3D geological models

Within its research activities as well as different commercial contracts, the Czech Geological Survey deals with creation of the 3D geological models and with the definition of a unified systematic approach to their storage, administration and presentation.

As the administrator of large geoscientific datasets from the whole territory of the Czech Republic, the Czech Geological Survey is involved in numerous applied research projects dealing with various kinds of use of the underground rock environment. The recently solved issues of utmost national importance include high-speed railway tunnels, reassessment of mineral resources, assessment of geothermal energy potential, and, last but not least, location of a deep radioactive waste repository.

Overview map of 3D models

The Czech Geological Survey creates models of two types - structural geological models of rock environment of medium to large scale, and photogrammetric models of relatively smaller extent. Interactive map below shows areas in the Czech Republic that have already been modelled in 3D - by clicking on an area of interest, the user can see basic metadata about the model and its preview (or a preview of a part of the model that is not restricted for public presentation). The overview map is being continuously updated.

A new metadata profile 3DGM has been defined to ensure a unified metadata description of the models produced by CGS. The Profile is fully compatible with the INSPIRE requirements and with the international standard ISO 19115.

Structural geological models

The scarcity, heterogeneity and complexity of available archived and newly acquired geological data often do not allow for any semi-automatic techniques of model construction; the models usually need to be created purely manually. The 3D geological models (see example below) created in the Czech Geological Survey cover a broad spectrum of scales and lithotectonic environments. Concerning scale, they range from meters in the case of outcrop fracturing quantification for Discrete Fracture Network models, to regional scale covering areas of hundreds square kilometres and up to 1.5 km depth. They depict structurally complex high–grade metamorphic units that exhibit several episodes of pervasive ductile deformation, partial melting and emplacement of magmatic bodies, as well as simple overlying sedimentary formations. An integral part of the model production is also an initial assessment of model credibility, used especially for purposes of safety analysis.

Based on the 3D geological models, 3D hydraulic and transport numerical simulations are performed to estimate groundwater flow. Additionally, the models are used by engineering companies in CAD-type SW as natural limits for technical design of the underground facilities.

3D geological model describing geometry of lithologies at one of the potential HLW repository sites. Extent of the model is 12.3 x 8.3 x 1.5 km. Surface of the granitic pluton of interest (in pink colour) is removed to show its interior down to 1.5 km depth. Yellowish polygons define potentially suitable locations for the repository at ca. 500 m depth. Fault planes are not shown.

Search for unconventional and conventional energy resources and for methods, which would reduce the greenhouse gas emissions benefits from new 3D insights into sedimentary basin geology. Working with large geophysical and geological datasets is now easier and faster with software such as Petrel. 3D models visualize the architecture of sedimentary strata, sequence stratigraphic details and faults. We use them for evaluation of geological structures focused on reservoir volumes, permeability, and seal efficiency. The results serve as basis for further scenario testing of future technological actions and related environmental risks.

3D geological model of LBr-1 structure in the Vienna basin with faults, 4 reservoirs and a seal horizon built based on well and seismic data using Petrel software. The data was provided by MND and the Petrel software academic license by Schlumberger. (Author: J. Franců et al.)

Currently, SW MOVE is mainly used for the creation of the structural geological models and e.g. SW Petrel is used for the modelling of the sedimentary basins. These 3D models are visualised as 3D web scene stored in ArcGIS Online. The scene can be viewed by the standard viewer integrated in that platform.

Photogrammetric models

In addition to 3D geological modeling, which deals with modeling of the subsurface, CGS also focuses on a methodology for creating 3D photogrammetric models of the surfaces. This activity has been closely related to the introduction of UAS in the CGS´s activities and related UAS-borne data processing and visualizing needs. However, surface photogrammetric models are also created on the basis of hand-taken photographs, whether it is documentation of a surface quarry or an underground mine walls.

Photogrammetric models are generated using the Agisoft Metashape software which creates point clouds and three-dimensional objects with orthomosaics, set in geographical coordinates. This software also allows you to work with multiband spectral (multispectral) images, which are used for scientific research of monitored surfaces. These models can be viewed on the web using a tool developed in the CGS. This tool is based on the ope-source javascript library Three.js.

Photogrammetric models are used, for example, in the monitoring of rock falls at the Nechranice dam, in the monitoring and research of historical mining on the Jizerka stream, or in the reconstruction of underground mines.

The models displayed on the web are quite large (one model is about 100-200 MB) and require sufficient graphics card performance in your device (but they should also work on modern mobile phones and tablets). As this is the first demonstration of this way of displaying 3D models on our web, we welcome all your comments and observations at webmaster@geology.cz.