Geophysical Software

Geophysical Software is a small firm focused largely upon developing application software for potential field data reduction and interpretation. At present, most applications are in the field of gravity field interpretation and data reduction, particularly in the area of high-precision, digital terrain corrections for gravimeter stations. Software permitting the user to correct gravity stations using a variety of different types of terrain data is available.

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Products and Services


Two types of gravity terrain correction software are offered. One, called InnerTC, provides terrain corrections for gravity data using the standard 30-meter Digital Elevation Models that are produced by the U. S. Geological Survey. InnerTC permits gravity terrain corrections to be made from very close to the gravity station to a distance of a few kilometers. It provides extremely accurate terrain corrections and is limited in accuracy only by the resolution and accuracy of the basic Digital Elevation Model used. The basic methodology is described in Cogbill (1990). Documentation for the routine is available here for those wishing more detailed information.
InnerTC permits one to calculate extremely accurate gravity terrain corrections, provided that the DEMs are an accurate representation of the nearby terrain. Some of the features of InnerTC are:


Because the 30-m USGS DEMs are, of course, only available in the United States, and because some users may have special, possibly very high-resolution, digital terrain models, RasterTC is offered. RasterTC permits a user to provide a Digital Terrain Model in the form of one or more terrain grids. Such grid(s) can be provided in different resolutions, permitting, for example, grids having very fine spatial resolution to be used close to a set of gravity stations, while coarser grids can be used at greater distances, thus improving computational efficiency.

RasterTC is very similar to InnerTC. Differences are primarily in the type of terrain data provided. Documentation is available here, as well.


A related product is LaserTC. LaserTC was originally designed to provide high-precision terrain corrections for topography occurring within the first 50 meters of a gravity station. Digital terrain data so close to a gravity station can now be readily acquired in the field using newly available, reflectorless laser rangefinders. Such rangefinders permit a detailed digital terrain data to be acquired in the vicinity of a gravity station within only 2-3 minutes, permitting the gravity meter operator to acquire the terrain data needed for LaserTC at the same time as the gravity measurements are made.

Although LaserTC was originally designed for use as described above, it is quite general; thus, close-in terrain corrections for gravity stations can be calculated using virtually any type of user-supplied terrain data. For example, terrain corrections can be readily calculated using topographic data consisting of digitized elevation contours. Documentation for LaserTC is available for those wishing more detailed information about how the program works.


Both InnerTC, RasterTC, and LaserTC are provided as a terrain correction package. Pricing for the package is as follows:

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Contact Information

For more detailed information regarding pricing, product availability, services offered, or future products, please contact us by telephone or e-mail:

References Cited

Cogbill, Allen H. (1990) Gravity terrain corrections calculated using Digital Elevation Models, Geophysics, 55(1), 102-106.

Lyman, Gregory D., Carlos L. V. Aiken, Allen Cogbill, Mamadou Balde, and Chet Lide (1997) Terrain mapping by reflectorless laser rangefinding systems for inner zone gravity terrain corrections, to be presented at the 67th Annual Meeting of the Society of Exploration Geophysicists, November 2-7, 1997, Dallas, Texas.

Plouff, Donald (1966) Digital terrain corrections based upon geographic coordinates [abstract], Geophysics, 31, 1208.

Copyright 2013, Geophysical Software, Inc.

Last modified 24 October 2013