OR/14/072 Current methods for delivering geological model data
|Kessler, H, and Dearden, R. 2014. Scoping study for a Pan-European geological data infrastructure: D 3.4: technical requirements for serving 3D geological models. British Geological Survey, OR/14/072.|
The data exported from geological models can be shared in the standard formats discussed in Section 4. Commonly however, geological models are shared in other ways to facilitate viewing or analysis of the data. Table 3 highlights some of the methodologies currently being used by surveys to deliver 3D geological models.
|Synthetic sections, boreholes, slices (images and contour plots)|
|Standalone interactive viewers|
|PDFs (2D and 3D)|
|Web portals (2D)|
|Web portals (3D)|
Whilst geological models are inherently three-dimensional, it is commonly 2D outputs that are most useful for decision making. This is largely because understanding the detail in a 3D model is challenging and geologists have traditionally used, and are comfortable with, 2D cross sections and maps. Many of the delivery approaches therefore use a combination of both 2D and 3D methods for delivery. The main approaches being used in Europe are described below.
Synthetic sections and boreholes
Almost all geological modelling software packages allow the export of synthetic cross sections and boreholes from models. For delivery purposes, these outputs can be simply saved as images in standard formats (e.g. Figure 4). It may be helpful if such images are georeferenced, but they are typically just inserted into reports.
Desktop interactive viewers
Users of geological models often do not have the proprietary software within which the geological models were originally created, but they may still wish to benefit from the visualisation and analysis capabilities of the software. For this reason, a number of desk-top interactive viewers have been developed, which allow model analysis, but not model building or editing. These viewers are sometimes provided by software companies and a charge is made for their use. Sometimes this charge is paid by the survey that created the model, with the data being encrypted within the viewer to prevent unauthorised use of the viewer with other model data. Such viewers allow the user to view maps and 3D visualisations of the model, and generate cross sections, horizontal slices and boreholes. Examples of these viewers include the INSIGHT GmbH Subsurface Viewer, which is used by Flanders GSO and TNO (Figure 6). The British Geological Survey use a similar viewer, also supplied by INSIGHT GmbH and a specialist software, GeoVisionary (http://www.virtalis.com/geovisionary/). The latter allows the integration of very large volumes of data from multiple sources, allowing a greater understanding of diverse spatial datasets (Figure 5).
A number of free desktop interactive viewers are also available, for example ParaView (Figure 8) and Geocando. In addition, Google Earth can display 3D data (Figure 7), however it doesn’t represent the subsurface with true Z-coordinates.
Whilst free interactive viewers are good; they often have too much functionality, which novices find confusing. Paraview is an open source software and can be customised for geological purposes. An example is GVS, Groundwater Visualisation Software (http://www.qut.edu.au/research/research-projects/groundwater-systems-research) shown in Figure 9 (Queensland University of Technology in Brisbane, Australia).
PDFs allow the user to interact with models in 3D. They do not enable the user to generate sections and other realisations from the model, but pre-set outputs can be incorporated within the document for users to view. This method of delivery is particularly suitable for educational and marketing purposes, as they are easily deployable and can be customised to include text.
Examples are available from LBEG http://nibis.lbeg.de/cardomap3/?TH=3DPDF and BGS http://www.bgs.ac.uk/research/ukgeology/assyntCulmination.html.
Web portals provide access to, and analysis of, 3D geological models online without the need to download software. Almost half of the surveys questioned in the survey have access to such a portal. Portals vary in sophistication from allowing purely 2D visualisations (e.g. cross sections) to be generated from a map interface, to allowing both 3D visualisation and query functions. The 2D and 3D viewers currently in use are described below.
Web portals (2D)
- Groundhog viewer
The Groundhog viewer provides a 2D map interface from where cross sections (Figure 10), horizontal slices and synthetic boreholes can be generated. The viewer queries binary grid files derived from the 3D geological model.
TNO models are disseminated through the DINO-portal (www.dinoloket.nl) in a number of ways, including in an online map viewer with the option to create virtual boreholes and vertical cross-sections through the models, and as a series of downloadable GIS products. The 3D geological models are downloaded as pre-processed geo-referenced items directly from a document management system as a series of grids in case of a layer-based model. Depth and thickness maps can be viewed directly online calling a map server. The virtual boreholes and vertical cross-sections are visualized through a Java-based sampler and renderer, developed by TNO. For fast sampling these 3D models are internally stored in netCDF format. (http://en.wikipedia.org/wiki/NetCDF)
- North West German Tectonic Atlas
The State Geological Survey of Lower Saxony in Germany (LBEG) has served the North West German Tectonic Atlas via their internet portal. The application enables synthetic sections and borehole prognoses to be generated. Figure 13 shows a cross-section within the portal. Note that the section displays lines and not coloured panels, which is because the underlying model comprises individual surfaces and is not a spatially complete model stack. Such information is important to convey by linework attributes or in the metadata.
- GeORG Project
The geological models created as part of the GeORG project are served as grids and are accessible via a web portal. The data portal (Figure 14 and 15) allows the user to specify vertical and horizontal sections. The GeORG section view also displays the isotherms of a 3D temperature model and is currently the only viewer known in Europe that accesses and displays results from a property model in conjunction with the geology. The horizontal slice (Figure 14) displays how well the model is constructed, as the fault network displays sensible structures in a randomly chosen slice — something that is not trivial to achieve.
Web portals (3D)
There are three projects in Europe investigating and developing 3D web portals.
Examples of 3D web portals include:
The GeoMol viewer is developed by Giga using WebGL technology. It allows points, lines, triangulated surfaces and tetrahedron networks to be displayed directly in a web browser. http://tu-freiberg.de/fakult3/IS4GEO/gOcad2011.pdf The GeoMol project is described in section 3 of this report.
- Brandenburg 3D modelling project
The Brandenburg 3D viewer (Figure 16) also uses WebGL technology and displays TINS, lines and points within a web browser. It uses x3dom technology.
- The EarthServer Initiative
EarthServer is an EU funded initiative that attempts to establish open access and ad-hoc analytics on extreme-size Earth Science data. The BGS has developed one of the EarthServer’s lighthouse applications serving a geological model from Glasgow (UK) using WebGL technology (Figure 17).
The future of delivery of geoscience data will inevitably move to mobile technologies. Once the 3D model data is web-based, it is relatively easy to develop access to models through mobile applications, Figure 18 shows the BGS Groundhog viewer deployed on a smartphone from where the user can generate a PDF for onward use.
The arrival of Google glass and similar devices will literally open up the possibility of ‘seeing’ into the ground revealing the models and their properties, research is in the early stages in this area.
A very good example of a intuitive mobile 3D app has been developed and deployed by the Estonian Geological Survey. The app allows the visualisation and analysis of their national model the app is free and downloadable here: https://play.google.com/store/apps/details?id=com.Nortal.GeoMudel2