Overview of TcLight
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Program to compute terrain effects on gravimetric quantities.
(for detailed description see the paper : L. Biagi and F. Sanso', "Tclight: a new technique for fast rtc computation" IAG Symposia 123, pp. 61-66,
2001)
Terrain effects may be computed in two different ways:
-Direct topographic effect of all masses above the sea-level, assuming the density to be costant.
-Gravimetric terrain correction (effect of topographic irregularietes with respect to a bouguer plate).
The computation is based on a single detailed digital elevation model.
The computation may be done on a set of sparse points or for all the masses in a given area.
The input grid must be in standard format, i. e. stored rowwise from N to S, the first row must contain the header of the grid (i.e xmin, xmax, ymin, ymax, deltax, deltay). The grid must be complete, i. e. unknown height are not accepted.
The source code is mostly written in C language, with the only exception of isml.f routines.
A makefile is prepared, that contain all the parameters for compilation.
Use the unix command 'make' that launch the 'makefile' and produce the executable code
interactive input required:
See numerical example in inputTclightgrid.pdf or inputTclightpoints.pdf
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-REMOVE Procedure or RESTORE Procedure (1-2) ?
1) compute gravity disturbance [mgal]
2) compute geoid ondulation [m]
-INPUT DTM FILE:
file containing the digital elevation model.
-TC ESTIMATES ON GRID OR SPARSE STATIONS (1-2) ?
1) compute TC over the whole Dtm grid.
2) compute TC over a set of sparse points
if 2):
-INPUT FILE CONTAINING STATION COORDINATES:
file containing the coordinates of the sparse points (X,Y,Z)
-STATION HEIGHTS: FROM FILE OR BY DTM INTERPOLATION (1-2):
if 1) are used heights from the abve (X,Y,Z) file, and:
-STATION: FLOATING OR DTM STRETCHING TO STATION FILE HEIGHTS (1-2)
-MIN DIST BETWEEN COMPUTATION STATIONS AND DTM BOUNDARIES (M):
-TERRAIN DENSITY (GR/CM**3):
-APRIORI E0:
limit of the inner domain, separated from outer domain (if =0 is computed by tclight).
if 0)
-MAX VARIOGRAM VALUE FOR INNER DOMAIN DEFINITION:
-MAX RADIUS FOR VARIOGRAM SEARCHING:
-BILINEAR INNER INTEGRATION: PRISM NUMBER (ODD):
number of prisms for computing terrain effect in the inner domain
-RADIUS FOR USING AVERAGED DTM IN OUTER INTEGRAL COMPUTATION (0: NO AVERAGE):
- NUMBER OF NODES FOR DTM AVERAGE:
Radius and number of nodes to compute a coarse DTM to estimate TC in the outer domain
-COMPLETE TOPOGRAPHIC CORRECTION OR WITHOUT BOUGUER PLATE (1-2) ?
1)compute the direct topographic effect of all masses above the sea-level, assuming the density to be costant.
2)compute the gravimetric terrain correction (effect of topographic irregularietes with respect to a bouguer plate).
-FFT COMPUTATION: ZERO PADDING (0.5