On the positional enhancement of digital cadastral maps

In recent years, there is a renewed interest in the development and enhancement of legal digital cadastral databases. These databases usually are derived from paper parcel maps by manual or automatic conversion processes. Nevertheless, the converted cadastral data should be further processed to minimize inherent errors in the data conversion procedure, to resolve inaccuracies in the original parcel maps, and to fit them to the new GPS-based coordinate system with high precision. This paper describes a workflow of steps used to enhance and improve the spatial accuracy of digital cadastral maps. Every step in this workflow is analyzed and various problems are uniquely addressed. First, the problem of determining the correct coordinate transformation model is investigated using the Akaike's Information Criterion (AIC). Second, the problem of modifying boundary corners to fit existing ground features is solved by using a unique rubber sheeting procedure that takes into account linear features. Last, an adjustment with stochastic constraints is applied to include additional cadastral information and geometric conditions. The developed methodology is tested and applied in a practical case study.