Towards Precise Metadata-set for Discovering 3D Geospatial Models in Geo-portals

Abstract

ABSTRACT:Accessing 3D geospatial models, eventually at no cost and for unrestricted use, is certainly an important issue as they become popular among participatory communities, consultants, and officials. Various geo-portals, mainly established for 2D resources, have tried to provide access to existing 3D resources such as digital elevation model, LIDAR or classic topographic data. Describing the content of data, metadata is a key component of data discovery in geo-portals. An inventory of seven online geo-portals and commercial catalogues shows that the metadata referring to 3D information is very different from one geo-portal to another as well as for similar 3D resources in the same geo-portal. The inventory considered 971 data resources affiliated with elevation. 51% of them were from three geo-portals running at Canadian federal and municipal levels whose metadata resources did not consider 3D model by any definition. Regarding the remaining 49% which refer to 3D models, different definition of terms and metadata were found, resulting in confusion and misinterpretation. The overall assessment of these geo-portals clearly shows that the provided metadata do not integrate specific and common information about 3D geospatial models. Accordingly, the main objective of this research is to improve 3D geospatial model discovery in geo-portals by adding a specific metadata-set. Based on the knowledge and current practices on 3D modeling, and 3D data acquisition and management, a set of metadata is proposed to increase its suitability for 3D geospatial models. This metadata-set enables the definition of genuine classes, fields, and code-lists for a 3D metadata profile. The main structure of the proposal contains 21 metadata classes. These classes are classified in three packages as General and Complementary on contextual and structural information, and Availability on the transition from storage to delivery format. The proposed metadata set is compared with Canadian Geospatial Data Infrastructure (CGDI) metadata which is an implementation of North American Profile of ISO-19115. The comparison analyzes the two metadata against three simulated scenarios about discovering needed 3D geo-spatial datasets. Considering specific metadata about 3D geospatial models, the proposed metadata-set has six additional classes on geometric dimension, level of detail, geometric modeling, topology, and appearance information. In addition classes on data acquisition, preparation, and modeling, and physical availability have been specialized for 3D geospatial models.

Fossils in a Digital Age

“…Although digital libraries hold the power to create an easily accessible repository of fossil data, removing geographic barriers, and preserving the integrity of fossils, such a library poses unique problems due to the nature of the data. These problems include how to catalogue, acquire, and preserve the data in addition to how to protect the rights of those who create and own the data (Berquist et al, 2012;Boyer et al, 2017;Davies et al, 2017;Hardesty et al, 2020;Skinner et al, 2013;Ulguim, 2018;Zamyadi et al, 2013). Literature about previous and existing digital fossil libraries, and similar digital libraries containing 3D data, provides important insight into how to create, maintain, and grow a repository of 3D fossil data moving forward.…”

A metadata ADE for CityGML

“…Additionally, Biljecki et al [4] found that the modelling choices made by practitioners when acquiring, processing and utilising 3D city models are rarely documented in the metadata of a dataset, often because there is no way to store this information. This information is necessarily not only for dataset discovery but also to ensure interoperability between various 3D city models [26].…”

“…The ease comes from reducing the need for data users to individually parse every file they encounter. Zamyadi et al [26] state that metadata for 3D geoinformation is very different from one online portal to another and even for 3D datasets within the same portal. Furthermore the integration of 3D datasets within traditional 2D portals is difficult because 2D portals do not contain specific and common metadata categories and attributes required by 3D datasets [26].…”

“…Table 1 is therefore suited to act as the base schema. Base schemas can also promote the integration of 3D city models into larger 3D geospatial catalogues, where there are already difficulties in standardising base terminology without introducing the full suite of values [26]. D The exclusion of a given category or element does not prevent their usage within our ADE as it is modularly designed for future possible extensions, as will be described in "Extendability" section.…”

“…These are summarised in Table 3. Note that the need to store the datasets used in acquisition and reconstruction as well as the model generation method [8,26] is supported by the ISO element Lineage as described in the next section.…”