Vertical gradients (the change in gravity with vertical position, in units of microGal/m) are typically measured by moving a relative-gravity meter between the land surface and (or) two or more positions on a tripod. Typical tripod heights are 71 cm (the height of the A-10 absolute-gravity meter) and 131 cm (the height of the FG-5 absolute-gravity meter).
If data are collected at two heights (typically, one at the land surface and one elevated, but any two heights are possible) GSadjust can calculate the vertical gradient by dividing the gravity difference by the height interval. This process requires the Roman drift method be used. The height interval is specified by the menu option Process > Vertical gradient interval... The default value is 64.2 cm; if the tripod is set to this height the sensor of a LaCoste and Romberg D or G relative-gravity meter is located at approximately the measurement height of the A-10 absolute-gravity meter.
Vertical gradients are calculated with the menu option Process > Write vertical gradient file... This opens a file save dialog. The resultant file, a text file with the extension .grd, has a single value and uncertainty (in units of µGal/cm).
At this time GSadjust will only calculate a two-point, first-order linear gradient.
