New Depth Model

This dialog guides you through the process of creating a new Depth model. A new Depth model consists of a single block “Crustal Rock” with a flat bottom and a topographic surface that may vary in the X-direction, but is constant in the Y-direction. Outside of the area of interest, the model is extended to “infinity” in the +/-X and +/-Y directions to eliminate edge effects.

Geologic Strike Angle

If you know the orientation of Geologic Strike, enter it here. This sets the orientation of the geologic features of your model. All 2-D and 2½-D blocks in the model are oriented in this direction. You may leave this field blank if you don't have the information and an orientation will be calculated from your input data, but it is best to supply this explicitly, whenever possible.

Define Area of Interest and Topography

You may import a topographic profile from a Geosoft Database or an ASCII file that defines the topography and your area of interest. The input (X,Y) data will be scanned to determine the location and orientation of your model. The first point in your profile will define the model origin and a best-fit line through the (X,Y) values is calculated as the default Azimuth of your model. By default, Geologic Strike is calculated to be perpendicular to this best-fit line. If you know the Geologic Strike Angle from other sources, enter it and recalculate the appropriate Profile Azimuth. The topographic profile is projected onto the vertical plane defined by the Origin and Azimuth, and is continued “infinitely” in the +/- Y directions.

For a theoretical model (i.e. without pre-existing topographic or X,Y data), enter the elevation of the top surface. You may modify this surface later as you edit your model.

Profile Origin and Projection

When using a topographic profile, the default Profile Origin is the (X,Y) location of the first point in the profile. If the profile is imported from a database, the Coordinate System and units will be read from the default X and Y channels in the database. If no Coordinate System is detected or you are importing a profile from an ASCII file, you must specify the Coordinate System and units using the Coordinate System Wizard [CoordSys] button.

If no topographic profile is supplied, you must supply the Origin and Coordinate System manually. You will not be able to create the model without this information.

Cross-Section Orientation and Limits

The Cross-Section limits define the “Startup View” for your model after it is created; i.e. the limits of your area of interest. If you imported a topographic profile, the calculated Profile X limits will extend from X=0 (the origin) to the location of the last profile point, as projected onto the model section. You may over-ride these values, or enter your own if none have been calculated.

By default, the Profile Z limits extend from 0 to 50 km, the full thickness of the initial “Crustal Rock” block. You may set the view limits differently, if you prefer.

Origin and Projection

The Azimuth of your model XXX The Cross-Section limits define the “Startup View” for your model after it is created; i.e. the limits of your area of interest. If you imported a topographic profile, the calculated Profile X limits will extend from X=0 (the origin) to the location of the last profile point, as projected onto the model section. You may over-ride these values, or enter your own if none have been calculated.

By default, the Profile Z limits extend from 0 to 50 km, the full thickness of the initial “Crustal Rock” block. You may set the view limits differently, if you prefer.

Add Anomaly Data to new model?

Check this box if you have measured Anomaly data or wish to add “dummy” calculation stations immediately. Once the model is created, the Manage Anomaly Data spreadsheet will be presented and you may add or create observation stations. Otherwise, you may access these functions from the Manage Anomaly Data spreadsheet.

Application Notes

The Geologic Strike Angle is the critical orientation for modeling purposes, because all blocks will be extended in this direction. The Profile Azimuth must be perpendicular to the Geologic Strike Angle -- “skewed models” are no longer required or supported. The Origin and Profile Azimuth are used to relate the model coordinate system to external coordinate systems (via a translation and rotation) and define the location of the Y=0 plane. For display purposes, all model elements are projected onto this plane.