TABLE OF CONTENTS 'Morte point is rocky and barren, sloping from its summit to low cliffs'
West Coast of England Pilot, 1960
Detectability of extended targets depends on several of their parameters.
Mean radar cross section. This term, ?, in the radar range equation, affects echo strength at all ranges. RCS of practical targets such as ships is difficult to measure and more difficult to calculate with any degree of precision. RCS values of a wide range of extended targets are discussed in this chapter. In clear conditions, the echo has only to compete with receiver noise, and quite low RCS may give adequate detection range. But when clutter is severe, higher RCS is necessary.
Fluctuations in RCS. This chapter addresses mechanisms causing RCS fluctuations as the target aspect changes and it heels (rolls or pitches). The effect of fluctuation on detection is considered in Chapter 12.
Effective reflecting height (centroid height). Chapter 9 showed that the effective height of the target as a radar reflector affects the critical or transition range at which the echo changes from an R -4 to an R -8 law, affecting the multipath factor beyond, and hence long-range detectability. Multipath factor is unaffected by target height at short range, but a heavy sea which physically screens or masks low targets reduces the maximum achievable probability of detection even in favourable signal to noise plus clutter ratios.
Physical size relative to the detection cell. At short...
