Additional Tables and Examples.
Tables 1 and 2 are experimental values for single pass PODs. The tables included here (Tables 3, 4, 5, and 6) are for use when a helicopter passes over a search area multiple times.

Tables 3 and 4 may be used to determine the range of values for the cumulative POD obtained by searching an area multiple times with a helicopter. In these tables, the column on the left is the number of times the area is searched; the row across the top is the confidence level required. Each square in the body of the table contains two numbers: the cumulative POD corresponding to the smallest and largest interval values for the single pass POD given in Table 1 or Table 2. [The cumulative POD is given by the equation

where p is the single pass POD and m is the number of passes made over the area].

Example 1. On an overcast day, a helicopter of the type described in this report searches an area 3 times. What is the range of values for the cumulative probability of detection (POD) at a confidence level of .757

Answer. Using Table 4 (overcast day), the confidence level of .75 is found in the top row. The number of passes (3) is found in the column on the left, and from the body of the table it is seen that the cumulative POD is at least .884 but not more than .995. In other words, one is sure at the 75% confidence level that the area has been covered with a cumulative probability of detection of at least 88.4% but not more than 99.5%.

Tables 5 and 6 may be used to determine how many passes must be made over an area in order to obtain a cumulative POD of at least a desired level. In addition, these tables contain factors in parentheses which, when multiplied by the total size of the search area (in square miles) will yield the approximate number of helicopter hours needed to accomplish a desired cumulative POD. This number is based on a "creeping line" pattern which covers one square mile in 9 minutes.

In Tables 5 and 6, the column on the left is the cumulative POD desired and the row across the top is the confidence level required. The body of the tables consists of squares which contain two numbers, one of which is in parentheses. The number which is not in parentheses is the number of helicopter passes over the search area needed to achieve a cumulative POD of at least the value given in the column at the left. The number in parentheses is the factor by which the total area (in square miles) is multiplied in order to yield the number of helicopter hours needed to produce such a cumulative POD.

Example 2. It is bright and sunny, and the search area is 15 square miles. How many passes of the helicopter and how many helicopter hours will be required to achieve a cumulative probability of detection (POD) of at least .7 with a confidence level of .85?

Answer. From Table 5 (bright, sunny) the confidence level (.85) is found along the top row and the cumulative POD of at least .7 is found in the left most column. From the table it is seen that 7 passes of the helicopter are needed. To determine the approximate number of helicopter hours required, the number in parentheses (0.8) is multiplied by the size of the search area (15 square miles): (0.8) x (15) = 12 hours.