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//
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// cSite.cpp
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//
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// Copyright (c) 2003 Michael F. Henry
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//
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//////////////////////////////////////////////////////////////////////////////
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#include "stdafx.h"
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#include "cSite.h"
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#include "globals.h"
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//////////////////////////////////////////////////////////////////////////////
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// Construction/Destruction
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cSite::cSite(const cCoordGeo &geo) : m_geo(geo)
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{}
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//////////////////////////////////////////////////////////////////////////////
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// c'tor accepting:
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// Latitude in degress (negative south)
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// Longitude in degress (negative west)
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// Altitude in km
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cSite::cSite(double degLat, double degLon, double kmAlt) :
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m_geo(deg2rad(degLat), deg2rad(degLon), kmAlt)
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{}
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cSite::~cSite()
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{}
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//////////////////////////////////////////////////////////////////////////////
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// setGeo()
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// Set a new geographic position
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void cSite::setGeo(const cCoordGeo &geo)
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{
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m_geo = geo;
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}
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//////////////////////////////////////////////////////////////////////////////
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// getPosition()
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// Return the ECI coordinate of the site at the given time.
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cEci cSite::getPosition(const cJulian &date) const
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{
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return cEci(m_geo, date);
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}
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//////////////////////////////////////////////////////////////////////////////
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// getLookAngle()
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// Return the topocentric (azimuth, elevation, etc.) coordinates for a target
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// object described by the input ECI coordinates.
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cCoordTopo cSite::getLookAngle(const cEci &eci) const
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{
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// Calculate the ECI coordinates for this cSite object at the time
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// of interest.
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cJulian date = eci.getDate();
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cEci eciSite(m_geo, date);
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// The Site ECI units are km-based; ensure target ECI units are same
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assert(eci.UnitsAreKm());
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cVector vecRgRate(eci.getVel().m_x - eciSite.getVel().m_x,
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eci.getVel().m_y - eciSite.getVel().m_y,
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eci.getVel().m_z - eciSite.getVel().m_z);
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double x = eci.getPos().m_x - eciSite.getPos().m_x;
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double y = eci.getPos().m_y - eciSite.getPos().m_y;
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double z = eci.getPos().m_z - eciSite.getPos().m_z;
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double w = sqrt(sqr(x) + sqr(y) + sqr(z));
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cVector vecRange(x, y, z, w);
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// The site's Local Mean Sidereal Time at the time of interest.
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double theta = date.toLMST(getLon());
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double sin_lat = sin(getLat());
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double cos_lat = cos(getLat());
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double sin_theta = sin(theta);
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double cos_theta = cos(theta);
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double top_s = sin_lat * cos_theta * vecRange.m_x +
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sin_lat * sin_theta * vecRange.m_y -
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cos_lat * vecRange.m_z;
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double top_e = -sin_theta * vecRange.m_x +
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cos_theta * vecRange.m_y;
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double top_z = cos_lat * cos_theta * vecRange.m_x +
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cos_lat * sin_theta * vecRange.m_y +
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sin_lat * vecRange.m_z;
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double az = atan(-top_e / top_s);
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if (top_s > 0.0)
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az += PI;
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if (az < 0.0)
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az += 2.0*PI;
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double el = asin(top_z / vecRange.m_w);
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double rate = (vecRange.m_x * vecRgRate.m_x +
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vecRange.m_y * vecRgRate.m_y +
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vecRange.m_z * vecRgRate.m_z) / vecRange.m_w;
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cCoordTopo topo(az, // azimuth, radians
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el, // elevation, radians
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vecRange.m_w, // range, km
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rate); // rate, km / sec
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#ifdef WANT_ATMOSPHERIC_CORRECTION
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// Elevation correction for atmospheric refraction.
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// Reference: Astronomical Algorithms by Jean Meeus, pp. 101-104
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// Note: Correction is meaningless when apparent elevation is below horizon
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topo.m_El += deg2rad((1.02 /
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tan(deg2rad(rad2deg(el) + 10.3 /
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(rad2deg(el) + 5.11)))) / 60.0);
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if (topo.m_El < 0.0)
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topo.m_El = el; // Reset to true elevation
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if (topo.m_El > (PI / 2))
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topo.m_El = (PI / 2);
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#endif
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return topo;
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}
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//////////////////////////////////////////////////////////////////////////////
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// toString()
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//
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string cSite::toString() const
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{
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const int TEMP_SIZE = 128;
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char sz[TEMP_SIZE];
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bool LatNorth = true;
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bool LonEast = true;
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if (m_geo.m_Lat < 0.0)
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{
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LatNorth = false;
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}
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if (m_geo.m_Lon < 0.0)
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{
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LonEast = false;
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}
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snprintf(sz, TEMP_SIZE,
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"%06.3f%c, ",
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fabs(rad2deg(m_geo.m_Lat)),
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(LatNorth ? 'N' : 'S'));
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string strLoc = sz;
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snprintf(sz, TEMP_SIZE,
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"%07.3f%c, ",
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fabs(rad2deg(m_geo.m_Lon)),
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(LonEast ? 'E' : 'W'));
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strLoc += sz;
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snprintf(sz, TEMP_SIZE,
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"%.1fm\n",
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(m_geo.m_Alt * 1000.0));
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strLoc += sz;
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return strLoc;
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}
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