Cadastral Triangulation: A Block Adjustment Approach for Joining Numerous Cadastral Blocks

Authors

• Michael Klebanov
• Yerach Doytsher

Keywords:

Coordinate based cadastre, boundary matching, least squares adjustment, block adjustment by independent models

Abstract

In the last decade or so, there has been a very clear transition in many countries throughout the world from a graphical cadastre and/or relatively non-accurate digital cadastre toward an accurate coordinate based legal cadastre. Aiming at defining accurately the turning points position of the cadastral sub-division based on current data without the need to re-measure the cadastral entities, motivates the development of new algorithms and approaches suitable to performing the task. Implementation on a nationwide level requires to first develop advanced mathematical algorithms and methods to process separate parcellations (cadastral blocks or mutation plans), and then additional algorithms and methods to combine the numerous separate parcellations into a cadastral continuity maintaining rigid topological compatibility. Practical experience, especially from the Israeli viewpoint, indicates that implementation of advanced computational techniques for processing separate cadastral blocks, is only a partial solution of the problem. An optimal joining of the separate cadastral blocks into a homogeneous seamless cadastral space constitutes a complex task due to discrepancies between the adjoining parcellations. These discrepancies, significant in terms of their magnitude and characteristics, are mainly caused by the cadastral parcellation process based on separate cadastral measuring projects on the one hand, and limited accuracy of the measuring techniques in previous decades (mainly in the first half of the 20th century) on the other hand. The paper introduces a new algorithm based on the existing mathematical model, customary in photogrammetric mapping, aimed at connecting the adjoining photographs into blocks based on Block Adjustment by Independent Models. The proposed adjustment method (named the "Cadastral Triangulation") is executed based on the classic Adjustment of Indirect Observations combined with the Chained Similarity Transformation. This adjustment process which is carried out by a global transformation mechanism, enables obtaining both optimal transformation parameters of all the separate parcellations, as well as optimal coordinates of the cadastral boundary turning points. The initial results of the proposed method indicate its effectiveness in connecting the adjoining cadastral blocks, effectiveness expressed by a significant decrease of systematic and random errors compared to their pre-adjusted situation. Additionally, the proposed method enables bringing the adjusted cadastral boundary turning points maximally close to their theoretical true (and unknown) locations and, in any case, much closer than locations computed by currently practiced methods. Therefore, the proposed method may effectively be used as a primary computational algorithm for implementing a nationwide coordinate based legal cadastre.