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November 1, 1996 Texas Department of Transportation (TxDOT) (** This data set now only contains the GIS corrected TxDOT urban/county files.) Digital County/Urban Map Files I. Map Content TxDOT county/urban map files were digitized from USGS 7.5 minute quadrangles. Updates are made using TxDOT Highway Construction Plans, Aerial Photographs, Official City Maps and Field Inventory. These files contain most of the features found on 7.5 minute quads, except for items such as contour lines, fence lines, jeep trails, electrical transmission lines, oil and gas pipelines and control data monuments. II. Map Projection These files are based on the following map projection system: TEXAS STATEWIDE MAPPING SYSTEM (NAD 27) Available formats: DGN, DWG, & DXF Projection: Lambert Conformal Conic Spheroid: Clarke 1866 Datum: North American 1927 Longitude of Origin: 100 degrees west (-100) Latitude of Origin: 31 degrees 10 minutes north Standard Parallel # 1: 27 degrees 25 minutes north lat. Standard Parallel # 2: 34 degrees 55 minutes north lat. False Easting: 3,000,000 feet (914,400 meters) False Northing: 3,000,000 feet (914,400 meters) Unit of Measure: feet (international) TEXAS STATEWIDE MAPPING SYSTEM (NAD 83) Available formats: Arc/Info Export (e00) Projection: Lambert Conformal Conic Spheroid: Clarke GRS80 Datum: North American 1983 Longitude of Origin: 100 degrees west (-100) Latitude of Origin: 31 degrees 10 minutes north Standard Parallel # 1: 27 degrees 25 minutes north lat. Standard Parallel # 2: 34 degrees 55 minutes north lat. False Easting: 1,000,000 meters False Northing: 1,000,000 meters Unit of Measure: meters III. Positional Accuracy These digital maps were created primarily for the purpose of producing county/urban published maps, certain features - particularly railroads, have been displaced in congested areas so as to insure map readability at county map scales.Although TxDOT makes no official claim as to the positional accuracy of these maps, given the USGS stated positional accuracy of plus or minus 40 feet for its 7.5 minute quads, and the inadvertent positional shifts that may have been introduced during the digitizing process, TxDOT estimates that the positional accuracy of most features will be approximately plus or minus 50 feet. IV. Tables and Libraries These files have been furnished with the following tables and libraries: txdot.ctb (color table) txdot.flb (high resolution bit stream font library) txdot.cel (cell library) V. County Map Levels TxDOT uses the following level structure for its county/urban maps. These following features are found in (county number) cnty.dgn and (county number)urban.dgn files. Feature Level Highway Number and County Line .............................. 1 Highway Boulevard and State Line ............................ 2 Frontage Road / Ramp ........................................ 3 Highway Boulevard Centerlines ............................... 4 Highway in City ............................................. 5 Pedestrian Overpass ......................................... 6 Blank ....................................................... 7 Highway Rural ............................................... 8 Bridges on Boulevard Highways ............................... 9 Highway Shields ............................................. 10 Bridge on Highways in Cities ................................ 11 Bridge on Rural Highways .................................... 12 Blank ....................................................... 13 Culture Names ............................................... 14 City Street Boulevard Roadways .............................. 15 City Street Boulevard Centerlines ........................... 16 Concrete Ford ............................................... 17 City Streets ................................................ 18 Street Names (on Urban files only) .......................... 19 County Road Bridges ......................................... 20 Rural Subdivision Streets ................................... 21 Earth County Roads .......................................... 22 All Weather County Roads .................................... 23 Paved County Roads .......................................... 24 Rural Subdivision Boulevard Centerlines....................... 25 Rural Subdivision Boulevard ................................. 26 Railroad: Main Line Pattern and Name ........................ 27 Railroad Main Line .......................................... 28 Railroad: Spur Line Pattern ................................. 29 Railroad Spur Line .......................................... 30 Railroad Bridge ............................................. 31 Blank ....................................................... 32 Blank ....................................................... 33 Water Feature Names ......................................... 34 Flume ....................................................... 35 GIWW Channel Centerlines .................................... 36 Intermittent Streams ........................................ 37 Flowing Streams and Small Rivers ............................ 38 Lakes ....................................................... 39 Medium Flowing Rivers ....................................... 40 Large Flowing Rivers ........................................ 41 Intermittent Lakes .......................................... 42 Inundation Line ............................................. 43 GIWW Canal (through water) and Channel Names ................ 44 GIWW Canal (through land) and Barge Symbol .................. 45 Dam ......................................................... 46 Mask for Barge Symbol ....................................... 47 Escarpment, Bluff ........................................... 48 Mountain Range and Prominent Peak Symbol .................... 49 Blank ....................................................... 50 State Line Monument ......................................... 51 Boundary Lines .............................................. 52 Airport Runways ............................................. 53 Public Facility Symbols ..................................... 54 Culture Symbols ............................................. 55 Government Symbols .......................................... 56 Town Symbols, City Names and Population ..................... 57 City Limit Lines ............................................ 58 Bubble Inset Lines .......................................... 59 Asterisks and Mileage Between Points ........................ 60 Asterisks Masks ............................................. 61 ------------------------------------------------------------------ VI. Contacts for Additional Information Each county directory has a (county number)hist.dat file listing the responsible operator and their phone number. If further clarification is needed please contact: Will Watson (512) 486-5094 For information concerning CD, please contact: Texas Natural Resources Information System P.O. Box 13231 Austin, Texas 78711-3232 Scott D. Grant phone: (512) 463-8862 fax: (512) 463-7274 e-mail: info@tnris.state.tx.us |
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