Troubleshooting GravMag

Q: When I open GravMag from the CD on a Windows computer, the body I've added and the original section window are all wrong.

A: For a mysterious reason we have not understood, when launching directly from the helper application on the CD from Windows, GravMag gets an internal constant reset. Solutions are (1) launch using Windows Explorer and not the helper application, (2) to reset the left and right window bounds (in the Section Window), add a new body in the Model Window, and then delete the original body, or (3) open a saved model to work from. Since later versions are updated on a hard drive, this should not be an issue in running these versions of the software.

Q: I have selected Gravity (or either magnetics option) from the View Menu and I have bodies to model but do not see the gravity (or magnetics) profile on the Section Window.

A: Open the appropriate Data Window. The Section Window only displays a profile when a Data Window is open.

Q: Why can't I open the Magnetics (or Gravity) Data Window?

A: These windows are only accessible when you have selected to view that field from the View Menu. Once the appropriate option is selected, the data window is accessible through the Window menu.

Q: I input raw magnetic field measurements into the Magnetics Data Window and then clicked the Use Mean Offset button; all of my data values (and the anomaly) became the same number!

A: The Earth's magnetic field is usually much stronger than observed variations. The default number of significant digits shown is 3, which means variations under 100 nT are not visible; change this from the Preferences window to 5 or 6 to see your data properly.

Q: I would like the bounds of the data plots in the Section Window to remain constant. Can I do that?

A: Not directly (except for the cross section, whose bounds are set in the Section Window). However, if you want to see all the data, you can add two extra points to the relevant data window and set the observed value of those points to the maximum and minimum you want displayed.

Q: I entered my data points in the data window but do not see them on the Section Window.

A: Most probably you did not adjust the right and left bounds on the plot (in the Section Window) to include your points. Pressing the Show All button will quickly remedy the problem.

Q: In the cross section pane of the Section Window, I cannot move the currently selected body (or point) with the arrow keys.

A: Probably one of the bounds edit fields (where you set the left, right, and bottom of the view) is currently selected. Clicking on the cross section pane (or tabbing until nothing appears to be selected) will allow you to use the arrow keys to move selections.

Q: My gravity anomalies seem far too large or have the wrong polarity.

A: You should check that you have input the difference in density between your body and the surroundings rather than an absolute density. For instance, valley fill might have a density of 2.3 g/cc which, if entered as the density of a body, yields a gravity high rather than the expected low. Instead the density contrast with the surrounding basement rock should be used. Thus if basement is 2.8 g/cc, a density of -0.5 g/cc should be used for the body representing the valley fill.