Cadastral surveying involves the delineation of property boundaries and the extent and documentation of easements and restrictions (imposed by private or public law), forming the foundation for Land Administration (LA). Survey models and processes constitute vital parts of Cadastres and Land Administration Systems (LASs). However, these models are often inadequately documented and lack standardization in practice. To address the global diversity and complexity of legal and administrative challenges in LA, standardization efforts have yielded the ISO 19152:2012 (ISO, 2012) Land Administration Domain Model (LADM), the Global Land Tool Network's (GLTN) Social Tenure Domain Model (STDM), and the OGC LandInfra/InfraGML standard. The current edition of the LADM focuses on standardised conceptual modelling of LA-related information, including a dedicated sub-package for Spatial and Surveying representation. As part of the ongoing LADM revision, a refined survey model is being developed to support a broad range of surveying and data acquisition approaches and levels of accuracy. Recognizing that surveying technology is not bound by national practices and regulations, this paper focuses specifically on the surveying aspect of LADM. It illustrates that the proposed refined survey model is applicable not only to conventional real property formation but also to participatory land rights recordation processes. The approach adopted in this research is technology-neutral, accommodating the ongoing evolution of surveying technology. It offers support for a broad range of surveying and data acquisition approaches, with varying levels of accuracy. As the demand for high-precision positioning has been persistent within the land mapping and surveying community, particularly since the initial adoption of GPS, aiming to achieve centimetre-level accuracies (initially confined to local services), the paper addresses the fundamental principles of the High Accuracy Service (HAS) concept within the proposed model. The main results presented in this paper are the conceptual model of the refined survey model of LADM Edition II (ISO19152–2), as well as an abstract, reference, cadastral surveying workflow following the principles of the proposed model.

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The ISO 19152:2012 Land Administration Domain Model (LADM), focuses on standardised modelling of land information at the conceptual level, and together with LADM’s three main packages, it has a dedicated sub package for Spatial and Surveying representation. The first edition of the standard provides multiple spatial representations, and a rather generic survey model based on the ISO 19156:2011 Observations and Measurement Standard (O&M). As an ISO standard, the LADM is subject to periodic revision, and currently, its revision is ongoing and among other refinements, the enhanced support of the surveying model, both at conceptual and implementation level is expected. In this scene, in order for LADM to support a broad range in surveying and data acquisition approaches and accuracies, a refinement is ongoing considering the recent evolution of technology and the encodings used in practice. Therefore, a refined survey model has been prepared and is included at the New Working Item Proposal for LADM Edition II – Part 2, with various data acquisition techniques, as presented in this paper. Based on it and on the experience and requirements from the industry and the standardization organisations, this paper presents the requirements that encoding formats should fulfill to support the revised surveying model. @en

The origin of surveying has a close connection with the designation of land boundaries, while cadastral surveying is a means of defining the limits of properties, thus forming the basis for land administration, serving as an important tool to gather, assess, and update geographical spatial data. Accurate description and record of land are the fundamentals to their rational use and conservation and form the core of wellestablished Land Admini stration Systems (LASs). Although surveying models and approaches are important for Cadastres and LASs, they are not always documented in detail, while with the rapid advances in technology and geoinformation they need to be revised quite often. The ISO 1 9152:2012 Land Administration Domain Model (LADM), which focuses on standardised modelling of information at the conceptual level, has a dedicated sub package for Spatial and Surveying representation. The first edition of the standard provides multiple spa tial representations, and the ongoing LADM revision shall support a broad range in surveying and data acquisition approaches and accuracies, considering the evolution of technology and the encodings used in practice. A conceptual model of the refined surve y model is expected to be included in Part 2 of the new edition of the standard, while its technical implementation(s) covering both 2D and 3D boundaries in Part 6. This paper aims to present the fundamentals of the refined Survey Model of LADM Edition I considering the need to support the interconnection with the everI, evolving surveying methods and acquisition techniques in a standardised way, including among others the Galileo High Accuracy Services requirements and the alignment with other standards, as well as participatory methods. One of the standards which synergy with LADM is investigated in this paper is the OGC LandInfra, and specifically Part 6 “Survey”, that provides a framework for information about observations, processes and their results collected during survey. The development of the proposed model was informed by two case studies using survey plans according to Danish practice and cadastral data from the Hellenic Cadastre.@en