3D Cadastre in Singapore

Property rights have always been shown in 2D with the surface parcel being the fundamental representation of ownership. Complex 3D situations, interlocking properties, multi-levelled train station, underground rock caverns are all immediate but unresolved challenges for us in Singapore. Volumetric parcels such as strata subdivision, subterranean and airspace parcels are currently recorded and represented in 2D plans. Is the 2D system adequate to delineate complex multi-levelled development that we see in Singapore today? Is the 2D information recorded sufficient for stakeholders? As the custodian of authoritative cadastral boundaries in Singapore, there is a great responsibility on Singapore Land Authority to uphold the integrity of the cadastre. Ultimately, the public is depending on SLA to provide accurate and reliable cadastral survey records. The objective of this paper is to describe the current state of the cadastre system in Singapore and the need for implementing a 3D cadastre system. It will also discuss the real world scenarios related to volumetric ownership, examine the driver for 3D cadastre and outline the plan going forward

Towards “Smart Cadastre” that Supports 3D Parcels

Singapore Land Authority (SLA) is the government agency responsible for the cadastral survey and property title registration in Singapore. We have implemented the SVY21 cadastral survey system which adopted the “Coordinated Cadastre” concept in 2004. In 2005, Electronic Submission of cadastral survey jobs and paperless job processing was introduced. Over the last 18 years, we have embarked on various initiatives to modernise our cadastral survey system. Our challenges in maintaining the cadastral survey system are to be able to stay relevant and progress fast enough to support the needs of the industry and general public. That is why SLA is constantly looking for ways to further improve our system and one of the main thrusts moving forward is 3D cadastre. Currently, we use a few IT systems to manage the cadastral survey job submission work flow, to maintain the Digital Cadastral Database (DCDB) and to maintain parcels attribute (textual) information. Cadastral plans are submitted in raster format together with final coordinates for each land parcel in ASCII format for the purpose of DCDB. Volumetric parcels such as airspace lots, subterranean lots and strata lots have been implemented in Singapore for more than 15 years. However the airspace and subterranean lots survey plans produced are in planimetric (2D) form and submitted in raster format. Hence, there is a need to consolidate the IT systems and introduce an automated processing system based on digital data submission. Intelligent data in 3D should be submitted and captured in our GIS system. Going forward, a high level strategic plan of moving towards a “Smart Cadastre” was initiated to set the vision and goals for the improvement and development for a cadastral survey system in the next 4 years. The 3D component will be a major feature in the strategic plan. This paper describes our idea of “Smart Cadastre” and the approach to achieve the vision. The components identified to develop a cadastre system which is “smart”, that will support and incorporate 3D parcels, will be examined

Initial Design to Develop a Cadastral System that Supports Digital Cadastre, 3D and Provenance for Singapore

It is challenging to design and develop a cadastral system that supports digital cadastre, 3D and provenance. Digital cadastre encodes cadastral information in digital format like LandXML, which allows for automation and returns high productivity. 3D enables capturing and representing the third dimension, which is critical for the development in both above and below the earth surface. Provenance allows the management of cadastre through lifespan. This is important in cadastral investigation and analysis for being informed how a cadastral parcel is being evolved over certain time period. The paper discusses the initial design of a new cadastral system called Cadastral Survey Management System (CSMS). The paper shares the SG LandXML, a Singapore profile of LandXML, which is designed based on the ICSM’s ePlan model, which in turn has been implemented in Australia and New Zealand. SG LandXML will consolidate the existing forms and data in different formats and to facilitate automation. By having a pre-validation mechanism at the Registered Surveyors’ (RS) Web Portal, the submissions by the surveyors through the Portal can be checked upfront before the authority’s inspection and approval. This will reduce turnaround times and speed-up the overall approval process. The fundamental of the system is the cadastral data model, which is designed based on the ISO 19152 - Land Administration Domain Model (LADM). The notion of BeginLifeSpanVersion and EndLifeSpanVersion in LADM has been adopted to design the provenance framework for the system. With the framework, every parcel when it is first submitted to the system will be date-stamped and the changes to the parcel will be captured for the parcel’s entire lifespan. This will allow the system to retrieve a parcel from its inception and to compare its changes over times. The paper also demonstrates some preliminary investigations on how different types of parcels, both 2D and 3D, can be integrated based on the notion of Level of Details from city modelling. The paper proposes methods how different types of parcels can possibly be encoded in SG LandXML to support 3D Cadastres

Semantics-based Fusion for CityGML and 3D LandXML

For any developments that require spatial data, often the fusion of diverse spatial datasets is unavoidable. For instance in developing a 3D cadastral database serving various purposes, data may need to be sourced from different spatial datasets such as: building design models in BIM (Building Information Model) format, topographic and built environment information in CityGML, and cadastral legal boundaries in LandXML. Syntactically and systematically this is not difficult provided the formats of datasets involved are open and are XML-based, but the fusion becomes non trivial when semantic heterogeneity occurs between schemas for example between LandXML and CityGML. This paper proposes a semantics-based fusion framework to integrate CityGML and 3D LandXML. The paper adopts the ePlan conceptual model, which is implemented in LandXML in Australia and New Zealand. Compared with the standard LandXML schema, the ePlan model is comprehensive to represent specifically cadastral survey information. The ePlan model is integrated with the Building module of CityGML through the LADM OWL Ontology. In previous research, ISO 19152 Land Administration Domain Model (LADM) has been formalized in Web Ontology Language (OWL). To integrate 3D LandXML and CityGML, this LADM OWL ontology is extended with new concepts: Physical Space Building Unit and Physical Space Utility Network and new relation: hasLegalSpace. Every concept in OWL ontology has a unique URI (Uniform Resource Identifier). The URIs of Physical Space Building Unit and Legal Space Building Unit from the LADM OWL ontology are respectively referenced by CityGML’s ExternalReference element and LandXML’s DocFileRef element. The proposed framework attempts to integrate not only the semantic models inherent in the schemas but also the geometries from CityGML and LandXML. Through this semanticsbased fusion, it is expected that a computer system will be able to do reasoning and inference in the OWL ontology. The computer system will also be able to retrieve the geometries of building unit’s legal space or physical construct, or both, through the ExternalReference and DocFileRef elements. The objective of the framework is to preserve the best of all worlds without changing the existing schemas. Although the framework is a preliminary study and no operational implementation has been done so far, this paper hopes to provide a useful reference in discussing the future directions and harmonization of the schemas