The join of remote sensing and GIS(Geographic Information System) could be useful in various fields of marine information and land information as well as ITS(Intelligent Transport Systems). This paper is LPF(Low Pass Filtering) for the extraction of island detection in coastal zone Iron SPOT imagery which is 10m resolution photograph. The study area is based on the southern sea in korea. Sobel operator performed the extraction of island detection in coastal zone after the LPF processing by remote sensing. And, GIS was used to generate from raster to vector data. As the result, The best way prove out the 5${ imes}$5 convolution mask about the LPF processing of island detection in coastal zone. It is judged the research which it sees with the fact that the presentation of very scientific and reasonable data will be possible from the oceanic dispute will occur from the EEZ(Exclusive Economic Zone).