12 
Soft wet flat terrain with few high points for survey stations. 
Poor visibility during early morning fog and afternoon air refraction. 
High vegetation. 
Time-consuming and circuitous access by boat. 
Soft tidal flats that deny access at low tide. 
Difficult walking conditions. 
The field survey costs for 1:10,000-scale maps are probably at least an 
order of magnitude greater than for the standard 1:24,000-scale maps and are 
the major cost for a wetland map. 
It was our intent to show major species composition on the wetlands maps, e e 
Since this is a basis not only for determining marsh boundaries but also for | 
evaluating marshes for management and regulation. We were not, however, 
interested in detailed biological mapping. Where plant associations exist, 
the general composition is indicated, but no attempt was made to delineate 
each species in & mixed area. Where an entire area is covered by one species 
with only a 10- to 12-foot border of other marsh species along the upland 
boundary, only the major species are indicated. Areas disturbed by man's 
activity--ditches or spoil disposal--were field checked, and a uniform inter- 
pretation applied. 
It is not our intent to establish a precise relationship between a partic- 
ular stage of tide and the marsh vegetation and morphology. The cartographic 
representation of wetland features is still subject to ground verification in 
any legal action. Nevertheless, the orthophotoquad is a valuable tool to 
implement Federal and State responsibilities for planning, mapping, inventory, 
regulation, and management. 
| 
CONCLUSION @ | @ 
The objective of the Sapelo Island research project was to evaluate require- 
ments, procedures, and costs for coastal wetland mapping using remote sensing 
techniques. The 1:24,000-scale topographic maps form the primary cartographic 
base for the landward portion of the coastal zone, but they have limitations 
of accuracy and content. Geodetic and tidal datums cannot be directly equated, 
and the accuracy of contour and tide elevations is limited by practical con- 
siderations of marsh morphology. 
Orthophotoquads at various scales are seen as an essential prerequisite for 
wetland mapping. Of course, Federal and State statutes will strongly influence 
mapping criteria. Vegetation interpretation from color infrared photographs is 
a practical, economical, and accurate technique for establishing wetland boundaries, 
helped by the fact that there is a uniquely small number of major coastal species. 
Using this method, the upper wetland boundary can be delineated to meet NMAS. 
  
Credits 
Appreciation is due the entire staff at the University of Georgia Marine Institute o 
at Sapelo Island for their assistance, advice, and hospitality.