36 



presented in Appendix B. Both the plots and tabular data show close 

 comparison between ground and aerial survey data. No storm conditions 

 occurred between the September 1991 ground survey and the October 1991 

 aerial flights, so no armor unit movement was anticipated. Therefore, these 

 two data sets provide a good check of the accuracy of the photogrammetric 

 analyses. The data show typical differences of a few hundredths of a foot 

 between the ground and aerial surveys of targets. Maximum differences were 

 equal to or less than 0.17 ft, and this level of difference was rare in the data 

 set. In the armor unit movement analysis discussed later in this report, efforts 

 were made to resolve magnitudes of armor unit movement that equaled or 

 exceeded 0.5 ft. These data show that this accuracy can be resolved using 

 photogrammetric analysis. 



Photo Maps 



Aerial images were used to produce halftone, screened, and rectified photo 

 maps of the armor unit fields and concrete rib cap areas on the East and West 

 Kahului breakwaters and the entire Laupahoehoe breakwater. These photo 

 maps are in positive reverse reading form on 28-in. by 40-in. double-matte 

 Mylar sheets and were produced at a scale of 1 in. equals 20 ft. These high- 

 resolution maps allow for visual inspection of the above-water portions of the 

 breakwaters and comparison between maps produced during different time 

 periods. Reduced reproductions of the 10 October 1991 photo map for 

 Laupahoehoe, and 8 January 1993 photo maps of Kahului West and Kahului 

 East, are presented in Figures 20-22, respectively. Full-scale, original photo 

 maps for both years' aerial flights are on file at the authors' offices at WES 

 and POD. 



Armor Unit Movement Detection 



A methodology was developed to detect movement that occurred between 

 successive aerial surveys of all armor units visible above the waterline. 

 Breakwater stereo pairs taken during the first year's flight were mounted in 

 the stereoplotter and the XYZ coordinates of three prominent, reproducible 

 points on each visible armor unit were read and recorded in a computer file. 

 The second year's stereo pairs then were analyzed in the same manner. The 

 two coordinate files then were converted to AutoCAD files and when both 

 files were displayed on a video screen armor unit, movement between the two 

 years was easily detected. Coordinates of the points for the armor units which 

 appeared to show movement equal to or greater than 0.5 ft were stored to a 

 separate file and magnitudes of the XY vector changes for each of the three 

 points on the armor unit were calculated. Table 7 presents the data on 

 10 armor units that met or exceeded the threshold movement between the 1991 

 and 1993 aerial flights. All of these units were on the Kahului breakwaters 

 (six and four on the west and east breakwaters, respectively). No units 



Chapter 2 Monitoring Plan and Data 



