The effects of control point shape and distribution in the creation of a numeric cadastral data base

For centuries information describing a parcel of land has been presented in the form of a hard copy parchment or document. The information displayed on the face of such a document has traditionally shown a direction and a distance along each line of each parcel. Since the advancement of angle and distance reading instruments the accuracy of such plans has improved substantially. In saying this surveyors dealing with older plans must determine, based on a hierarchy of evidence, how to deal with the inconsistences between what is shown on the cadastral survey plan and what is actually marked on the ground. Recent advancements in processing power and surveying instrument capabilities have led to the creation of what is known as a Numeric Cadastral Data Base (NCDB). Most states in Australia currently utilize what is known as a Digital Cadastral Data Base (DCDB), which has limitations due to the way it was originally created. A NCDB however is created by entering the cadastral/boundary information from the original survey plan into a software package and then adjusting the network in conjunction with the physical survey marks on the ground. The result is a survey accurate data base which has the potential to be used as a means of better defining parcel boundaries. This dissertation will investigate the processes involved in the creation of a NCDB and the effects of control point selection within the cadastral adjustment. The results will show that the closest representation to the boundaries actual position is achieved from the adjustment by using all of the original survey marks. It was found that as control is added to the adjustment the mean difference between the actual boundary corners and the adjusted corners became less over a test area of 49 parcels consisting of 147 corners. The research is supported by the Northern Territory Department of Lands, Planning and the Environment (DLPE) and will contribute to the developing NCDB of the town of Alice Springs