Draped to Level Upward Continuation

The GM-SYS 3D Tools > Upward Continuation > Draped to Level option (GMS3VUP GX) performs an upward continuation a potential field anomaly grid measured on a "draped surface" defined by an elevation grid (e.g., gravity data measured on the topographic surface or a draped aeromag survey) to a constant elevation (flat) elevation.

This GX may only be used for upward continuation. It will terminate with an error if any part of the original elevation grid is above the new constant elevation.

Upward Continue - Draped to Level Options

Input anomaly grid (draped)	Input variable-level (draped) gravity or magnetic grid.
Observation elevation grid	Elevation grid where anomaly data were measured relative to sea level (+ up). Elevations must be in same units as grid horizontal units.
Output anomaly grid (level)	Upward-continued anomaly grid at target draped elevation.
Target elevation	New constant elevation for observed data relative to sea level (+ up). Must be greater than the maximum of the Observed Elevation Grid.
Number of levels (<100)	Number of intermediate levels used in upward continuation process. Max is 100; min is 2.

Application Notes

All input grids must be coincident (i.e., dimensions, cell size, and locations must match) for Draped to Level Upward Continuation to work correctly. This GX uses the "chessboard" method described by Cordell (1985)¹. The chessboard method interpolates between a number of intermediate parallel surfaces in order to estimate variable surface-to-level continuation. The intermediate parallel surfaces are computed using the standard MAGMAP upward continuation filter.

Reference