BGS EarthServer - 3D Geological Models
Geology models are the core focus of BGS activities now and underpin a large range of applications. Geological structures are potentially complex and will often require 3D vector modelling systems rather than rectangular grid formats to represent accurately. However, in many cases, particularly with superficial deposits, 2D grids of the elevations of bounding surfaces of various formations or lithology types (and therefore also their thicknesses) are good enough to provide useful representations. We also use 3D rectangular voxel models as a basis for modelling and calculating properties of the sub-surface.
Examples of the kinds of query we would like to perform are:
- What is the thickness of a particular formation at a particular point (calculated from top and base elevations)?
- In combination with the DTM (such as above), what is the depth to the top or base of a particular formation at a particular point?
- Highlight areas where the thickness or depths are greater or less than a certain value.
- What is the vertical sequence of geology at a particular point?
- Estimate volumes of single or combined geological units over a given area.
- Create vertical geological cross-sections along given lines.
- Create geological unit coverage over irregular specified surface domains such as: horizontal plane (simple), variable elevation surface (e.g. water table), tunnel walls, cave surfaces etc.
- Create a 3D voxel model (like the one described below which was created in desktop software) from the input surface boundary grids.
The simple client demonstration uses a subset of 3D model data around the Glasgow area in Scotland. This has been converted into a number of 2D grids of boundary surface elevations and formation thicknesses and a 3D voxel model of lithology types. There are 66 2D grids for the Glasgow area. These consist of 3 grids for each of 21 different geological units representing the top surface, bottom surface and thickness of each of these units plus 3 for the top, bottom and thickness of the whole model. These are named glasgow_code_t, glasgow_code_b and glasgow_code_th, respectively where code is an abbreviated name for each unit. (The thickness layers are redundant as they can be calculated from the top and base but provided a useful double check.) You can also view the same surfaces in 3D
There is a 3D voxel model for the Glasgow area called glasgow3d_r01 where each voxel has an integer code which for the lithology type (sand, clay, etc.) We don't currently have any 3D client set up for viewing this but some simple calculations can still be done such as calculating the volumes of particular lithology types.