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Tools for 3-dimensional geological layers models generated in spatial database using CGAL library

Lisowski P., Lupa M., Kniotek M., Piórkowski A.

Geology, Geophysics and Environment

2014

Vol. 40, no. 1

98--99

Spatial databases are commonly used to generate 2-dimensional (2D) and 3-dimensional (3D) topographic models. Mentioned models sometimes also contain information about geological layers. In that case, analysing data provides extra benefits and facilities that are desirable in presentation of complex and multilayer data (Chrobak 2009, Gotlib 2009). The possibility of storing and processing the geometry, which is saved in a standardized vector form, is the greatest advantage of spatial databases. The standards (technical documents that detail interfaces or encodings) were presented by Open Geospatial Consortium (OGC) (Open Geospatial Consortium 2014). Geometry of the objects is presented as points, lines, polygons and theirs collections. The standards also include specification about 3D data representation.Those data could be used to describe and create geological models. Another advantage of spatial databases is the possibility of adding own extensions without recompilation of all database source code. The extensions are added as a compiled library with functions, which could be written in a selected programming language (Bac-Bronowicz 2010, Lupa 2012, Lisowski et al. 2013). This paper focuses on the possibility to extend PostgreSQL database using functions that are written on the base of open source Computational Geometry Algorithms Libary (CGAL) project (Aptekorz et al. 2012, CGAL 2014). The extension library contains algorithms that are used in computer graphic and visualization of geometric data. The library was written in C++ language according to the objective-programming paradigm. Presented solution adds function of Delaunay triangulation, which is not implemented in PostGIS (Lisowski et al. 2013). This tool allows to generate Triangulated Irregular Network (TIN) surfaces of geological layers in a simple and functional way. 3D terrain model is created using information from spatial database (2D and 3D objects). In the next step, TIN model is generated, which approximates the modelled geological layers by a network of the triangles (tangent edges). Interoperability and unified data edition was achieved due to using of triangles (represented by triangles which are polygon type, vanished points and lines objects). Nevertheless, generating of 3D models from 2D data with parameter, which would properly represent a surface and terrain layers, is not a trivial task.

Modele rzeczywistości geograficznej a modele danych przestrzennych

Głażewski A.

Polski Przegląd Kartograficzny

2006

T. 38, nr 3

217-225

Artykuł jest próbą uporządkowania pojęć funkcjonujących na pograniczu informatyki i kartografii (w większości zadomowionych w otoczeniu systemów informacji geograficznej), które stanowią informatyczny, a zarazem kartograficzny opis rzeczywistości - pojęć definiowanych z punktu widzenia kartografa.

The article attempts to classify the terms concerning the modeling of spatial data functioning in the environment of systems of geographical information, which are both digital and cartographic description of geographic reality. In the first section models of spatial data, as elements of models of IT systems concerning space (GIS) are differentiated from database models and models of knowledge, which are independent elements external to system models (fig. 5). The article defines database models and presents their development towards the integration of tools serving the database spatial element with the standard database management system (DBMS). The categories of geographic reality models which are characterized most widely are those useful for modeling of objects and spatial phenomena with IT systems, particularly GIS. These models are characterized according to the criteria of their perception and interpretation. Two major categories should be mentioned here: mental models, which are created in reader's mind and digital models, which appear mostly in digital form. They should be treated separately from dafa models, although some categories of geographic reality models make sense only through certain spatial data models. The article presents features of the above mentioned model categories and provides examples of data sets belonging to them. Mental models are created in reader's mind as a result of his own experience under the influence of direct perception of geographic space. Material models can have three forms: - Topographic model (database), a.k.a. Digital Landscape Model (DIM) - Cartographic model (sign), a.k.a. Digital Cartographic Model (DCM) - Teledetection model (picture), a.k.a. image model. Topographic model contains information on spatial objects (phenomena), the location of which has been established with coordinates of selected reference area. It is characterized with strict georeference, which results in precise preserving of topological properties of objects and creation of unique data structures during its implementation. This model best represents spatial relations between objects and can be the basis for spatial analyses conducted with the use of digital techniques. Cartographic model - (sign) conveys information about objects (phenomena) using fixed graphic conventions - a system of cartographic signs, which are the medium of geographic information. It is a representation of geographic space prepared for direct perception by human senses. Topological features of represented objects are preserved indirectly - they can be read through the method of image interpretation (fig. 9). Teledetection model, often referred to as image model, is a model of geographic reality, which conveys the picture of the area automatically recorded in various ranges of electromagnetic spectrum. In this case object classification of information does not apply, so object classes and their attributes can not be directly modeled. A pixel is a medium of information. Air photos and satellite pictures are examples of such models (fig. 10).