earth science

GeoModeller

GeoModeller is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand GeoModeller rather than just read about it. In short: GeoModeller (old names include 3DWEG, Geomodeller3D) is a methodology and associated software tool for 3D geologic modelling developed by Bureau de Recherches Géologiques et Minières and Intrepid Geophysics over the last 20 years. The software is written using Open CASCADE in C++ for the engine (geometry, topology, viewers, data management, ...), Java for the GUI and data are stored in extensible mark-up language XM…

Key takeaways

GeoModeller belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect GeoModeller to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of GeoModeller from memory before moving on to harder problems.

Reference excerpt

GeoModeller (old names include 3DWEG, Geomodeller3D) is a methodology and associated software tool for 3D geologic modelling developed by Bureau de Recherches Géologiques et Minières and Intrepid Geophysics over the last 20 years. The software is written using Open CASCADE in C++ for the engine (geometry, topology, viewers, data management, ...), Java for the GUI and data are stored in extensible mark-up language XML. GeoModeller has started to revolutionise the working practices, data standards and products of a geological survey as a whole. The software takes into account all structural geology data such as dip, dip directions, strike, hingelines and axialtrace to build the geometry of geological units.

Methodology GeoModeller utilizes a Digital Terrain Model, surface geological linework, cross-sections, geophysical interpretation and drillhole borehole data to enable the geologist to construct cross sections, or 3D models. 3D Geostatistical interpolation (co-kriging) using all the data (location of interface, dip, direction, ...) produces a 3D implicit function representing a solid model. The model build may take in account if necessary a network of geologic faults. The model could be represented by triangulated objects each corresponding to one of the geological units present. Geologists can draw the model in their sections to obtain a fence diagram. The geologist can use their knowledge to add information in the 3D space until he obtain a 'right' model.

Inversion of the 3D model In geological and mining or oil exploration applications, seismic profiles as well as gravity and magnetic data are often available. Interpreted seismic cross-sections directly provide data that can be processed directly as geometric constraints for 3D modelling. On the other hand, gravity and magnetic data provide indirect constraints. Presently, a 3D geological model is considered as the initial state of a constrained inverse modelling of this data. That inversion is based on an iterative method, which is applied to a discrete version of the domain under study. This inversion formulation allows separate inversion of either gravity or magnetic data or simultaneous inversion of both datasets and tensor components of gravity and magnetic field . The final result is a probabilistic 3D geological model.

References Lajaunie Ch., Courrioux G., Manuel L. (1997). Foliation fields and 3d cartography in geology: principles of a method based on potential interpolation. Mathematical Geology, 29, 571–584. Halbwachs Y., Courrioux G., Renaud X., Repusseau P. (1996). Topological and geometric characterization of fault networks using 3-dimensional generalized maps. Mathematical Geology, 28, 625–656. (Best paper award in Mathematical Geology, by the International Association for Mathematical Geology.) Bosch M., Guillen A., Ledru P. (2001). Lithologic tomography: an application to geophysical data from the Cadomian belt of northern Brittany, France, Tectonophysics, 331, 197–227. other articles or PhD thesis Archived 2007-08-30 at the Wayback Machine McInerney, P., Guillen, A., Courrioux, G., Calcagno, P. and Lees, T. Building 3D Geological Models Directly from the Data ? A new approach applied to Broken Hill, Australia. https://web.archive.org/web/20080718213311/http://www.geomodeller.com/ig/knowledgebase/special_topics/3DGM_BuildModelFromData.pdf

External links GeoModeller homepage old web site with models in France

Worked examples

Example 1 — a first encounter with GeoModeller

Start with the simplest possible case. Write down what GeoModeller claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to GeoModeller before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about GeoModeller ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of GeoModeller

In research: GeoModeller appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses GeoModeller in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: GeoModeller is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology software, Methodology, so understanding it makes those chapters shorter.
In everyday life: Look for GeoModeller outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study GeoModeller in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what GeoModeller means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain GeoModeller out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is GeoModeller in simple terms?

Why does GeoModeller matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study GeoModeller?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on GeoModeller.