DATA CITATION 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 6.1. 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: GRID-CODE VEG_CODE VEG_CLASS 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.