OR/18/010 Introduction

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Terrington, R L, Thorpe, S. 2018. Post-calculation checks of GSI3D Models V2. British Geological Survey Open Report, OR/18/010.

An important part of the model checking process is done in post calculation. This allows you to see whether the 2D and 3D distribution of geological has been calculated correctly. This is very important when making volumetric calculations and assessing the distribution of these units. Please refer to the GSI3D 2011 manual (Mathers et al 2011[1]) for related information regarding the checking of models.

All of the cross-sections in section 2 have been generated from calculating the model and looking at the synthetic outputs from the calculation. The snapping functionality has now made some of these problems easier to avoid but for older models or models that pre-date this functionality the following checks should be made to improve the calculation of the model and the surface triangulation, and the resulting surfaces generated.

Before checking the model, you must calculate it by doing the following: calculate – nonfaulted – calculate all units from sections and envelopes

Once the model has been calculated do the following to view the ‘calculated’ or synthetic output of each of the existing sections: right click in the cross-section window – window properties – click off polygons under correlated section rendering – click on polygons for synthetic section rendering (Figure 1).

The next stage is to go through every cross-section to see if any of the calculated units are missing/have a spiked triangulation or have a peculiar geometry compared to the original correlation lines. In the following pages there are examples of the kinds of issues to look for in post calculation and how to remediate these to improve the calculation of the units.

Figure 1 Setup for checking calculated sections in cross-section.


  1. Mathers, S J, Wood, B, Kessler, H. 2011. GSI3D 2011 software manual and methodology. British Geological Survey Open Report, OR/11/020.