3.0 Creating a new model

Important

If you have not yet installed GMG, please first follow the instructions on the Installation page before continuing with the tutorial.

3.1 Defining the model profile

Our model profile runs south to north from X-X’ with a total length of 52 km. The profile start and end coordinates in British National Grid format (EPSG code: 27700) are:

X  = 393956 E 521000 N
X' = 393956 E 571000 N

3.2 Initiating a new model

Once you have opened GMG you can create a new model by navigating to the Menubar and selecting:

File -> New model...

A window for setting the model dimensions will appear. Here we wil assign the model X and Z dimensions in kilometers, as well as the increment at which the predicted gravity and magnetic anomalies will be calculated.

In this example our model profile is 52 km long spanning x=0 to x=52. We’ll set the X window dimensions to slightly exceed these bounds, as this will make it easier to view the entire model. So, go ahead and set X1=-5 and X2=55 km. We will be modelling the upper crustal structure, so lets set the Z window dimensions as -1 and 10 km and the calculation increment as 0.1 km.

Then click Create Model to initiate the model.

Note

You can always change the model dimensions and calculation increment at a later time. For example, you may start out by modelling with a coarse spacing to ensure GMG runs quickly. Then, once you are satisfied with your starting model and are ready to make fine scale adjustments to your model, you might then reduce the calculation interval.

To modify the model dimensions at anytime, navigate to:

Model View -> Modify current model dimensions...