Densities

bouguer

The program estimates the densities of the topographic masses according to the oldest method of this type (Bouguer, 1749). Unfortunately, although we slightly modified the method, it still does not result in correct output densities. This is why we consider the program as an auxiliary one and thus suitable for testing only.

correction-density

Similarly to the previous case, this program was intended as a testing device for the existing methods of topographic density estimation (Nettleton, Jung, Parasnis, plus some modifications and combinations of those procedures).

find-geol-code

This is important program which enables the user to assign the SHP polygon determining an area in a map to a point with arbitrary coordinates x and y (e.g. a geological unit in the Geological map of the Slovak Republic 1:500000 to a gravimetric point in the Gravimetric database of the Slovak Republic, GDBSR).

grid-residuals

This is again a testing program. Its objective is to show how the grid residuals in a specific GDBSR point or points would look like if the point(s) in question was or were excluded from the gridding process.

griffin

This program was written according to an old algorithm (Griffin, 1949) which we slightly modified. We have used it for calculations of one type of residuals of both the Free-Air Anomalies (rFAA) and Near Topographic Effects (rNTE). Those residuals were subsequently tested from the aspect of their mutual proportionalities.

h32w

This program is instrumental to the analysis of the linear tendencies which are intrinsic to the gravity data. The background of the method has been described in the contribution of Mikuška et al. (2012, SEG Expanded Abstracts). From the aspect of their mutual proportionality (that proportionality is important when interpreting densities), the output values of rFAA and rNTE proved to be the most suitable.

hv32w

Like the previous program, also hv32w is intended for the analysis of the linear tendencies which are intrinsic to the gravity data, but this time it is realized in 3D space, while h32w is working in 2D space (Mikuška et al., 2012, SEG Expanded Abstracts). However, from the important aspect of their mutual proportionality, the residuals calculated by hv32w turned out to be not as good as those calculated by h32w or griffin, what we consider as paradox.

inflection-mtk

In the framework of development of our new method for correction density estimation, we first attempted to delineate manually the residuals rFAA and rNTE, respectively. This program was originally intended as a substitute of such manual procedure but, unfortunately, we have found that a single computer program can not successfully replace the manual delineating. This program can thus serve only as instructive one.

linfit

The most important outputs of this program are the parameters of approximating polynomials of degrees 0 to 9 within circular moving window which successively centered into the individual points of their input collection. There are also other statistical parameters calculated from the subsets within each calculating window.

Geological correction

crust1-topo

This program calculates global denstity estimates of the Earth topographic masses on one side and the Earth crust on the other, according to the CRUST1.0 model data.

crust1-topo-volume

It represents an extension to the previous global denstity estimations of both the Earth topographic masses and the Earth crust, according to the CRUST1.0 model data, but this time it s based on the weighted averages of the model densities using weights proportional to the approximate volumes of the model rock units in question.

topo-2-airy-depth

The program serves the purpose of calculating the (hypothetic) geometry of the Moho discontinuity based on the Airy-Heiskanen isostatic hypothesis. The input information is represented by a grid of the global relief . The Earth crust density, density contrast at the crust/mantle boundary and selected depth to the Moho discontinuity along the coastline, respectively, are required as calculating parameters.

vz5-crust

It is the most important program unit. It calculates gravitational effects of the individual Earth crustal "layers" as they are represented by the CRUST1.0 model, considering the Earth curvature, using the spherical approximation. The inputs are following: the calculation points locations on the Earth surface (longitude, latitude, point number and its height with respect to the approximation sphere), grids of the individual model boundaries, model densities (they can be given either as constants valid for the whole "model layer" or as quantities varying along the globe in the form of density grids). The maximum number of layers is sufficient for simultaneous calculating the whole Crust1.0 model. The user can select the interval of the angular distances from and to which the model volumes are taken into consideration, with possible options like "the whole Earth, from the calculating point to the antipodes" or "arbitrarily selected angular distance zone". The outputs are the calculated gravitational effects with estimation of their vertical gradients (the gradient estimation is optional).