%                            sgs85con.m
%  Scope:   This MATLAB macro sets the SGS-85 (Soviet Geodetic System 1985)
%           most used constants as global variables.
%  Usage:   sgs85con
%  Description of global parameters:
%           a_smaxis  -  output, SGS-85 earth semi-major axis in meters
%           b_smaxis  -  output, SGS-85 earth semi-minor axis in meters
%           eccentr   -  output, SGS-85 earth eccentricity 
%           eccentr2  -  output, SGS-85 earth eccentricity squared
%           flatness  -  output, SGS-85 flatness (ellipticity)
%           gravpar   -  output, SGS-85 gravity parameter in meters**3/sec**2
%                        earth's gravitational constant (mass of earth
%                        including earth's atmosphere)
%           gravatm   -  output, SGS-85 gravitational constant of atmosphere
%                        in m**3/s**2
%           rot_rate  -  output, SGS-85 earth rotation rate in radians/second
%           c_speed   -  output, SGS-85 speed of light in vacuum in meters/ 
%                        second
%           g0        -  output, SGS-85 equatorial acceleration of gravity in 
%                        meters/sec**2
%           gcoratm   -  output, SGS-85 correction to the acceleration of 
%                        gravity at sea level because of atmosphere, in 
%                        meters/sec**2
%           j2        -  output, SGS-85 second zonal harmonic of the
%                        geopotential
%  Reference:
%           [1] Langley, R. B., GLONASS: Review and update. GPS World, vol. 8,
%               July 1997, pp. 46-51.
%  Last update: 10/15/97
%  Copyright (C) 1997 by LL Consulting. All Rights Reserved.

global  a_smaxis b_smaxis eccentr eccentr2 flatness gravpar gravatm rot_rate
global c_speed g0 gcoratm j2

%  Initialize the constants

a_smaxis = 6378136.; 
b_smaxis = 6356751.301568781;
eccentr  = 0.08181922145552;
eccentr2 = 0.00669438499959;     %  eccentr2 = flatness * (2. - flatness)
flatness = 0.00335281317790;     %  1. / 298.257 = 1 - b_smaxis/a_smaxis

gravpar  = 3.9860044e+14;
gravatm  = 0.35e+9;
rot_rate = 7.292115e-5; 
c_speed  = 2.99792458e+8;
g0       = 9.780328;
gcoratm  = - 0.9e-5;
j2       = -1082.63e-6;