?? cearth.cpp
字號:
void CEarth::m_ComputeFlattening( void )
{
if ( m_EquatorialRadiusInMeters == 0.0 || m_PolarRadiusInMeters == 0.0 )
{
return;
}
m_Flattening = CMath::AbsoluteValue( m_EquatorialRadiusInMeters - m_PolarRadiusInMeters ) / m_EquatorialRadiusInMeters;
//printf( "Flattening = %.23lf\n", m_Flattening );
}
void CEarth::m_Initialize( void )
{
m_EllipsoidID = 0;
m_PolarRadiusInMeters = 0.0;
m_EquatorialRadiusInMeters = 0.0;
m_Flattening = 0.0;
m_EccentricitySquared = 0.0;
}
void CEarth::SetEllipsoid( int ellipsoid_identifier )
{
m_EllipsoidID = ellipsoid_identifier;
switch( ellipsoid_identifier )
{
case Perfect_Sphere:
m_EquatorialRadiusInMeters = 6378137.0;
m_PolarRadiusInMeters = 6378137.0;
break;
case Airy:
m_EquatorialRadiusInMeters = 6377563.396;
m_PolarRadiusInMeters = 6356256.909237;
break;
case Austrailian_National:
m_EquatorialRadiusInMeters = 6378160.0;
m_PolarRadiusInMeters = 6356774.719195;
break;
case Bessell_1841:
m_EquatorialRadiusInMeters = 6377397.155;
m_PolarRadiusInMeters = 6356078.962818;
break;
case Bessel_1841_Nambia:
m_EquatorialRadiusInMeters = 6377483.865;
m_PolarRadiusInMeters = 6356165.382966;
break;
case Clarke_1866:
m_EquatorialRadiusInMeters = 6378206.4;
m_PolarRadiusInMeters = 6356583.799999;
break;
case Clarke_1880:
m_EquatorialRadiusInMeters = 6378249.145;
m_PolarRadiusInMeters = 6356514.86955;
break;
case Everest:
m_EquatorialRadiusInMeters = 6377276.345;
m_PolarRadiusInMeters = 6356075.41314;
break;
case Fischer_1960_Mercury:
m_EquatorialRadiusInMeters = 6378166.0;
m_PolarRadiusInMeters = 6356784.283607;
break;
case Fischer_1968:
m_EquatorialRadiusInMeters = 6378150.0;
m_PolarRadiusInMeters = 6356768.337244;
break;
case GRS_1967:
m_EquatorialRadiusInMeters = 6378160.0;
m_PolarRadiusInMeters = 6356774.516091;
break;
case GRS_1980:
m_EquatorialRadiusInMeters = 6378137.0;
m_PolarRadiusInMeters = 6356752.31414;
break;
case Helmert_1906:
m_EquatorialRadiusInMeters = 6378200.0;
m_PolarRadiusInMeters = 6356818.169628;
break;
case Hough:
m_EquatorialRadiusInMeters = 6378270.0;
m_PolarRadiusInMeters = 6356794.343434;
break;
case International:
m_EquatorialRadiusInMeters = 6378388.0;
m_PolarRadiusInMeters = 6356911.946128;
break;
case Krassovsky:
m_EquatorialRadiusInMeters = 6378245.0;
m_PolarRadiusInMeters = 6356863.018773;
break;
case Modified_Airy:
m_EquatorialRadiusInMeters = 6377340.189;
m_PolarRadiusInMeters = 6356034.447939;
break;
case Modified_Everest:
m_EquatorialRadiusInMeters = 6377304.063;
m_PolarRadiusInMeters = 6356103.038993;
break;
case Modified_Fischer_1960:
m_EquatorialRadiusInMeters = 6378155.0;
m_PolarRadiusInMeters = 6356773.320483;
break;
case South_American_1969:
m_EquatorialRadiusInMeters = 6378160.0;
m_PolarRadiusInMeters = 6356774.719195;
break;
case Topex_Poseidon_Pathfinder_ITRF: // Source is http://neptune.gsfc.nasa.gov/~krachlin/corr/refframe.html
m_EquatorialRadiusInMeters = 6378136.3;
m_PolarRadiusInMeters = 6356751.6005629376;
break;
case WGS_60:
m_EquatorialRadiusInMeters = 6378165.0;
m_PolarRadiusInMeters = 6356783.286959;
break;
case WGS_66:
m_EquatorialRadiusInMeters = 6378145.0;
m_PolarRadiusInMeters = 6356759.769489;
break;
case WGS_72:
m_EquatorialRadiusInMeters = 6378135.0;
m_PolarRadiusInMeters = 6356750.520016;
break;
case WGS_84:
// Computed polar radius from the flattening value specified at
// http://acro.harvard.edu/SSA/BGA/wg84figs.html
// because it had the most digits after the decimal point.
m_EquatorialRadiusInMeters = 6378137.0;
m_PolarRadiusInMeters = 6356752.3142451793;
break;
case Unknown:
default:
m_EllipsoidID = Unknown;
m_Initialize();
return;
}
m_ComputeFlattening();
m_ComputeEccentricitySquared();
}
void CEarth::SetEllipsoidByRadii( double equatorial_radius, double polar_radius )
{
m_EquatorialRadiusInMeters = equatorial_radius;
m_PolarRadiusInMeters = polar_radius;
m_EllipsoidID = Custom;
m_ComputeFlattening();
m_ComputeEccentricitySquared();
}
void CEarth::SetEllipsoidByEquatorialRadiusAndFlattening( double equatorial_radius, double flattening )
{
m_EquatorialRadiusInMeters = equatorial_radius;
m_Flattening = flattening;
m_EllipsoidID = Custom;
// We must compute the polar radius
double temp_double = m_Flattening * m_EquatorialRadiusInMeters;
m_PolarRadiusInMeters = m_EquatorialRadiusInMeters - temp_double;
m_ComputeEccentricitySquared();
}
#if 0
<WFC_DOCUMENTATION>
<HTML>
<HEAD><TITLE>GFC - CEarth</TITLE></HEAD>
<BODY>
<H1>CEarth</H1>
$Revision: 11 $
<HR>
<H2>Description</H2>
This class encapsulates the Earth. It holds the data necessary to perform the
calculations of distance and direction. The Earth is not a perfect sphere.
It is an ellipsoid (flattened at the top and bottom). All angles are expressed
in degrees and all distances are expressed in meters.
<H2>Methods</H2>
<DL COMPACT>
<DT><PRE>void <B>AddLineOfSightDistanceAndDirectionToCoordinate</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, double distance, double direction, <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2, double height_above_surface_of_point_2 = 0.0 )</PRE><DD>
If you were to shine a laser from <CODE>point_1</CODE> pointing towards <CODE>direction</CODE>
for <CODE>distance</CODE> meters, this function will tell you what location you would
be at. It will also let you specify a point <CODE>height_above_surface_of_point_2</CODE>
meters above the surface. This method does not take into account the curvature of
the Earth.
<DT><PRE>void <B>AddSurfaceDistanceAndDirectionToCoordinate</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1, double distance, double direction, <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_2 )
void <B>AddSurfaceDistanceAndDirectionToCoordinate</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1, double distance, double direction, <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2 )
void <B>AddSurfaceDistanceAndDirectionToCoordinate</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, double distance, double direction, <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_2 )
void <B>AddSurfaceDistanceAndDirectionToCoordinate</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, double distance, double direction, <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2 )</PRE><DD>
This allows you to add a distance over the surface of the Earth to a location and
get a new location. It answers the question "If I head out in this direction
for that amout of meters, where will I be?"
<DT><PRE>void <B>Convert</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& cartesian_coordinate, <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& polar_coordinate ) const
void <B>Convert</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& polar_coordinate, <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& cartesian_coordinate ) const</PRE><DD>
This method allows you to convert from polar and cartestian coordinates.
<DT><PRE>double <B>GetDistanceToHorizon</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1 ) const
double <B>GetDistanceToHorizon</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1 ) const</PRE><DD>
This tells you how far (in meters) from the horizon <CODE>point_1</CODE> is.
<DT><PRE>double <B>GetEquatorialRadiusInMeters</B>( void ) const</PRE><DD>
This tells you what the equatorial radius is in meters for the selected ellipsoid.
<DT><PRE>double <B>GetPolarRadiusInMeters</B>( void ) const</PRE><DD>
This tells you what the polar radius is in meters for the selected ellipsoid.
<DT><PRE>double <B>GetLineOfSightDistanceFromCourse</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& current_location, const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_a, const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_b ) const</PRE><DD>
Draw a line from <CODE>point_a</CODE> to <CODE>point_b</CODE>. This function will tell
you how far <CODE>current_location</CODE> is from that line.
<DT><PRE>double <B>GetLineOfSightDistance</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1, const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_2 ) const
double <B>GetLineOfSightDistance</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_2 ) const
double <B>GetLineOfSightDistance</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1, const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2 ) const
double <B>GetLineOfSightDistance</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2 ) const</PRE><DD>
This will tell you how many meters it is between two points. It answers the question, "If I
pointed a laser from <CODE>point_1</CODE> to <CODE>point_2</CODE>, how far would the
laser beam travel?"
<DT><PRE>double <B>GetSurfaceDistance</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1, const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_2, double * heading_from_point_1_to_point_2 = 0, double * heading_from_point_2_to_point_1 = 0 ) const
double <B>GetSurfaceDistance</B>( const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_1, const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2, double * heading_from_point_1_to_point_2 = 0, double * heading_from_point_2_to_point_1 = 0 ) const
double <B>GetSurfaceDistance</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, const <A HREF="CEarthCoordinate.htm">CEarthCoordinate</A>& point_2, double * heading_from_point_1_to_point_2 = 0, double * heading_from_point_2_to_point_1 = 0 ) const
double <B>GetSurfaceDistance</B>( const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_1, const <A HREF="CPolarCoordinate.htm">CPolarCoordinate</A>& point_2, double * heading_from_point_1_to_point_2 = 0, double * heading_from_point_2_to_point_1 = 0 ) const</PRE><DD>
This will tell you how many meters it is between two points. It answers the question, "If I
were to walk from <CODE>point_1</CODE> to <CODE>point_2</CODE>, how far would I walk?"
<DT><PRE>void <B>SetEllipsoid</B>( int ellipsoid )</PRE><DD>
This allows you to set the ellipsoid used by <B>CEarth</B> in its calculations. The
default is <CODE>WGS84</CODE> which is generally accepted as being the closest
approximation of the Earth's ellipsoid. The <CODE>ellipsoid</CODE> parameter
may be one of the following:
<UL>
<LI>Perfect_Sphere
<LI>Airy,
<LI>Austrailian_National,
<LI>Bessell_1841,
<LI>Bessel_1841_Nambia,
<LI>Clarke_1866,
<LI>Clarke_1880,
<LI>Everest,
<LI>Fischer_1960_Mercury,
<LI>Fischer_1968,
<LI>GRS_1967,
<LI>GRS_1980,
<LI>Helmert_1906,
<LI>Hough,
<LI>International,
<LI>Krassovsky,
<LI>Modified_Airy,
<LI>Modified_Everest,
<LI>Modified_Fischer_1960,
<LI>South_American_1969,
<LI>Topex_Poseidon_Pathfinder_ITRF,
<LI>WGS_60,
<LI>WGS_66,
<LI>WGS_72,
<LI>WGS_84
<LI>NAD_27
<LI>Tokyo
</UL>
<DT><PRE>void <B>SetEllipsoidByRadii</B>( double equatorial_radius, double polar_radius )</PRE><DD>
This let's you use your own (custom) values to describe the ellipsoid of the Earth.
<DT><PRE>void <B>SetEllipsoidByEquatorialRadiusAndFlattening</B>( double equatorial_radius, double flattening )</PRE><DD>
This let's you use your own (custom) values to describe the ellipsoid of the Earth.
</DL>
<H2>Example</H2>
<PRE><CODE>#include <stdio.h>
#include <GFC.h>
#pragma hdrstop
void main( void )
{
// Let's figure out how far it is from here to there
CPolarCoordinate here;
CPolarCoordinate there;
// Convert from Latitude/Longitude to coordinates our system understands
// here is 39 degrees 12.152 minutes North Latitude, 76 degrees 46.795 minutes West Longitude
here.SetUpDownAngleInDegrees( CMath::ConvertDegreesMinutesSecondsCoordinateToDecimalDegrees( 39.0, 12.152, 0.0 ) );
here.SetLeftRightAngleInDegrees( CMath::ConvertDegreesMinutesSecondsCoordinateToDecimalDegrees( -76.0, 46.795, 0.0 ) );
// there is 12 degrees 8.535 minutes North Latitude, 68 degrees 16.547 West Longitude
there.SetUpDownAngleInDegrees( CMath::ConvertDegreesMinutesSecondsCoordinateToDecimalDegrees( 12.0, 8.535, 0.0 ) );
there.SetLeftRightAngleInDegrees( CMath::ConvertDegreesMinutesSecondsCoordinateToDecimalDegrees( -68.0, 16.547, 0.0 ) );
<B>CEarth</B> earth; // We are talking about the earth...
double distance_in_meters = 0.0;
double heading_from_here_to_there = 0.0;
double heading_from_there_to_here = 0.0;
distance_in_meters = earth.GetSurfaceDistance( here, there, &heading_from_here_to_there, &heading_from_there_to_here );
printf( "Distance between here and there: %.23lf meters\nHeading from here to there: %.19lf degrees\nHeading from there to here: %.19lf degrees\n",
distance_in_meters,
heading_from_here_to_there,
heading_from_there_to_here );
double degrees = 0.0;
double minutes = 0.0;
double seconds = 0.0;
CMath::ConvertDecimalDegreesToDegreesMinutesSeconds( heading_from_here_to_there, degrees, minutes, seconds );
printf( "Heading %lf degrees, %lf minutes, %lf seconds\n", degrees, minutes, seconds );
CMath::ConvertDecimalDegreesToDegreesMinutesSeconds( heading_from_there_to_here, degrees, minutes, seconds );
printf( "Heading %lf degrees, %lf minutes, %lf seconds\n", degrees, minutes, seconds );
}</CODE></PRE>
<I>Copyright, 1998, Samuel R. Blackburn</I><BR>
$Workfile: CEarth.cpp $<BR>
$Modtime: 9/01/98 9:56p $
</BODY>
</HTML>
</WFC_DOCUMENTATION>
ToolTipFormatLine=CEarth=m_EllipsoidID=<m_EllipsoidID>
#endif
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