A smoothing method of lofargram using morphological Opening filter

Abstract

Averaging procedure, which is one of the data smoothing methods, is generally used to obtain a fine-quality lofargram. However, the procedure causes to spread impulse noise over time-axis on the lofargram. In this case, it is difficult to distinguish target signal from received signal on the lofargram. In this paper, we propose Variable Time-Resolution Lofargram using Morphological Opening Filter to suppress the impulse noise on lofargram instead of averaging procedure. The computer simulation results in this paper shows effective improvements of processing gain and time-resolution as compared with that of averaging procedure.