The concept of spatial representation of data is very frequently used in modern cartographic works. It is applied for general presentation of space, or presentation of some particular geological or geographical and other subjects, as well as presentation of a particular image (model) of a selected part of reality. Talking about space in our presentation for other people, we consider an image, a sketch, a drawing or a map showing three basic parameters, usually represented by X, Y, Z.

Classic cartography applies presentation based on two parameters X, Y or longitude and latitude with added altitude measure Z, shown as contour lines. Currently the third parameter of altitude measurement is represented by shaded texture, replacing poorly spatial representation of contour line gradient of selected colours, with a degree of grey emphasising altitude differences. It is a certain simplification of reality represented on a flat surface of a paper sheet or a monitor screen, with prescribed spatial features. Nowadays, images with X, Y parameters are called 2D and the ones using three parameters 3D.

In fact, our representations are all the time in two dimensional space (X, Y), hence, when showing full space we usually talk about 2.5D The notion is to distinguish our representations e.g. spatial models, which still remain on a 2D flat space e.g. a sheet of paper. Unfortunately space visualisations in many cases, when applying contemporary technique of images, must remain flat, with space being only simulated by certain procedures (shading, stereoscopic images, linear perspective drawing etc.), which should be called 2.5D. GPS images, topographic maps, geological maps, an image of a space sector etc. are represented on a flat image, however, 3D space elements, with a time coordinate added sometimes to the presented phenomena, occur there. Possibly, in a few years a portable laser projector or another 3D one might be a breakthrough. Then, instead of using a sheet of paper to explain a spatial problem, like today, a portable projector will be used to show a real 3D image to our interlocutor. For now, flat 2.5D images and our imagination put together must be enough to create a vision of a geographical, geological or purely virtual space.

From the GEOLOGICAL research point of view, 2.5D visualisation seems to be one of the crucial points in research methods and the ways of presentation of the research results, therefore, it has become an important stage on the way of development to a full 3D or even 4D (time is an important factor in geology) representation.

Up till now, a map has been a model of forms and geological objects, where the most important element is a good intersection drawing and distribution of spatial elements on the map chart in 2D. Replacing the drawing by 2.5D and in future by 3D digital models creates new possibilities in geological research, enabling to prepare a digital (full 3D) model of the geological structure.

Introduction of a surface numeric model of relief to geological cartography, represented in 2.5D convention (DEM, DTM, SRTM) to visualise the geological structure enables to develop new research techniques in geology. Digital models will allow better understanding of geological structures and will inspire development of working hypotheses. They will also help to relate geological structure to morphostructural geoenvironmental elements and to apply the concept of spatial penetration of rock formations.

Currently collected data DEM, DTM, SRTM, etc. offer vast possibilities to work with 2.5D images, often applied for various needs in space representation. Appearing tasks in reambulation of geological maps give an opportunity to enrich their contents by more legible elements of relief and 2D forms connecting an image of the geological structure with a numeric model and satellite images. Modern digital methods applied to make a detailed geological map of Poland and digital processing of images offer new possibilities to use visualisation techniques in geology, including 2.5D and 3D. Digital methods of processing of geological structure models provide multi-dimensional and multi aspect research possibilities, which goal is to simplify solving, understanding and presentation of geological problems, as well as the other ones.

by J. Nita

More about 2D and 2.5D maps made in the Department of General Geology, the University of Silesia can be found on the sub-page Projects and web pages of PrzeglÄ…d Geologiczny[1], [2]