File Format (TIFF), palette color format. DRG's use GeoTIFF tag (the field identifier) specifications to describe the georeferencing or geocoding of the DRG raster images. (Refer to section 2.6, Projections and Georeferencing). The TIFF palette color format is similar to a gray scale image in that a single value is assigned to a pixel. However, in the palette color format, that value assigned to a pixel is used as an index to an RGB look-up table (Refer to Section 2.9, Color Standardization). The most recent revision of TIFF specifications is available via World Wide Web at: http//mcmcweb.cr.usgs.gov/ For other TIFF inquiries, e-mail: esic@mcdgs01.cr.usgs.gov The orientation of data is by lines (rows) and samples (columns). Line and sample 1,1 will be in the upper left-hand corner of the collar area of the DRG; not the northwest neatline corner of the mapped area. Each line contains a series of pixels ordered from west to east. The order of the lines is from north to south. When displayed on a computer graphics terminal, projection grid north is at the top. However, the image is displayed in its proper UTM configuration and, therefore, may not be parallel with the outer edges of the DRG collar (the area of the map that lies outside the neatlines). The collar area of the DRG may be distorted depending on how far the DRG lies from the central meridian of its respective UTM; the closer to the central meridian, the less distortion in the collar area. The distortions are due to georeferencing the map image area (the area within the neatlines) to the UTM while the collar area remains aligned to geographic north. Stretching occurs and is manifested in distorted collar text. 2.3 SOURCES The source for DRG's are the standard quadrangle format USGS topographic maps as described in the Federal Geographic Data Committee "Manual of Federal Geographic Data Products." They include 1:20,000-, 1:24,000-, 1:25,000-, 1:30,000, 1:63,360-, 1:100,000- and 1:250,000-scale topographic maps. Included in the 1:24,000- and 1:25,000-scale series are provisional (P) and color orthophotomaps. Paper maps, composite color proofs, or map separates from those map series can be used as the source for scanning the image. The USGS intends to scan paper maps to produce DRG's whenever possible. By scanning paper maps, as opposed to color composites or map separates, a considerable cost savings is realized in labor, materials, and scanning time. Concerns over distortions due to paper shrinkage and stretching are minimized by using high-quality printing materials and unfolded maps whenever possible. Although map separates may be employed as a scanning source, the separates must be combined into a single DRG file. 2.4 COVERAGE 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. These standard series maps include: o 7.5-minute map series: Conterminous United States, Hawaii, and limited areas of Alaska at 1:24,000 and 1:25,000 scale. o 7.5- by 15-minute map series: Covers limited areas of the conterminous United States at 1:25,000 scale. o Pacific Island map series at 1:20,000, 1:24,000, and 1:25,000 scale. o Puerto Rico and the Virgin Islands at 1:20,000 scale. Culebra, its adjacent islands, and the Island of Vieques at 1:30,000 scale. o Alaska at 1:63,360 scale. o 30- by 60-minute map series: Conterminous United States and Hawaii at 1:100,000 scale. o 1- by 2-degree map series: United States at 1:250,000 scale. 2.5 DRG RESOLUTION 2.5.1 Scan resolution DRG's will be scanned on a quality micro densitometer at 250 dpi and finer. The USGS will produce DRG's scanned at a resolution of 500 dpi. Scanner limitations, large image file sizes, and processing times are considerations in the choice of a scanning resolution. The USGS has concluded that its production capabilities and requirements for digital revision and validation are adequately met by DRG's scanned at 500 dpi. However, other requirements may dictate finer scanning resolutions; e.g. hard-copy needs and image extraction. A 7.5-minute topographic map scanned at 1,000 dpi has a ground pixel resolution of approximately 2 feet, 4 feet at 500 dpi and 7.9 feet at 250 dpi. 2.5.2 Output resolution The resolution of the finished DRG will be 250 dpi. 2.6 PROJECTIONS AND GEOREFERENCING The USGS DRG is cast on the UTM projection. This is consistent with other USGS digital data series cast on the UTM projection. However, in some instances, this makes the image inconsistent with the projection statement on the source map collar. For example, the legend on the USGS 7.5-minute topographic map of Richmond, Virginia, reads, "Projection and 10,000-foot grid ticks: Virginia Coordinate system, South zone (Lambert conformal conic)." The datum of the published source map is preserved in the DRG. The majority of 7.5-minute topographic maps are cast on the North American Datum of 1927 (NAD27). DRG's produced by the USGS are georeferenced to fit the computed UTM values of the latitude and longitude ticks on each image. Included in those ticks are the corners of the map neatline. For the 1:24,000- and 1:25,000- scale 7.5-minute series maps, the sixteen 2.5-minute ticks are used; the twenty-eight 2.5-minute ticks for the 1:25,000-scale, 7.5-minute by 15-minute series; the fifteen 15-minute ticks for the 1:100,000-scale series; and the forty-five 15-minute ticks for the 1:250,000-scale map series. The number and spacing of ticks for the 1:63,360-scale Alaska series quadrangles vary depending on the position of the quadrangle along the longitudinal axis. All UTM values must be in meters. Map inset areas will not undergo separate georeferencing procedures. USGS DRG's employ GeoTIFF specifications that define a set of TIFF tags to describe all "cartographic" information associated with TIFF images originating from the scanned source. Its purpose is to allow a means for tying a raster image to a known model space or map projection, and for describing those projections. The most recent revision of the GeoTIFF specification is available via World Wide Web at: http//mcmcweb.cr.usgs.gov/ For other GeoTIFF inquiries, e-mail: esic@mcdgs01.cr.usgs.gov 2.7 ACCURACY DRG's will meet the horizontal accuracy of the source maps. USGS printed maps meet National Map Accuracy Standards (NMAS) for particular scales. For the 7.5-minute 1:24,000-scale series, NMAS specify that 90 percent of the well-defined points tested must fall within 40 feet (1/50 inch). For DRG's 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 fall outside the transformation boundary area (the map neatline). As a result, areas outside the neatline and outside the control point extent can exhibit anomalies or discrepancies. These anomalies also will appear in the map inset areas and in the map collar. 2.8 COLOR STANDARDIZATION Although only six inks are employed on a USGS topographic map, screen printing processes can create more than six defined colors. USGS DRG's will employ a color palette or look-up table consisting of 13 colors depending on the map series and whether or not the scanned image is descreened. The digital number is defined in the palette by three numbers: one each for red, green, and blue and each separately defined as a value from 0-255. Table 2-1 describes the DRG color palette. The colors defined in the color look-up table are chosen to represent as closely as possible the colors of the printed map within a map series. However, it is likely that the DRG will not match precisely the colors of it's printed counterpart. An example of a specific color variation on DRG's applies to the display of bathymetric depths, which are printed on some paper maps as different shades of blue--the deeper the depth, the bluer the color. The DRG will contain only two blues, dark blue for shorelines and light blue for open water bodies, to describe all open water blues on a given map. Table 2-1 USGS DRG Color Palette ------------------------------------------------------------- Digital Number Color Red Green Blue ------------------------------------------------------------- 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 ------------------------------------------------------------- 2.9 DESCREENING, QUANTIZING, AND NOISE FILTERING Removal of lithographic screen patterns is desirable but is not required. Lithographic screen patterns can be retained until reliable automated methods are developed to electronically remove them without impairing the visual acuity of the underlying features. 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 the 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: the quality of the source, use of screens and patterns on the litho, and unevenness of the ink due to saturation and absorption. Discontinuities or breaks in line features are apparent and due to the effects of scanning, 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. Until automated or easy and efficient editing procedures for cleaning this noise that do not adversely affect the geometric and visual integrity of the image are developed, no attempt will be made to clean the noise from a DRG. 2.10 IMAGE MOSAICKING Edge matching or mosaicking of a DRG to its neighboring DRG's is not a requirement. 2.11 DATA QUALITY 2.11.1 Radiometric Verification DRG's are examined to ensure completeness and color consistency within a series. Image completeness is checked via visual inspection of a sampling of DRG's. Inspections are performed on selected DRG's 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. DRG's are checked for color consistency throughout each series by comparing a DRG to its neighboring quadrangles whenever possible. 2.11.2 Accuracy Verification Visual verification will be performed for image completeness, to ensure that no gaps exist in either the image area, map collar, overedge areas, or insets. The accuracy of the DRG will be tested using established or documented testing algorithms. DRG's are accuracy tested by comparing the positions of UTM grid intersections on the source graphic against the corresponding location on the digital image and visually ascertaining whether those coordinates fall within the black pixels that define a grid tick. No accuracy value will be recorded and only selected DRG's will be accuracy tested. No separate georeferencing will be performed on areas within an inset, nor will insets be tested or assumed to meet accuracy standards. 2.12 METADATA DRG's will be accompanied by metadata (data about the image) containing a wide range of information about the image data to assist the users and potential users in determining the availability, fitness, means of accessing, and transfer of the data. Metadata is also important as a means for establishing quality control. Federal agencies have a metadata requirement mandated by Executive Order (EO) 12906 (April 11, 1994). EO 12906 established the National Spatial Data Infrastructure and adopted the Federal Geographic Data Committee's (FGDC) "Content Standard for Digital Geospatial Metadata." This standard provides a consistent approach and format for the description of data characteristics. Every DRG will have an associated metadata file that will comply to those standards. The template shown in Appendix 2-A is an example of the metadata required by the FGDC standard. Note that, when applicable, the element value is shown. These values are considered "generic"; they are germane to an entire DRG series and are repeated in every metadata file of each DRG in that series. File-specific values are associated with a particular image and can only appear once within a map-scale series. The entries for file- specific data presented in the template contain domain descriptions from the "Content Standards for Digital Geospatial Metadata" and the source for the data that will be used to populate that element value. Each DRG will be accompanied by a metadata file containing the generic, data-series information, as well as the file specific metadata. Copies of the "Content Standards for Digital Geospatial Metadata" (meta6894.*) in PostScript, ASCII text, and WordPerfect formats are available via anonymous FTP at: ftp://fgdc.er.usgs.gov/pub/metadata/ ************************************************************************** References Aldus Corporation, 1992, TIFF Revision 6.0 (June 3): Aldus Corporation, Seattle, Wash. Department of Commerce, 1977, Countries, Dependencies, Areas of Special Sovereignty, and their Principal Administrative Divisions (Federal Information Processing Standard 10-3): National Institute of Standards and Technology. Department of Commerce, 1987, Codes for the Identification of the States, The District of Columbia and the Outlying Areas of the United States, and Associated Areas (Federal Information Processing Standard 5-2): National Institute of Standards and Technology. Federal Geographic Data Committee, 1992, Manual of Federal Geographic Data Products (September): Washington, D.C. Federal Geographic Data Committee, 1994, Content Standards for Digital Geospatial Metadata (June 8): Washington, D.C. Fortner, B., 1992, The Data Handbook--A Guide to Understanding and Visualization of Technical Data: Champaign, Ill., Spyglass. Jensen, J., 1986, Introductory Digital Image Processing: Englewood Cliffs, N.J., Prentice-Hall. U.S. Geological Survey, 1994, Standards for 1:24,000-Scale Digital Line Graphs and Quadrangle Maps: National Mapping Program Technical Instructions. U.S. Geological Survey, 1994, Standards for Digital line Graphs: National Mapping Program Technical Instructions. *************************************************************************** APPENDIX 2-A Digital Raster Graphics - Metadata Template *************************************************************************** INFORMATION ABOUT THE TEMPLATE 1. Metadata elements are in uppercase followed by a value. 2. Numbers preceding data elements refer to section numbers in the "Content Standards for Digital Geospatial Metadata", June 8, 1994. 3. Section numbers preceded by an asterisk (*) indicate file specific elements. These are followed by the element description from the "Content Standards for Digital Geospatial Metadata" and bracketed comments where applicable. 4. Element values specified by the "Content Standards for Digital Geospatial Metadata" are prefaced and followed by double quotation marks. --Identification Information-- -Citation- 8.1 ORIGINATOR: USGS [Some DRG's may originate from mapping agencies or programs other than the USGS. In such a case, the name of the organization or individual that developed the data set would be placed here.] *8.2 PUBLICATION DATE: The date when the data set is published or otherwise made available for release. [A single date is used to populate three separate DRG metadata elements. They are: 1. the Identification Information/Publication Date (8.2). The FGDC definition for element Publication Date is the "date when the data set is published or otherwise made available." That date is the date the last DRG production step occurs, which is the completion of the metadata file. 2. the Publication Information/Process Date (2.5.2.3). The element Process Date is described as the "date when the event was completed" or, in the case of DRG's, the date when the last DRG production step, processing the metadata file, was completed. 3. the Metadata Reference Information/Metadata Date (7.1). The date the metadata were created is the same as the date of the last production step (Process Date), and when the data becomes available (Publication Date).] *8.4 TITLE: The name by which the data set is known. [The map name as designated by the Topographic Map Names Data Base. Note that the source map for the DRG can be an older, unrevised map and have a different name than the DRG.] 8.6 GEOSPATIAL DATA PRESENTATION FORM: "map" -Publication Information- 8.8.1 PUBLICATION PLACE: Reston, VA 8.8.2 PUBLISHER: USGS -Description- 1.2.1 ABSTRACT: A DRG is a raster image of a scanned USGS topographic map including the collar information, georeferenced to the UTM grid. 1.2.2 PURPOSE: A DRG is useful as a source or background layer in a GIS, as a means to perform quality assurance on other digital products, and as a source for the collection and revision of DLG data. DRG's can also be merged with other digital data, e.g. DEM's or DOQ's, to produce a hybrid digital file. *1.2.3 SUPPLEMENTAL INFORMATION: Other descriptive information about the data set. [The USGS will place the UTM metric coordinates of pixel 1,1 in this element.] -Time period of content- Single Date/Time *9.1.1 CALENDAR DATE: The year (and optionally month, or month and day). The latest date found beneath the map title on the lower right hand side of the source map populates the Calendar Date element. 1.3.1 CURRENTNESS REFERENCE: "Ground Condition" -Status- 1.4.1 PROGRESS: "Complete" 1.4.2 MAINTENANCE AND UPDATE FREQUENCY: "Irregular" -Spatial Domain- Bounding Coordinates *1.5.1.1 WEST BOUNDING COORDINATE: Western-most coordinate of the limit of coverage expressed in longitude [-]. *1.5.1.2 EAST BOUNDING COORDINATE: Eastern-most coordinate of the limit of coverage expressed in longitude [-]. *1.5.1.3 NORTH BOUNDING COORDINATE: Northern-most coordinate of the limit of coverage expressed in latitude. *1.5.1.4 SOUTH BOUNDING COORDINATE: Southern-most coordinate of the limit of coverage expressed in latitude. -Keywords- Theme 1.6.1.1 THEME KEYWORD THESAURUS: "None" 1.6.1.2 THEME KEYWORD: digital raster graphic 1.6.1.2 THEME KEYWORD: DRG 1.6.1.2 THEME KEYWORD: topographic map Place 1.6.2.1 PLACE KEYWORD THESAURUS: Department of Commerce, 1977, Countries, Dependencies, Areas of Special Sovereignty, and their Principal Administrative Divisions (Federal Information Processing Standard 10-3): Washington, Department of Commerce, National Institute of Standards and Technology. *1.6.2.2 PLACE KEYWORD: The geographic name of a location covered by a data set. [The United States (and Mexico or Canada).] 1.6.2.1 PLACE KEYWORD THESAURUS: Department of Commerce, 1987, Codes for the Identification of the States, The District of Columbia and the Outlying Areas Of The United States, and Associated Areas (Federal Information Processing Standard 5-2): Washington, Department of Commerce, National Institute of Standards and Technology. *1.6.2.2 PLACE KEYWORD: The geographic name of a location covered by a data set. [STATE1] *1.6.2.2 PLACE KEYWORD: The geographic name of a location covered by a data set. [STATE2] 1.7 ACCESS CONSTRAINTS: "None" 1.8 USE CONSTRAINTS: Acknowledgment of the USGS would be appreciated in products derived from these data. *1.11 DATA SET CREDIT: Recognition of those who contributed to the data set. [States or agencies that contribute to the production of DRG's can receive a credit here.] --Data Quality Information-- -Attribute Accuracy- 2.1 ATTRIBUTE ACCURACY REPORT: The DRG is an 8-bit color image that employs a color palette to ensure uniform colors throughout a particular DRG series. All DRG's within a series must have the same RGB value. 2.2 LOGICAL CONSISTENCY REPORT: Not Applicable 2.3 COMPLETENESS REPORT: The DRG is a faithfully reproduced digital image of the original source map. Some differences may be detected between the source graphic used for scanning and the DRG due to the RGB values assigned that particular color. The intent is to recreate those colors as near as possible. 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. -Positional Accuracy- Horizontal Positional Accuracy 2.4.1.1 HORIZONTAL POSITIONAL ACCURACY REPORT: Although the datum of the published map is retained to be consistent with other USGS digital data, this image is cast on the UTM and may be INCONSISTENT with the credit note on the image collar. Vertical Positional Accuracy 2.4.2.2 VERTICAL POSITIONAL ACCURACY REPORT: Refer to the DRG collar for information about vertical positional accuracy. -Lineage- Source Information Source Citation 2.5.1.5 SOURCE CITATION ABBREVIATION: map1 8.1 ORIGINATOR: USGS *8.2 PUBLICATION DATE: The date when the data set is published or otherwise made available for release. [The latest date beneath the map title.] *8.4 TITLE: The name by which the data set is known. [Source map name.] 8.6 GEOSPATIAL DATA PRESENTATION FORM: "map" --Publication Information-- 8.8.1 PUBLICATION PLACE: Reston, VA 8.8.2 PUBLISHER: USGS *2.5.1.2 SOURCE SCALE DENOMINATOR: The denominator of the representative fraction on a map (for example, on a 1:24,000-scale map, the Source Scale Denominator is 24000). 2.5.1.3 TYPE OF SOURCE MEDIA: "paper" -Source Time Period of Content- Single Date/Time *9.1.1 CALENDAR_DATE: The year (and optionally month, or month and day). [The date found beneath the map title on the lower right hand side of the source map if *only* a single date is present. If two or more dates exist beneath the map title then multiple dates are listed (see following text in double brackets). [[If multiple dates are shown beneath the map title of the source map the following dates are required: *9.1.1 CALENDAR_DATE: The year (and optionally month, or month and day). [The black map date.] 2.5.1.4.1 SOURCE CURRENTNESS REFERENCE: "ground condition" *9.1.1 CALENDAR_DATE: The year (and optionally month, or month and day). [The latest revision date.] 2.5.1.4.1 SOURCE CURRENTNESS REFERENCE: "ground condition" *9.1.1 CALENDAR_DATE: The year (and optionally month, or month and day). [The photo inspection date if minor revision or reprint.] 2.5.1.4.1 SOURCE CURRENTNESS REFERENCE: "ground condition"]] 2.5.1.4.1 SOURCE CURRENTNESS REFERENCE: "ground condition" 2.5.1.6 SOURCE CONTRIBUTION: The source map is scanned to produce the DRG. -Process Step- 2.5.2.1 PROCESS DESCRIPTION: The production procedures, instrumentation, hardware, and software used in the collection of standard DRG products vary depending on systems used at the contract, cooperator, or USGS production sites. The majority of DRG data sets are acquired through government contract. The process step describes, in general, the process used in the production of standard DRG data sets. 1. Production of a DRG begins with the scanning of a paper 7.5-minute topographic map (map1) on a high-resolution scanner. Scanning resolutions range from 500-1000 dpi with the output file running between 160-300 Mb. 2. Removal of screens (descreening) and color quantization to reduce the number of colors also takes place during the scanning phase. 3. 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. USGS program XSHAPES4 then performs a piecewise linear rubber sheet transformation. 4. An output resolution of 2.4 meters (8.2 feet) is chosen to resample the file to 250 dpi. 5. The image file is converted to a TIFF image and further reduced by converting the file to a run length encoded PackBits compression (type 32773). 6. 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. 7. Prior to archiving the DRG undergoes the following quality assurance procedures: a. The color index values of each DRG are checked to ensure the RGB combinations are consistent with the standardized color palette. b. All DRG files are inspected to ensure that they are geometrically consistent with normal map presentation. c. 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. d. 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. e. 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: Rolla-ESIC U.S. Geological Survey 1400 Independence Rd., MS231 Rolla, MO 65401-2602 Phone (314)341-0851 Facsimile (314)341-9375 E-mail to esic@mcdgs91.cr.usgs.gov World Wide Web: http://mcmcweb.cr.usgs.gov/gdc/ 2.5.2.2 SOURCE USED CITATION ABBREVIATION: The Source Citation Abbreviation of a data set used in the processing step. [map1] *2.5.2.3 PROCESS DATE: The date when the event was completed. [Production date.] --Spatial Data Organization Information-- 3.2 DIRECT SPATIAL REFERENCE METHOD: "Raster" -Raster Object Information- 3.4.1 RASTER OBJECT TYPE: "Pixel" *3.4.2 ROW COUNT: The maximum number of raster objects along the ordinate (y) axis. *3.4.3 COLUMN COUNT: The maximum number of raster objects along the abscissa (x) axis. --Spatial Reference Information-- -Horizontal Coordinate System Definition- Planar 4.1.2.2.1 GRID COORDINATE SYSTEM NAME: "Universal Transverse Mercator" Universal Transverse Mercator (UTM) *4.1.2.2.2.1 UTM ZONE NUMBER: The identifier for the UTM zone. Transverse Mercator 4.1.2.1.2.17 SCALE FACTOR AT CENTRAL MERIDIAN: 0.9996 *4.1.2.1.2.2 LONGITUDE AT CENTRAL MERIDIAN: The line of longitude at the center of a map projection generally used as the basis for constructing the projection. [-] 4.1.2.1.2.3 LATITUDE OF PROJECTION ORIGIN: 0.0 4.1.2.1.2.4 FALSE EASTING: 500000. 4.1.2.1.2.5 FALSE NORTHING: 0.0 --Planar Coordinate Information-- 4.1.2.4.1 PLANAR COORDINATE ENCODING METHOD: "row and column" -Coordinate Representation- *4.1.2.4.2.1 ABSCISSA RESOLUTION: The (nominal) minimum distance between the "x" or column values of two adjacent points expressed in Planar Distance Units of measure. *4.1.2.4.2.2 ORDINATE RESOLUTION: The (nominal) minimum distance between the "y" or row values of two adjacent points, expressed in Planar Distance Units of measure. 4.1.2.4.4 PLANAR DISTANCE UNITS: "meters" -Geodetic Model- *4.1.4.1 HORIZONTAL DATUM NAME: The identification given to the reference system used for defining the coordinates of points. [The datum used is the datum of the DRG source.] *4.1.4.2 ELLIPSOID NAME: The identification given to established representations of the Earth's shape. [The ellipsoid of the DRG source; e.g GRS 1980, Clarke 1866.] *4.1.4.3 SEMI-MAJOR AXIS: Radius of the equatorial axis of the ellipsoid. [GRS 1980 = 6378137, Clarke 1866 = 6378206.4] *4.1.4.4 DENOMINATOR OF FLATTENING RATIO: The denominator of the ratio of the difference between the equatorial and polar radii of the ellipsoid when the numerator is set to 1. [GRS 1980 = 298.257, Clarke 1866 = 294.98] --Entity and Attribute Information-- -Overview Description- 5.2.1 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. USGS DRG Color Palette -------------------------------------------------------- Digital Number Color Red Green Blue -------------------------------------------------------- 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 -------------------------------------------------------- 5.2.2 ENTITY AND ATTRIBUTE DETAIL CITATION: Draft Standards for Digital Raster Graphic. --Distribution Information-- -Distributor- Contact Organization Primary 10.1.2 CONTACT ORGANIZATION: Earth Science Information Center, U.S. Geological Survey Contact Address 10.4.1 ADDRESS TYPE: "mailing address" 10.4.2 ADDRESS: 507 National Center 10.4.3 CITY: Reston 10.4.4 STATE OR PROVINCE: Virginia 10.4.5 POSTAL CODE: 22092 10.5 CONTACT VOICE TELEPHONE: 1 800 USA MAPS 10.5 CONTACT VOICE TELEPHONE: 1 703 648 6045 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 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. -Standard Order Process- Digital Form Digital Transfer Information 6.4.2.1.1 FORMAT NAME: TIFF 6.4.2.1.2 FORMAT VERSION NUMBER: 6.0 6.4.2.1.6 FILE DECOMPRESSION TECHNIQUE: PackBits Digital Transfer Option Offline Options 6.4.2.2.2.1 OFFLINE MEDIA: "CD-ROM" 6.4.2.2.2.3 RECORDING FORMAT: "ISO 9660"; DRG image files with corresponding metadata files. 6.4.3 FEES: For delivery on compact disc, the charge is $32 per CD-ROM --Metadata Reference Information-- *7.1 METADATA DATE: The date that the metadata were created or last updated. Metadata Contact Contact Organization Primary 10.1.2 CONTACT ORGANIZATION: U.S. Geological Survey Contact Address 10.4.1 ADDRESS TYPE: "mailing address" 10.4.2 ADDRESS: 590 National Center 10.4.3 CITY: Reston 10.4.4 STATE OR PROVINCE: Virginia 10.4.5 POSTAL CODE: 22092 10.5 CONTACT VOICE TELEPHONE: 1 703 648 4533 10.8 CONTACT ELECTRONIC MAIL ADDRESS: Copies of this publication are available from anonymous File Transfer Protocol (anonymous FTP); ftp://fgdc.er.usgs.gov/ 7.5 METADATA STANDARD NAME: "Content Standards for Digital Geospatial Metadata" 7.6 METADATA STANDARD VERSION: 19940608