Coastal flood is a phenomenon which happens resulting high tide in coastal area, where its location is lower than sea level. This flood accurs in Semarang City, The Province of Central Java, Indonesia. The floods are a very wide. All coastal areas in Semarang City are almost inundated by tidal flood. Therefore, it needs a precise means to map the flood distribution in Semarang City.
GIS raster is a data format which is pixel or cell where it is saved as a value. Raster is used not only to represent a data but also to do a spatial analysis, and the spatial analysis which were done such as flood, health, and environmetal analysis, etc.
Neighborhood Operation is a spatial analysis in GIS technology based on raster, where its function is to analyze which emphasize relationship between location. The technique of neighborhood operation at GIS technology based on raster is obtained in ILWIS software and one of its operation is to map a tidal inundation in sea level.
When applying neighborhood operation analysis at tidal inundation, the analysis is done to pixel in raster map using set of 3x3 pixel matrix. The analysis is done using sintax which is built following a logic of mathematical equation, which is applied to an input map. The spatial analysis using neighborhood operation can be developed with integrating iterative mathematical operation. Integration of neighborhood operation and iteration is applied to do modelling distribution of tidal inundation. Using an input map (i.e. elevation digital data in Semarang Coastal Area) and elevation data of sea tide can be determined tidal inundation area on 60 cm elevation.