2018-03-30 12:04:14 +02:00
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function [Az, El, D] = topocent(X, dx)
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% TOPOCENT Transformation of vector dx into topocentric coordinate
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% system with origin at X.
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% Both parameters are 3 by 1 vectors.
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%
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% [Az, El, D] = topocent(X, dx);
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%
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% Inputs:
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% X - vector origin corrdinates (in ECEF system [X; Y; Z;])
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% dx - vector ([dX; dY; dZ;]).
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%
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% Outputs:
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% D - vector length. Units like units of the input
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% Az - azimuth from north positive clockwise, degrees
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% El - elevation angle, degrees
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% Kai Borre 11-24-96
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% Copyright (c) by Kai Borre
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%==========================================================================
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dtr = pi/180;
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[phi, lambda, h] = togeod(6378137, 298.257223563, X(1), X(2), X(3));
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cl = cos(lambda * dtr);
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sl = sin(lambda * dtr);
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cb = cos(phi * dtr);
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sb = sin(phi * dtr);
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F = [-sl -sb*cl cb*cl;
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cl -sb*sl cb*sl;
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0 cb sb];
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local_vector = F' * dx;
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E = local_vector(1);
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N = local_vector(2);
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U = local_vector(3);
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hor_dis = sqrt(E^2 + N^2);
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if hor_dis < 1.e-20
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Az = 0;
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El = 90;
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else
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Az = atan2(E, N)/dtr;
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El = atan2(U, hor_dis)/dtr;
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end
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if Az < 0
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Az = Az + 360;
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end
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D = sqrt(dx(1)^2 + dx(2)^2 + dx(3)^2);
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%%%%%%%%% end topocent.m %%%%%%%%%
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