Topographic Corrections for Gravity Measurements Software - TopGrav


Description of Technology

TopGravTM is a suite of C++ language programs that computes topographic attraction and/or terrain correction for vector and/or scalar gravity measurements on land, at sea and at flight altitude. The software provides accurate values of either topographic attraction or terrain correction by using a gridded digital topgraphic model in either a mass-line or mass-prism representation. The mathematical formulas were developed at the University of Calgary, Department of Geomatics Engineering.

TopGrav uses the techniques and algorithms developed in the 1980s and 90s to achieve the best computational efficiency while minimizing the requirement on computer memory. The conventional integral formulas are expressed as a series of two-dimensional convolutions. With the use of Fast Fourier Transform (FFT), the required computer CPU time is reduced logarrithmically (by a ratio of hundreds to thousand times - depending on the size of the computational area). By using fast Hartley transform (FHT), the computational efficiency can be further improved by one-third while the required computer memory can be reduced by half.

Areas of Application
  • Geophysics and Geodesy for topographic reductions of terrestrial, shipborne and airborne gravity measurements used in gravity interpolation, geophysical interpretation and geoid/vertical deflection determination
Competitive Advantages
  • Advantage of using unified formulas that compute both topgraphic attractions and terrain corrections in land and ocean areas or coastal regions with gravity measurements taken either on the earth's surface or in space - with either constant or horizonally varying densities
  • Based on FFT/FHT methods
  • Extremely fast as compared to conventional numerical integration software
  • Suited for computations involving very large elevation/density data files
Stage Of Development

TopGrav™, coded in C++ language with object-oriented design, is easily portable to any platform and operating system, or implemented in any other user-designed software. The software is well documented through a user's manual. Detailed derivation of the mathematical formulas is also available upon request.