Shoreline Change Map Data for Tidewater Maryland

For the coastal regions of Maryland, the Maryland Geological Survey (MGS) has
periodically compiled maps depicting shoreline position at several points in
time. The most recent compilation -- the first electronic one -- involved (1)
digitizing historical (1841-1977) shoreline maps, all derived directly or
indirectly from National Oceanic and Atmospheric Administration coastal survey
maps (topographic or T-sheets), and (2) interpreting recent (1988-1995)
shorelines from digital orthophotography. MGS is using the shorelines to update
a series of Shoreline Changes maps and to determine coastal land loss, by
watershed and by county, during the last half of the 20th century.

This data set contains past shorelines, dating from 1841 to 1995, for 125
7.5-minute quadrangles covering the coastal regions of Maryland (see below).
Originally in MicroImage's TNTmips .rvc format, the shoreline vectors have been
converted to Arc/Info "Export" (.e00) format. They are registered to the
Maryland State Plane Coordinate System (North American Datum of 83, meters).

Spatial Reference Information:

-Map Projection Name: Lambert Conformal Conic
-Grid Coordinate System Name: State Plane Coordinate System 1983
-SPCS Zone Identifier: 1900 (Maryland)
-Planar Distance Units: meters
-Horizontal Datum Name: North American Datum of 1983
-Ellipsoid Name: Geodetic Reference System 80
-Semi-major Axis: 6,378,137 meters
-Denominator of Flattening Ratio: 298.257
-Depth Datum Name: The aerial photography from which the DOQQs were
developed was not tide-coordinated. Therefore, shorelines in this data
set does not represent a consistent vertical datum.

Shoreline Attributes:

-beach
-vegetated
-structure
-water edge

All four categories are linear features, except "beach" which, if
sufficiently wide, can be both linear and polygonal. Shorelines were merged
into 7.5-minute quadrangles, provided that the aerial photography on which the
DOQQs were based was flown in the same year

[Summary provided by the Maryland Geology Survey.]