DRG - Digital Raster Graphic, USGS 7.5' Quad Images (full sheet) Teale Data Center, Sacramento, CA 12/15/1998 COVERAGE DESCRIPTION: Digital Raster Graphics are PackBit-compressed tiff images of USGS 7.5 minute quadrangle maps. There are 2,851 images covering the entire state of California. Teale Data Center created the DRGs for California on behalf of USGS. Teale's DRGs differ from those produced by USGS in terms of resolution and projection. BRIEF METHODOLOGY: - Image is scanned at 400 dpi, and colors normalized to 13 RGB values. - Image is converted to Arc Info grid file - Grid file undergoes descreening to eliminate scatter and enhance solid fills in areas such as water bodies and forests. - Grid file is registered to albers projection. - Grid file is converted to .tif image with PackBit compression option. VITAL STATISTICS: Resolution: 400 d.p.i. Projection: Albers Units: Meters 1st Std. Parallel: 34 00 00 (34.0 degrees N) 2nd Std. Parallel: 40 30 00 (40.5 degrees N) Longitude of Origin: -120 00 00 (120.0 degrees W) Latitude of Origin: 00 00 00 (0.0 degrees) False Easting (X shift): 0 False Northing (Y shift): -4,000,000 Datum: NAD 27 Spheroid: Clarke 1866 Source: U.S.G.S. Source Media: Map sheets Source Projection: vary Source Units: Meters Source Scale: 1:24,000, 11 DRGs are 1:25,000 Capture Method: Scanned Conversion Software: ARC/INFO rev. 7.2.1 Data Structure: Raster Size of DRGs: Range 2 - 40 MB, 13 MB on average per image 40 Gigabytes statewide Use limitation: None - public domain data Data Updated: December 1998 There are 64 DRGs in each 1 degree block of longitude and latitute, filling 8 rows and 8 columns. DRG files are named according to USGS 'ocode' designation: example: o35116a7.tif 35 degree of latitude 116 degree of longitude a row (a-h south to north) 7 column (1-8 east to west) Each DRG has an accompanying 'world' file with the same file name, but with a .tfw extension, that contains geo-referencing information: example: o35116a7.tfw 1.52786215012960 pixel size (meters) 0.00000000000000 rotation factor 0.00000000000000 rotation factor -1.52786215012960 pixel size 284543.57694197021192 image min x (meters) (NW -316411.17369714472443 image max y (meters) Corner) The min x and min y coordinates relate to the image itself, and not the latitude longitude values at the map corner. Coordinates are in albers projection. COLORS Colors on the DRGs have been normalized to 13 RGB values: 0 0 0 black 255 255 255 white 91 159 230 dark blue 230 45 30 red 162 96 71 dark brown 210 255 177 green 197 101 197 dark magenta 255 240 0 yellow 202 225 245 light blue 255 202 197 light red 250 202 250 light magenta 230 230 230 light grey 222 167 146 light brown DRG.DBF fields: COL ITEM NAME WDTH OPUT TYP N.DEC 1 OCODE 8 8 C - 9 MAPNAME 30 30 C - 39 MAPNAME25 20 20 C - 59 CD 2 2 C - 61 FILESIZE 8 8 C - 69 MAPSCALE 8 8 C - 77 FORMAT 20 20 C - 97 REF_CODE 25 25 C - 122 YEAR 4 4 C - 126 YRORIGMAP 4 4 C - 130 YRREVISION 4 4 C - 134 YRAIRPHOTO 4 4 C - 138 YRFIELDCK 4 4 C - 142 YRPHTOTOPO 4 4 C - 146 YRREVSOURC 4 4 C - 150 YRPHTOINSP 4 4 C - 154 SOUTH 8 10 F 5 162 NORTH 8 10 F 5 170 EAST 8 10 F 5 178 WEST 8 10 F 5 186 SE_COR_LON 9 9 C - 195 SE_COR_LAT 9 9 C - 204 CONTOURINT 10 10 C - 214 CONINTRMIT 10 10 C - 224 VERT_DATUM 15 15 C - 239 STATE1 2 2 C - 241 STATE2 2 2 C - 243 TYPE 1 1 C - 244 PROJECTION 80 80 C - 324 XNOST 175 175 C - OCODE USGS coding convention for 7.5 X 7.5 minute quads. MAPNAME Name of 7.5 X 7.5 minute quad map MAPNAME25 Name of 7.5 X 15 minute quad map (see note below) CD CD number - index to which CD the image is on FILESIZE Size of tiff image file in megabytes MAPSCALE Scale of scanned map FORMAT Dimension in Minutes of map, N-S X E-W REF_CODE USGS reference code YEAR Most recent year that appears on the map. YRORIGMAP Year of original map YRREVISION Year of map revision YRAIRPHOTO Year of aerial photography used for revision YRFIELDCK Year of field check YRPHTOTOPO Year of aerial photography used for topography base YRREVSOURC Year of source data for revision YRPHTOINSP Year of photo inspection SOUTH Southern extent of map area, decimal degrees NORTH Northern extent of map area, decimal degrees EAST Eastern extent of map area, decimal degrees WEST Western extent of map area, decimal degrees (SOUTH, NORTH, EAST and WEST are used for trimming DRGs to their neatline, or in the case of irregular DRGs, to the outer extent of the map area. SE_COR_LON Longitude at south-east corner, degrees minutes seconds SE_COR_LAT Latitude at south-east corner, degrees minutes seconds CONTOURINT Contour interval CONINTRMIT Intermittant contour interval VERT_DATUM Vertical Datum STATE1 State primarily covered in the image STATE2 State secondarily covered in the image TYPE Type of map, to identify non-standard maps S Standard 7.5 X 7.5 Minute T Tall >7.5 X 7.5 Minute W Wide 7.5 X >7.5 Minute O Oversize >7.5 X >7.5 Minute 2 Double 7.5 X 15.0 Minute I Island vary PROJECTION Projection of map sheet NOTES Notations 21 DRGs are images of 1:25,000 scale 7.5' x 15' USGS topo maps. These USGS products were created in place of the 1:24,000 7.5 minute format in limited areas of the United States, and each map sheet covers an area equivalent to two adjacent 1:24,000 quads. These maps occur in portions of Trinity, Shasta and Tehama counties, and one area on the California-Nevada border. These DRGs are named according to their 1:24,000 map name. For example, ONO EAST (o40122d5) and ONO WEST (o40122d6) are identical images of the ONO 7.5 X 15 Minute map. OCODE 1:24,000 MAP NAME 1:25,000 MAP NAME o39119h8 SEVEN LAKES MOUNTAIN DOGSKIN MTN o40122a7 SOUTH YOLLA BOLLY MOUNTAINS SOUTH YOLLA BOLLY o40122a8 SOLOMON PEAK SOUTH YOLLA BOLLY o40122b7 TOMHEAD MOUNTAIN NORTH YOLLA BOLLY o40122b8 NORTH YOLLA BOLLY NORTH YOLLA BOLLY o40122c5 CHICKABALLY MTN EAST CHICKABALLY MTN o40122c6 CHICKABALLY MTN WEST CHICKABALLY MTN o40122c7 BEEGUM BEEGUM o40122c8 PLATINA BEEGUM o40122d5 ONO EAST ONO o40122d6 ONO WEST ONO o40122d7 ARBUCKLE MOUNTAIN CHANCHELULLA PEAK o40122d8 CHANCHELULLA PEAK CHANCHELULLA PEAK o40123a1 WRIGHTS RIDGE FOUR CORNERS ROCK o40123a2 FOUR CORNERS ROCK FOUR CORNERS ROCK o40123b1 BLACK ROCK MOUNTAIN BLACK ROCK MTN o40123b2 SWIM RIDGE BLACK ROCK MTN o40123c1 PONY BUCK PEAK PONY BUCK PEAK o40123c2 SMOKY CREEK PONY BUCK PEAK o40123d1 WILDWOOD DUBAKELLA MTN o40123d2 DUBAKELLA MOUNTAIN DUBAKELLA MTN DATAFILE NAME: DRGINDEX.PAT RECORD LENGTH: 70 COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ------------------------------------------------------------- 1 AREA 8 18 F 5 9 PERIMETER 8 18 F 5 17 DRGINDEX# 4 5 B - 21 DRGINDEX-ID 4 5 B - 25 OCODE 8 8 C - 33 MAPNAME 31 31 C - 64 USGS100 3 3 C - 67 USGS250 2 2 C - 69 CD 2 2 C - AREA: The area of the polygon in square coverage units. PERIMETER: The length of the polygon perimeter of the polygon in coverage units. DRGINDEX#: The software-assigned unique integer identification number. DRGINDEX-ID: A user-assigned identifier number. OCODE: USGS coding convention for 7.5 X 7.5 minute quads. MAPNAME: Name of 7.5 X 7.5 minute quad map. USGS100: Three character USGS code for 1 degree by 30 minute (100K) quad containing the polygon. USGS250: Two character USGS code for 2 degree by 1 degree (250K) quad containing the polygon. CD: CD number - index to which CD the image is on.