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The black-and-white photographs for the orthophotoquads were obtained on 
March 22, 1973, near mean high tide. The flight height was 40,000 feet, and 
each exposure was quad-centered on the 2.5-minute by 3.75-minute format. A 
K&E camera with a 305-millimetre focal-length high-resolution lens was used 
with a Wratten #25 filter and Kodak 2402 film. The exposed film was processed 
to a 1.3 gamma--somewhat higher than usual because of the 40,000-foot flight 
height, which causes a lower contrast due to increased atmospheric haze. On 
such a base, detail interpreted from additional color infrared photos--the 
upper wetland boundary and the major marsh species associations--are delineated. 
During the same flying mission, additional coverage was obtained with 
various combination of films, filters, focal lengths, and flight heights. The 
resultant photographs are being evaluated for coastal-zone mapping, assessing 
not only the image quality of marsh and water features but also upland detail 
of roads, houses, and vegetation. Although most coastal areas are relatively 
flat, about 35 percent, including some adjacent uplands, have sufficient relief 
(50 feet or more) to require differential rectification on an orthophotoprinter. 
The narrow angle of the 305-millimetre focal-length lens reduces the number of 
differential rectification operations because simple rectification and enlarge- 
ment can be substituted. Also, for the 1:10,000-scale format, no mosaicking of 
images is required since each exposure can be quad-centered at flight heights 
above 30,000 feet. With a 155-millimetre focal-length camera, a flight height 
of 15,000 feet would be adequate, but the wider-angle lens would increase the 
number of orthophotos requiring differential rectification. 
Color infrared Kodak 2443 film for wetland species interpretation was 
exposed at 40,000 feet with a 155-millimetre Wild RC-8 camera; the tide was 
at mean low stage. The resulting 1:80,000-scale photographs were enlarged 
4X to transparencies and prints at 1:20,000 scale. These were used for pre- 
liminary classifications and delineation, although the early spring flight 
date was not optimal for photointerpretation of vegetation. It appears that 
about 5 man-days are needed to interpret, delineate, and field check the major 
coastal wetland species and the upper wetland boundary over the area of one 
75-minute quadrangle (about 63 square miles). The accuracy of the boundary 
is about 30 feet on the 1:20,000 enlargement and would be adequate for 1:24,000- 
scale wetland delineation. Larger-scale color infrared photography was 
scheduled to achieve the accuracy required for the 1:10,000-scale orthophoto 
base. Unfortunately, it was not obtained and the research had to be concluded 
with extensive field checking and use of some older large-scale color infrared 
photographs covering a small part of the area. The wetland vegetation boundaries 
were transferred from color infrared overlays and field notes to the black-and- 
white orthophotos. It is estimated that an original photo scale of 1:40,000 or 
larger is required for interpretative color infrared photographs if the final 
map scale is 1:10,000. 
Establishing the required horizontal ground control in coastal wetland 
areas can be a major expense. Ground control points are obtained by extend- 
ing positions from existing horizontal control stations to photoidentified 
features. The area around Sapelo Island is fortunate in having many recoverable 
survey stations, but approximately 15 man-days of fieldwork were required to 
survey photoidentifiable control points for the six 1:10,000-scale maps. Precise 
surveys in the coastal wetlands are hampered bv: