Currency of GIS databases, especially base map data, is strongly required in many GIS applications. It is expected that local government can keep base map data current very efficiently by using administrative information (building permit, notification of house demolition etc.) which is collected through daily routine. A unige contribution of this study is a comparative evalution of the efferctiveness of the administrative information in keeping base map data current on the quantitative basis using actual data. The authors use an expected variance of the number of buildings as a measure for evaluating the completeness of base map data.
Actual percentage of building emergence and demolition covered by the daily administrative information (building permit, notification of demolition and ground survey for fixed property taxation) are surveyed from 1988 to 1991 in a study area of a local city with 500, 000 population. The survey shows 4-6% of the emergence and demolition were not captured. It is concluded that daily administrative information can not be a single data source in keeping the currency (completeness) of building data over long years. The appropriate combination of aerial survey and administrative data usage is suggested.
Through a comparision of update methods combining administrative data and aerial survey data with a conventional aerial survey method in terms of the completeness of building data and total cost of update, it is demonstrated that the combining method is more advantageous in case higher priority is attached to currency of building data.
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