com.irurueta.navigation.geodesic.GeodesicLine

public class GeodesicLine extends Object

A geodesic line GeodesicLine facilitates the determination of a series of points on a single geodesic. The starting point (lat1, lon1) and the azimuth azi1 are specified in the constructor; alternatively, the Geodesic.line(double, double, double) method can be used to create a GeodesicLine. position(double) returns the location of point 2 a distance s12 along the geodesic. Alternatively arcPosition(double) gives the position of point 2 an arc length a12 along the geodesic. You can register the position of a reference point 3 a distance (arc length), s13 (a13) along the geodesic with the setDistance(double) (setArc(double)) functions. Points a fractional distance along the line can be found by providing, for example, 0.5 * getDistance() as an argument to position(double). The Geodesic.inverseLine(double, double, double, double) or Geodesic.directLine(double, double, double, double) methods return GeodesicLine objects with point 3 set to the point 2 of the corresponding geodesic problem. GeodesicLine objects created with the public constructor or with Geodesic.line(double, double, double) have s13 and a13 set to NaNs. The calculations are accurate to better than 15 nm (15 nanometers). See Sec. 9 of arXiv:1102.1215v1 for details. The algorithms used by this class are based on series expansions using the flattening f as a small parameter. These are only accurate for |f < 0.02; however reasonably accurate results will be obtained for |f < 0.2. The algorithms are described in

C. F. F. Karney, Algorithms for geodesics, J. Geodesy 87, 43–55 (2013) (addenda).

Here's an example of using this class

 
 import net.sf.geographiclib.*;
 public class GeodesicLineTest {
   public static void main(String[] args) {
     // Print waypoints between JFK and SIN
     Geodesic geod = Geodesic.WGS84;
     double
       lat1 = 40.640, lon1 = -73.779, // JFK
       lat2 =  1.359, lon2 = 103.989; // SIN
     GeodesicLine line = geod.InverseLine(lat1, lon1, lat2, lon2,
                                          GeodesicMask.DISTANCE_IN |
                                          GeodesicMask.LATITUDE |
                                          GeodesicMask.LONGITUDE);
     double ds0 = 500e3;     // Nominal distance between points = 500 km
     // The number of intervals
     int num = (int)(Math.ceil(line.Distance() / ds0));
     {
       // Use intervals of equal length
       double ds = line.Distance() / num;
       for (int i = 0; i <= num; ++i) {
         GeodesicData g = line.Position(i * ds,
                                        GeodesicMask.LATITUDE |
                                        GeodesicMask.LONGITUDE);
         System.out.println(i + " " + g.lat2 + " " + g.lon2);
       }
     }
     {
       // Slightly faster, use intervals of equal arc length
       double da = line.Arc() / num;
       for (int i = 0; i <= num; ++i) {
         GeodesicData g = line.ArcPosition(i * da,
                                           GeodesicMask.LATITUDE |
                                           GeodesicMask.LONGITUDE);
         System.out.println(i + " " + g.lat2 + " " + g.lon2);
       }
     }
   }
 }

Field Summary

Fields

Modifier and Type

Field

Description

private double

a

private double

a13

private double

a1m1

private double

a2m1

private double

a3c

private double

a4

private double

azi1

private double

b

private double

b11

private double

b21

private double

b31

private double

b41

private double[]

c1a

private double[]

c1pa

private double

c2

private double[]

c2a

private double[]

c3a

private double[]

c4a

private double

calp0

private double

calp1

private int

caps

private double

comg1

private double

csig1

private double

ctau1

private double

dn1

private double

f

private double

f1

private double

k2

private double

lat1

private double

lon1

private static final int

NC1

private static final int

NC1P

private static final int

NC2

private static final int

NC3

private static final int

NC4

private double

s13

private double

salp0

private double

salp1

private double

somg1

private double

ssig1

private double

stau1
Constructor Summary

Constructors

Modifier

Constructor

Description

GeodesicLine(Geodesic g, double lat1, double lon1, double azi1)

Constructor for a geodesic line staring at latitude lat1, longitude lon1, and azimuth azi1 (all in degrees).

protected

GeodesicLine(Geodesic g, double lat1, double lon1, double azi1, double salp1, double calp1, int caps, boolean arcmode, double s13A13)

GeodesicLine(Geodesic g, double lat1, double lon1, double azi1, int caps)

Constructor for a geodesic line starting at latitude lat1, longitude lon1, and azimuth azi1 (all in degrees) with a subset of the capabilities included.
Method Summary

Modifier and Type

Method

Description

GeodesicData

arcPosition(double a12)

Compute the position of point 2 which is an arc length a12 (degrees) from point 1.

GeodesicData

arcPosition(double a12, int outmask)

Compute the position of point 2 which is an arc length a12 (degrees) from point 1 and with a subset of th geodesic results returned.

boolean

capabilities(int testcaps)

Indicates whether this GeodesicLine object has all tested capabilities

double

genDistance(boolean arcmode)

The distance or arc length to point 3.

void

genSetDistance(boolean arcmode, double s13A13)

Specify position of point 3 in terms of either distance or arc length.

double

getArc()

Gets the arc length to point 3 (degrees).

double

getAzimuth()

Gets the azimuth (degrees) of the geodesic line at point 1.

Pair

getAzimuthCosines()

Gets a pair of sine and cosine of azi1 the azimuth (degrees) of the geodesic line at point 1.

int

getCapabilities()

Gets the computational capabilities that this object was constructed with.

double

getDistance()

Gets the distance to point 3 (meters).

double

getEquatorialArc()

Gets the arc length (degrees) between the northward equatorial crossing and point 1.

double

getEquatorialAzimuth()

Gets the azimuth (degrees) of the geodesic line as it crosses the equator in a northward direction.

Pair

getEquatorialAzimuthCosines()

Gets a pair of sine and cosine of azi0 the azimuth of the godesic line as it crosses the equator in a northward direction.

double

getFlattening()

Gets the flattening of the ellipsoid.

double

getLatitude()

Gets the latitude of point 1 (degrees).

double

getLongitude()

Gets the longitude of point 1 (degrees).

double

getMajorRadius()

Gets the equatorial radius of the ellipsoid (meters).

private boolean

init()

private void

lineInit(Geodesic g, double lat1, double lon1, double azi1, double salp1, double calp1, int caps)

GeodesicData

position(boolean arcmode, double s12A12, int outmask)

The general position function.

GeodesicData

position(double s12)

Compute the position of point 2 which is a distance s12 (meters) from point 1.

GeodesicData

position(double s12, int outmask)

Compute the position of point 2 which is a distance s12 (meters) from point 1 and with a subset of the geodesic results returned.

(package private) void

setArc(double a13)

Specify position of point 3 in terms of arc length.

void

setDistance(double s13)

Specify position of point 3 in terms of distance.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details
- NC1
  
  private static final int NC1
  See Also:
  
  Constant Field Values
- NC1P
  
  private static final int NC1P
  See Also:
  
  Constant Field Values
- NC2
  
  private static final int NC2
  See Also:
  
  Constant Field Values
- NC3
  
  private static final int NC3
  See Also:
  
  Constant Field Values
- NC4
  
  private static final int NC4
  See Also:
  
  Constant Field Values
- lat1
  
  private double lat1
- lon1
  
  private double lon1
- azi1
  
  private double azi1
- a
  
  private double a
- f
  
  private double f
- b
  
  private double b
- c2
  
  private double c2
- f1
  
  private double f1
- salp0
  
  private double salp0
- calp0
  
  private double calp0
- k2
  
  private double k2
- salp1
  
  private double salp1
- calp1
  
  private double calp1
- ssig1
  
  private double ssig1
- csig1
  
  private double csig1
- dn1
  
  private double dn1
- stau1
  
  private double stau1
- ctau1
  
  private double ctau1
- somg1
  
  private double somg1
- comg1
  
  private double comg1
- a1m1
  
  private double a1m1
- a2m1
  
  private double a2m1
- a3c
  
  private double a3c
- b11
  
  private double b11
- b21
  
  private double b21
- b31
  
  private double b31
- a4
  
  private double a4
- b41
  
  private double b41
- a13
  
  private double a13
- s13
  
  private double s13
- c1a
  
  private double[] c1a
- c1pa
  
  private double[] c1pa
- c2a
  
  private double[] c2a
- c3a
  
  private double[] c3a
- c4a
  
  private double[] c4a
- caps
  
  private int caps
Constructor Details
- GeodesicLine
  
  public GeodesicLine(Geodesic g, double lat1, double lon1, double azi1)
  
  Constructor for a geodesic line staring at latitude lat1, longitude lon1, and azimuth azi1 (all in degrees). If the point is at a pole, the azimuth is defined by keeping lon1 fixed, writing lat1 = ±(90° − ε), and taking the limit ε → 0+.
  
  Parameters:
  
  g - a Geodesic object used to compute the necessary information about the GeodesicLine
  
  lat1 - latitude of point 1 (degrees). lat1 should be in the range [−90°, 90°].
  
  lon1 - longitude of point 1 (degrees).
  
  azi1 - azimuth at point 1 (degrees).
- GeodesicLine
  
  public GeodesicLine(Geodesic g, double lat1, double lon1, double azi1, int caps)
  Constructor for a geodesic line starting at latitude lat1, longitude lon1, and azimuth azi1 (all in degrees) with a subset of the capabilities included. The GeodesicMask values are:
  
  caps |= GeodesicMask.LATITUDE for the latitude lat2; this is added automatically
  
  caps |= GeodesicMask.LONGITUDE for the longitude lon2
  
  caps |= GeodesicMask.AZIMUTH for the azimuth azi2; this is added automatically
  
  caps |= GeodesicMask.DISTANCE for the distance s12
  
  caps |= GeodesicMask.REDUCED_LENGTH for the reduced length m12
  
  caps |= GeodesicMask.GEODESIC_SCALE for the geodesic scales M12 and M21
  
  caps |= GeodesicMask.AREA for the area S12
  
  caps |= GeodesicMask.DISTANCE_IN permits the length of the geodesic to be given in terms of s12; without this capability the length can only be specified in terms of arc length
  
  caps |= GeodesicMask.ALL for all of the above.
  Parameters:
  
  g - a Geodesic object used to compute the necessary information about the GeodesicLine.
  
  lat1 - latitude of point 1 (degrees).
  
  lon1 - longitude of point 1 (degrees).
  
  azi1 - azimuth at point 1 (degrees).
  
  caps - bitor'ed combination of GeodesicMask values specifying the capabilities the GeodesicLine object should possess, i.e., which quantities can be returned in calls to position(double).
- GeodesicLine
  
  protected GeodesicLine(Geodesic g, double lat1, double lon1, double azi1, double salp1, double calp1, int caps, boolean arcmode, double s13A13)
Method Details
- position
  
  public GeodesicData position(double s12)
  
  Compute the position of point 2 which is a distance s12 (meters) from point 1. The values of lon2 and azi2 returned are in the range [−180°, 180°]. The GeodesicLine object must have been constructed with caps |= GeodesicMask.DISTANCE_IN; otherwise no parameters are set.
  
  Parameters:
  
  s12 - distance from point 1 to point 2 (meters); it can be negative.
  
  Returns:
  
  a GeodesicData object with the following fields: lat1, lon1, azi1, lat2, lon2, azi2, s12, a12. Some of these results may be missing if the GeodesicLine did not include the relevant capability.
- position
  
  public GeodesicData position(double s12, int outmask)
  
  Compute the position of point 2 which is a distance s12 (meters) from point 1 and with a subset of the geodesic results returned. The GeodesicLine object must have been constructed with caps |= GeodesicMask.DISTANCE_IN; otherwise no parameters are set. Requesting a value which the GeodesicLine object is not capable of computing is not an error (no parameters will be set). The value of lon2 returned is normally in the range [−180°, 180°]; however if the outmask includes the GeodesicMask.LONG_UNROLL flag, the longitude is "unrolled" so that the quantity lon2 − lon1 indicates how many times and in what sense the geodesic encircles the ellipsoid.
  
  Parameters:
  
  s12 - distance from point 1 to point 2 (meters); it can be negative.
  
  outmask - a bitor'ed combination of GeodesicMask values specifying which results should be returned.
  
  Returns:
  
  a GeodesicData object including the requested results.
- arcPosition
  
  public GeodesicData arcPosition(double a12)
  
  Compute the position of point 2 which is an arc length a12 (degrees) from point 1. The values of lon2 and azi2 returned are in the range [−180°, 180°]. The GeodesicLine object must have been constructed with caps |= GeodesicMask.DISTANCE_IN; otherwise no parameters are set.
  
  Parameters:
  
  a12 - arc length from point 1 to point 2 (degrees); it can be negative.
  
  Returns:
  
  a GeodesicData object with the following fields: lat1, lon1, azi1, lat2, lon2, azi2, s12, a12. Some of these results may be missing if the GeodesicLine did not include the relevant capability.
- arcPosition
  
  public GeodesicData arcPosition(double a12, int outmask)
  
  Compute the position of point 2 which is an arc length a12 (degrees) from point 1 and with a subset of th geodesic results returned. Requesting a value which the GeodesicLine object is not capable of computing is not an error (no parameters will be set). The value of lon2 returned is in the range [−180°, 180°], unless the outmask includes the GeodesicMask.LONG_UNROLL flags.
  
  Parameters:
  
  a12 - arc length from point 1 to point 2 (degrees); it can be negative.
  
  outmask - a bitor'ed combination of GeodesicMask values specifying which results should be returned.
  
  Returns:
  
  a GeodesicData object giving lat1, lon2, azi2, and a12.
- position
  
  public GeodesicData position(boolean arcmode, double s12A12, int outmask)
  The general position function. position(double, int) and arcPosition(double, int) are defined in terms of this function. The GeodesicMask values possible for outmask are
  
  outmask |= GeodesicMask.LATITUDE for the latitude lat2;
  
  outmask |= GeodesicMask.LONGITUDE for the latitude lon2;
  
  outmask |= GeodesicMask.AZIMUTH for the latitude azi2;
  
  outmask |= GeodesicMask.DISTANCE for the distance s12;
  
  outmask |= GeodesicMask.REDUCED_LENGTH for the reduced length m12;
  
  outmask |= GeodesicMask.GEODESIC_SCALE for the geodesic scales M12 and M21;
  
  outmask |= GeodesicMask.ALL for all of the above;
  
  outmask |= GeodesicMask.LONG_UNROLL to unroll lon2 (instead of reducing it to the range [−180°, 180°]).
  Parameters:
  
  arcmode - boolean flag determining the meaning of the second parameter; if arcmode is false, then the GeodesicLine object must have been constructed with caps |= GeodesicMask.DISTANCE_IN.
  
  s12A12 - if arcmode is false, this is the distance between point 1 and point 2 (meters); otherwise it is the arc length between point 1 and point 2 (degrees); it can be negative.
  
  outmask - a bitor'ed combination of GeodesicMask values specifying which results should be returned.
  
  Returns:
  
  a GeodesicData object with the requested results. Requesting a value which the GeodesicLine object is not capable of computing is not an error; Double.NaN is returned instead.
- setDistance
  
  public void setDistance(double s13)
  
  Specify position of point 3 in terms of distance. This is only useful if the GeodesicLine object has been constructed with caps |= GeodesicMask.DISTANCE_IN.
  
  Parameters:
  
  s13 - the distance from point 1 to point 3 (meters); it can be negative.
- genSetDistance
  
  public void genSetDistance(boolean arcmode, double s13A13)
  
  Specify position of point 3 in terms of either distance or arc length.
  
  Parameters:
  
  arcmode - boolean flag determining the meaning of the second parameter; if arcmode is false, then the GeodesicLine object must have been constructed with caps |= GeodesicMask.DISTANCE_IN.
  
  s13A13 - if arcmode is false, this is the distance from point 1 to point 3 (meters); otherwise it is the arc length from point 1 to point 3 (degrees); it can be negative.
- getLatitude
  
  public double getLatitude()
  
  Gets the latitude of point 1 (degrees).
  
  Returns:
  
  lat1 the latitude of point 1 (degrees).
- getLongitude
  
  public double getLongitude()
  
  Gets the longitude of point 1 (degrees).
  
  Returns:
  
  lon1 the longitude of point 1 (degrees).
- getAzimuth
  
  public double getAzimuth()
  
  Gets the azimuth (degrees) of the geodesic line at point 1.
  
  Returns:
  
  azi1 the azimuth (degrees) of the geodesic line at point 1.
- getAzimuthCosines
  
  public Pair getAzimuthCosines()
  
  Gets a pair of sine and cosine of azi1 the azimuth (degrees) of the geodesic line at point 1.
  
  Returns:
  
  pair of sine and cosine of azi1 the azimuth (degrees) of the geodesic line at point 1.
- getEquatorialAzimuth
  
  public double getEquatorialAzimuth()
  
  Gets the azimuth (degrees) of the geodesic line as it crosses the equator in a northward direction.
  
  Returns:
  
  azi0 the azimuth (degrees) of the geodesic line as it crosses the equator in a northward direction.
- getEquatorialAzimuthCosines
  
  public Pair getEquatorialAzimuthCosines()
  
  Gets a pair of sine and cosine of azi0 the azimuth of the godesic line as it crosses the equator in a northward direction.
  
  Returns:
  
  pair of sine and cosine of azi0 the azimuth of the godesic line as it crosses the equator in a northward direction.
- getEquatorialArc
  
  public double getEquatorialArc()
  
  Gets the arc length (degrees) between the northward equatorial crossing and point 1.
  
  Returns:
  
  a1 the arc length (degrees) between the northward equatorial crossing and point 1.
- getMajorRadius
  
  public double getMajorRadius()
  
  Gets the equatorial radius of the ellipsoid (meters). This is the value inherited from the Geodesic object used in the constructor.
  
  Returns:
  
  a the equatorial radius of the ellipsoid (meters).
- getFlattening
  
  public double getFlattening()
  
  Gets the flattening of the ellipsoid. This is the value inherited from the Geodesic object used in the constructor.
  
  Returns:
  
  f the flattening of the ellipsoid.
- getCapabilities
  
  public int getCapabilities()
  
  Gets the computational capabilities that this object was constructed with. LATITUDE and AZIMUTH are always included.
  
  Returns:
  
  caps the computation capabilities that this object was constructed with.
- capabilities
  
  public boolean capabilities(int testcaps)
  
  Indicates whether this GeodesicLine object has all tested capabilities
  
  Parameters:
  
  testcaps - a set of bitor'ed GeodesicMask values.
  
  Returns:
  
  true if the GeodesicLine object has all these capabilities.
- genDistance
  
  public double genDistance(boolean arcmode)
  
  The distance or arc length to point 3.
  
  Parameters:
  
  arcmode - boolean flag determining the meaning of returned value.
  
  Returns:
  
  s13 if arcmode is false; a13 if arcmode is true.
- getDistance
  
  public double getDistance()
  
  Gets the distance to point 3 (meters).
  
  Returns:
  
  s13 the disance to point 3 (meters).
- getArc
  
  public double getArc()
  
  Gets the arc length to point 3 (degrees).
  
  Returns:
  
  a13 the arc length to point 3 (degrees).
- setArc
  
  void setArc(double a13)
  
  Specify position of point 3 in terms of arc length. The distance s13 is only set if the GeodesicLine object has been constructed with caps |= GeodesicMask.DISTANCE.
  
  Parameters:
  
  a13 - the arc length from point 1 to point 3 (degrees); it can be negative.
- init
  
  private boolean init()
  
  Returns:
  
  true if the object has been initialized.
- lineInit
  
  private void lineInit(Geodesic g, double lat1, double lon1, double azi1, double salp1, double calp1, int caps)

Class GeodesicLine

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Details

NC1

NC1P

NC2

NC3

NC4

lat1

lon1

azi1

a

f

b

c2

f1

salp0

calp0

k2

salp1

calp1

ssig1

csig1

dn1

stau1

ctau1

somg1

comg1

a1m1

a2m1

a3c

b11

b21

b31

a4

b41

a13

s13

c1a

c1pa

c2a

c3a

c4a

caps

Constructor Details

GeodesicLine

GeodesicLine

GeodesicLine

Method Details

position

position

arcPosition

arcPosition

position

setDistance

genSetDistance

getLatitude

getLongitude

getAzimuth

getAzimuthCosines

getEquatorialAzimuth

getEquatorialAzimuthCosines

getEquatorialArc

getMajorRadius

getFlattening

getCapabilities

capabilities

genDistance

getDistance

getArc

setArc

init

lineInit