When a coastal structure is photographed at low tide, an accurate permanent 
record of all visible armor units is obtained. Through the use of stereoscopic 
photogrammetric instruments in conjunction with photographs, details of struc- 
ture geometry can be defined at a point in time. By direct comparison of photo- 
graphs taken at different times, as well as the photogrammetric data resolved 
from each set of photographs, geometric changes (i.e., armor unit movement 
and/or breakage) of the structure can be defined as a function of time. Thus, 
periodic inspections of the structures will capture permanent data that can be 
compared and analyzed to determine if structure changes are occurring that indi- 
cate possible failure modes and the need to monitor the structure(s) more closely. 
The Ofu Harbor breakwater, American Samoa, was nominated for periodic 
monitoring by the U.S. Army Engineer Division, Pacific Ocean (CEPOD). 
Three additional CEPOD projects have been monitored previously under the 
Periodic Inspections work unit. Base conditions have been defined for break- 
waters at Kahului Harbor, Maui, HI; Laupahoehoe Boat Launching Facility, 
Hawaii, HI, (Markle and Boc 1994); and Nawiliwili Harbor, Kauai, HI (Bottin 
and Boc 1996). 
Project Location and History 
American Samoa is a group of seven islands (five volcanic islands and two 
coral atolls) located in the South Pacific Ocean. These islands lie at approxi- 
mately 170 deg west longitude and 14 deg south latitude and comprise a total 
area of about 200 sq km (76 sq miles).' They are located about 6,700 km 
(4,150 miles) southwest of San Francisco, California, and about 3,700 km 
(2,300 miles) south-southwest of Hawaii (Figure 1). 
The five major inhabited islands of America Samoa are Tutuila, Aunuu, Ofu, 
Olosega, and Tau. Tutuila, the largest and principal island, is the center of gov- 
ernment and business. Aunuu lies 1.6 km (1 mile) off the east coast of Tutuila. 
The three islands (Ofu, Olosega, and Tau) are collectively referred to as the 
Manu'a Islands and are located 106 km (66 miles) east of Tutuila. Ofu and 
Olosega are often called sister islands because they are separated by less than 
275 m (900 ft) of shallow reef. 
The American Samoan Islands were discovered in the 1700's by Dutch navi- 
gators. However, the islands remained unclaimed until the 1900's, when the 
chiefs of the islands ceded title to the United States (CEPOD 1973). The 
U.S. Navy administered the islands as a U.S. territory until 1951, when the 
U.S. Department of the Interior assumed administration. Its inhabitants are 
American nationals, but not citizens. They may visit or emigrate to the United 
States without passport. 
1 Units of measurement in the text of this report are shown in SI units, followed by non-SI units in 
parentheses. In addition, a table of factors for converting non-SI units of measurement used in 
figures in this report to SI units is presented on page vi. 
Chapter 1 
Introduction 
