McCaffrey, C.A. and R.D. Dueser. 1990. Plant associations on the Virginia
Barrier Islands. Virginia Journal of Science 41(4A):282-299.

Digital versions of the maps included in that article were digitized by
John Porter and Raymond Dueser.

Information on the data:

The ARC/INFO export files in this directory were produced by ARC INFO version

Geographical UTM coordinates are based on NAD-27 from USGS Quad
sheets. Due to lack of ground reference points on most maps,
geographical accuracy is on the order of +- 100 m.

Maps were hand-drawn in 1975 using 1:20,000 scale aerial photography
in 1974 by Cheryl McCaffrey.

Codes for vegetation classes are:

      0        w        Water/background
      1        A        Foredune Grassland
      2        G        Dense Grassland
      3        AG       Beachgrass Dunes/ Dense Grassland Dunes
      4        g        Sparse Grassland
      5        Ag       Foredune - Sparse Grassland Complex
      6        At       Open Dunes - Thicket Complex
      7        B        Beach
      8        T        Tall Thicket
      9        AT       Open Dunes - Thicket Complex
     10        t        Low Thicket
     11        J        Juniper Thicket
     12        P        Pine Forest
     13        H        Hardwood Forest
     14        PH       Pine-Hardwood Forest Complex
     15        m        Low Salt Marsh
     16        Mm       Upper Low Salt Marsh
     17        M        Brackish Marsh
     18        s        Salt Flat
     19        F        Fresh Marsh
     20        w        Open Water
     21        dr       Drift
     22        b        Submerged Sand
     23        uw       Underwater Flora (or Fauna)
     24        peat     "Peat" Outcrops
     25        wf       Wash Flat
     26        mf       Mud Flat
See the above citation for details on the mapping units.

Maps were originally digitized into a 2-m raster format with ERDAS and
then later converted to a vector format in ARC INFO and corrected for
digitizing and thematic errors. For this reason, most lines have
stairstepping. An exception is Myrtle and Mink Islands which were
digitized directly into ARC/INFO vector format.