Rooftop mapping and information system for rainwater harvesting

Malaysia is a fortunate country as it experiences abundant rainfall throughout the year. Thus, rainwater harvesting is an alternative source of consistent water supply to help maintain a sustainable ecosystem. Researchers have studied the components, factors and advantages of this harvesting system, but have overlooked the importance of rooftop mapping and rainwater harvesting database system. Hence, the objectives of this research were to evaluate the accuracy of photogrammetry method for three-dimensional rooftop mapping and develop rainwater harvesting database using geographic information system approach. The final objective was to analyze the performance of the database for related applications. In this study, rooftop mapping was carried out in Lingkaran Ilmu, Universiti Teknologi Malaysia to collect the data required for the database. Then, a digital photogrammetric workstation and SketchUp software were used to generate three-dimensional rooftop maps. The geometric accuracy obtained was 0.79m which was validated by a terrestrial laser scanner. The rooftop mapping data was used as input for the identification of a catchment area, as well as meteorological data in the development of the database. Then, ArcGIS 9.3 software was used to develop the database which could provide the information on catchment and storage system for rainwater harvesting. The findings of the study showed that the total amount of rainwater harvested was 197498.97m3 per year and by using the developed database, it was estimated that the tank size would be 541m3 and tank location would be at 172474.11 Northing, 627057.95 Easting. Thus, the study has illustrated that as a result of the accuracy of the rooftop mapping, a rainwater harvesting database was developed for predicting total rainwater harvested, tank size and location prior to decision making for the future of water supply development