/* -*- Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */ /* * Copyright (c) 1999 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the MASH Research * Group at the University of California Berkeley. * 4. Neither the name of the University nor of the Research Group may be * used to endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * Contributed by Tom Henderson, UCB Daedalus Research Group, June 1999 */ #ifndef lint static const char rcsid[] = "@(#) $Header: /nfs/jade/vint/CVSROOT/ns-2/satellite/satgeometry.cc,v 1.6 2001/05/21 19:27:31 haldar Exp $"; #endif #include "satgeometry.h" #include "satposition.h" static class SatGeometryClass : public TclClass { public: SatGeometryClass() : TclClass("SatGeometry") {} TclObject* create(int, const char*const*) { return (new SatGeometry()); } } class_sat_geometry; // Returns the distance in km between points a and b double SatGeometry::distance(coordinate a, coordinate b) { double a_x, a_y, a_z, b_x, b_y, b_z; // cartesian spherical_to_cartesian(a.r, a.theta, a.phi, a_x, a_y, a_z); spherical_to_cartesian(b.r, b.theta, b.phi, b_x, b_y, b_z); return (BaseTrace::round(DISTANCE(a_x, a_y, a_z, b_x, b_y, b_z), 1.0E+8)); } void SatGeometry::spherical_to_cartesian(double R, double Theta, double Phi, double &X, double &Y, double &Z) { X = R * sin(Theta) * cos (Phi); Y = R * sin(Theta) * sin (Phi); Z = R * cos(Theta); } // Propagation delay is the distance divided by the speed of light double SatGeometry::propdelay(coordinate a, coordinate b) { double delay = distance(a, b)/LIGHT; return (BaseTrace::round(delay, 1.0E+8)); } double SatGeometry::get_altitude(coordinate a) { return (a.r - EARTH_RADIUS); } // Returns latitude in radians, in the range from -PI/2 to PI/2 double SatGeometry::get_latitude(coordinate a) { return (PI/2 - a.theta); } // Returns (earth-centric) longitude corresponding to the position of the node // (the input coordinate corresponds to fixed coordinate system, through // which the Earth rotates, so we have to scale back the effects of rotation). // The return value ranges from -PI to PI. double SatGeometry::get_longitude(coordinate coord_) { double period = EARTH_PERIOD; // period of earth in seconds // adjust longitude so that it is earth-centric (i.e., account // for earth rotating beneath). double earth_longitude = fmod((coord_.phi - (fmod(NOW + SatPosition::time_advance_,period)/period) * 2*PI), 2*PI); // Bring earth_longitude to be within (-PI, PI) if (earth_longitude < (-1*PI)) earth_longitude = 2*PI + earth_longitude; if (earth_longitude > PI) earth_longitude = (-(2*PI - earth_longitude)); if (fabs(earth_longitude) < 0.0001) return 0; // To avoid trace output of "-0.00" else return (earth_longitude); } // If the satellite is above the elevation mask of the terminal, returns // the elevation mask in radians; otherwise, returns 0. double SatGeometry::check_elevation(coordinate satellite, coordinate terminal, double elev_mask_) { double S = satellite.r; // satellite radius double S_2 = satellite.r * satellite.r; // satellite radius^2 double E = EARTH_RADIUS; double E_2 = E * E; double d, theta, alpha; d = distance(satellite, terminal); if (d < sqrt(S_2 - E_2)) { // elevation angle > 0 theta = acos((E_2+S_2-(d*d))/(2*E*S)); alpha = acos(sin(theta) * S/d); return ( (alpha > elev_mask_) ? alpha : 0); } else return 0; } // This function determines whether two satellites are too far apart // to establish an ISL between them, due to Earth atmospheric grazing // (or shadowing by the Earth itself). Assumes that both satellites nodes // are at the same altitude. The line between the two satellites can be // bisected, and a perpendicular from that point to the Earth's center will // form a right triangle. If the length of this perpendicular is less than // EARTH_RADIUS + ATMOS_MARGIN, the link cannot be established. // int SatGeometry::are_satellites_mutually_visible(coordinate first, coordinate second) { // if we drop a perpendicular from the ISL to the Earth's surface, // we have a right triangle. The atmospheric margin is the minimum // ISL grazing altitude. double c, d, min_radius, grazing_radius; double radius = get_radius(first); // could just use first.r here. double distance_ = distance(first, second); c = radius * radius; d = (distance_/2) * (distance_/2); grazing_radius = (EARTH_RADIUS + ATMOS_MARGIN); min_radius = sqrt(c - d); if (min_radius >= grazing_radius) { return TRUE; } else { return FALSE; } }