Abstract: An approach for contour generation and filling of irregular regions based on rectangular grid method is proposed. This approach entails contour generation in a rectangular area containing the irregular region of interest using rectangular grid method, followed by removal of the equivalent points outside the irregular region. An improved algorithm of ray method to determine the spatial relation between the equivalent points and irregular region is also reported. The above method has been successfully used in a geological disaster monitoring platform for drawing the isopleth maps of rainfall and soil moisture content in various regions.