1975 NOS-T Shorelines Digitized by DNR Abstract: Digital shoreline vectors derived from bromide or mylar copies of National Ocean Service T-sheets or hydrographic surveys. Area covered includes Chesapeake Bay and tidal tributary shorelines along the western side of the Chesapeake Bay and five 7.5 quadrangles on the lower eastern shore of the Chesapeake Bay. Purpose: Digital shoreline vectors are used to overlay orthophoto base map rasters of the Maryland shoreline. Acquired as part of multi-year Shoreline Changes mappingproject to show erosion and other shoreline shifts along Marylands Chesapeake Bay and tidal tributaries. Supplemental_Information: The complete data set consists of data collected from 121 NOS T-sheets. The shorelines have been manipulated so that the available data are in 7.5-minute quadrangle format, which may or may not have coincidental T-sheet boundaries. Combined, the 121 digital T-sheets represent 56 7.5-minute quadrangles in nine Maryland counties. A list of the quadrangles and counties available is included in Appendix 3. Shorelines by T-sheet are not available. Two other appendices have been included. Appendix 1 contains information about each T-sheet, such as the T-sheetnumber, scale, and designated shoreline year. Appendix 2 is the Maryland Department of Natural Resources (DNR) Licensing Agreement for Spatial Data and Spatial Data Transfer.A copy of this agreement must be signed by all purchasers and users of DNRs digital data. The form also includes a price list for all quadrangle files and merged county files. Thefiles have been merged with the Maryland Geological Surveys historical shoreline series. These data are available in the same format as the NOS Shoreline series and have their own metadata, which will be made available to all recipients of files that include the historical shorelines. Scale of NOS-T paper base maps varied from 1:5,000 to 1:10,000
1975 Horizontal AccuracyHorizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Accuracy of these digital vectorsis based on the use of source material which was compiled to meet NationalMap Accuracy Standards (NMAS). NMAS horizontal accuracy requires that atleast 90% of points tested be within 0.02 inches of true position. At 1:5000,1:10000 and 1:20000, this value, in feet is 8, 16 and 32, respectively. Ticmarks representing Maryland State Plane Coordinates, geographiccoordinates (latitude/longitude) and/or National Ocean Survey third order orhigher accuracy control stations were digitized and used to register all digitalvectors. At least four points per vector were used for registration, theaverage being 10 different points. Manual registration of the vectors wasdone using MIPS software. After registration, each point was recheckedmanually to determine if the digital product itself complied with NMAS. Anyproduct that didnt comply was separated and reregistered in pieces untilNMA Standards were met. If, after that procedure, segments still did notcomply, they were deleted from the final file.
1994 DOQQ Shoreline Digitized by EarthData Abstract: In 2000, the Maryland Geological Survey (MGS) was awarded a Coastal Zone Management grant to complete the acquisition of a recent (ca. 1990) digital shoreline for thecoastalregions of Maryland - the Chesapeake Bay, its tributaries, the coastal bays, and the Atlantic Coast.MGS contracted the services of EarthData International, Inc. (EDI) of Gaithersburg, Md., to extract shorelines from an existing wetlands delineation, which was based on photointerpretation on 3.75- minute digital orthophoto quarter quads (DOQQs). In areas where a wetland coverage was not yet available, EDI interpreted shorelines directly from the orthophotography. DOQQ registration (Maryland State Plane Coordinate System,NAD 83, meters) was transferred automatically to the shoreline vectors. Following shoreline extraction or interpretation, EDI assigned attributes to the vectors based on shoreline type: beach, vegetated, structure, or waters edge.
Process_Description: Under contract to the Maryland GeologicalSurvey, Earth Data International extracted or interpreted the modern(1988-1995) shoreline directly or indirectly from digitalorthophotography. For all but 35 of the quarter quads, EDI extractedthe shoreline from existing wetlands vectors, previously delineated forthe Maryland Department of Natural Resources (DNR) over 1:1,000-scale DOQQs. The DOQQs, in turn, were derived from 1:40,000-scalecolor infrared (CIR) film. For the remaining 35 quarter quads, theshoreline was interpreted directly from the DOQQs. Horizontal Datum: NAD83 Pixel Resolution: 1 meter Scale: 1:12,000 Individual DOQQs