An-Najah Staff

Several approaches exist for the creation of a digital cadastral overlay.  These range from the simple digitization of existing paper property ownership maps, to the extensive field resurvey of all cadastral parcels.  While the digitizing approach is relatively inexpensive, and can be implemented in a short time period, it does not provide sufficient accuracy to satisfy all land information users due to the accuracy limitations of these paper maps.  On the other hand, even though the resurvey approach achieves high accuracy, it requires high up-front finances and takes a long time to implement. There is consequently a need for another approach for building the cadastral overlay which gives greater weight to the efficiency and cost factors, at least in the initial phase of implementation. This approach should start with coordinates digitized from existing paper ownership maps and upgrade their accuracy incrementally through least-squares adjustment techniques using geometric constraints as well as accurate survey data as they become available. These constraints include parcel areas, street widths, continuity of lines and curves, known azimuths and angles, particularly those which are multiples of 90°, in addition to others, and will be treated as "stochastic constraints" to take into account the deviation of the real situation from the ideal.  This paper outlines the details of such an incremental approach and reports on some of the encouraging results which have been achieved. If integrated with existing Geographic Information Systems (GIS), this approach should significantly enhance the capabilities of these systems, particularly in the area of land records modernization.