package uk.me.jstott.jcoord;
/**
* Class to represent an Ordnance Survey grid reference
*
* (c) 2006 Jonathan Stott
*
* Created on 11-02-2006
*
* @author Jonathan Stott
* @version 1.0
* @since 1.0
*/
public class OSRef {
/**
* Easting
*/
private double easting;
/**
* Northing
*/
private double northing;
/**
* Create a new Ordnance Survey grid reference.
*
* @param easting
* the easting in metres
* @param northing
* the northing in metres
* @since 1.0
*/
public OSRef(double easting, double northing) {
this.easting = easting;
this.northing = northing;
}
/**
* Take a string formatted as a six-figure OS grid reference (e.g. "TG514131")
* and create a new OSRef object that represents that grid reference. The
* first character must be H, N, S, O or T. The second character can be any
* uppercase character from A through Z excluding I.
*
* @param ref
* a String representing a six-figure Ordnance Survey grid reference
* in the form XY123456
* @throws IllegalArgumentException
* if ref is not of the form XY123456
* @since 1.0
*/
public OSRef(String ref) throws IllegalArgumentException {
// if (ref.matches(""))
char char1 = ref.charAt(0);
char char2 = ref.charAt(1);
// Thanks to Nick Holloway for pointing out the radix bug here
int east = Integer.parseInt(ref.substring(2, 5)) * 100;
int north = Integer.parseInt(ref.substring(5, 8)) * 100;
if (char1 == 'H') {
north += 1000000;
} else if (char1 == 'N') {
north += 500000;
} else if (char1 == 'O') {
north += 500000;
east += 500000;
} else if (char1 == 'T') {
east += 500000;
}
int char2ord = char2;
if (char2ord > 73)
char2ord--; // Adjust for no I
double nx = ((char2ord - 65) % 5) * 100000;
double ny = (4 - Math.floor((char2ord - 65) / 5)) * 100000;
easting = east + nx;
northing = north + ny;
}
/**
* Return a String representation of this OSGB grid reference showing the
* easting and northing.
*
* @return a String represenation of this OSGB grid reference
* @since 1.0
*/
public String toString() {
return "(" + easting + ", " + northing + ")";
}
/**
* Return a String representation of this OSGB grid reference using the
* six-figure notation in the form XY123456
*
* @return a String representing this OSGB grid reference in six-figure
* notation
* @since 1.0
*/
public String toSixFigureString() {
int hundredkmE = (int) Math.floor(easting / 100000);
int hundredkmN = (int) Math.floor(northing / 100000);
String firstLetter;
if (hundredkmN < 5) {
if (hundredkmE < 5) {
firstLetter = "S";
} else {
firstLetter = "T";
}
} else if (hundredkmN < 10) {
if (hundredkmE < 5) {
firstLetter = "N";
} else {
firstLetter = "O";
}
} else {
firstLetter = "H";
}
int index = 65 + ((4 - (hundredkmN % 5)) * 5) + (hundredkmE % 5);
// int ti = index;
if (index >= 73)
index++;
String secondLetter = Character.toString((char) index);
int e = (int) Math.floor((easting - (100000 * hundredkmE)) / 100);
int n = (int) Math.floor((northing - (100000 * hundredkmN)) / 100);
String es = "" + e;
if (e < 100)
es = "0" + es;
if (e < 10)
es = "0" + es;
String ns = "" + n;
if (n < 100)
ns = "0" + ns;
if (n < 10)
ns = "0" + ns;
return firstLetter + secondLetter + es + ns;
}
/**
* Convert this OSGB grid reference to a latitude/longitude pair using the
* OSGB36 datum. Note that, the LatLng object may need to be converted to the
* WGS84 datum depending on the application.
*
* @return a LatLng object representing this OSGB grid reference using the
* OSGB36 datum
* @since 1.0
*/
public LatLng toLatLng() {
double OSGB_F0 = 0.9996012717;
double N0 = -100000.0;
double E0 = 400000.0;
double phi0 = Math.toRadians(49.0);
double lambda0 = Math.toRadians(-2.0);
double a = RefEll.AIRY_1830.getMaj();
double b = RefEll.AIRY_1830.getMin();
double eSquared = RefEll.AIRY_1830.getEcc();
double phi = 0.0;
double lambda = 0.0;
double E = this.easting;
double N = this.northing;
double n = (a - b) / (a + b);
double M = 0.0;
double phiPrime = ((N - N0) / (a * OSGB_F0)) + phi0;
do {
M =
(b * OSGB_F0)
* (((1 + n + ((5.0 / 4.0) * n * n) + ((5.0 / 4.0) * n * n * n)) * (phiPrime - phi0))
- (((3 * n) + (3 * n * n) + ((21.0 / 8.0) * n * n * n))
* Math.sin(phiPrime - phi0) * Math.cos(phiPrime + phi0))
+ ((((15.0 / 8.0) * n * n) + ((15.0 / 8.0) * n * n * n))
* Math.sin(2.0 * (phiPrime - phi0)) * Math
.cos(2.0 * (phiPrime + phi0))) - (((35.0 / 24.0) * n * n * n)
* Math.sin(3.0 * (phiPrime - phi0)) * Math
.cos(3.0 * (phiPrime + phi0))));
phiPrime += (N - N0 - M) / (a * OSGB_F0);
} while ((N - N0 - M) >= 0.001);
double v =
a * OSGB_F0
* Math.pow(1.0 - eSquared * Util.sinSquared(phiPrime), -0.5);
double rho =
a * OSGB_F0 * (1.0 - eSquared)
* Math.pow(1.0 - eSquared * Util.sinSquared(phiPrime), -1.5);
double etaSquared = (v / rho) - 1.0;
double VII = Math.tan(phiPrime) / (2 * rho * v);
double VIII =
(Math.tan(phiPrime) / (24.0 * rho * Math.pow(v, 3.0)))
* (5.0 + (3.0 * Util.tanSquared(phiPrime)) + etaSquared - (9.0 * Util
.tanSquared(phiPrime) * etaSquared));
double IX =
(Math.tan(phiPrime) / (720.0 * rho * Math.pow(v, 5.0)))
* (61.0 + (90.0 * Util.tanSquared(phiPrime)) + (45.0 * Util
.tanSquared(phiPrime) * Util.tanSquared(phiPrime)));
double X = Util.sec(phiPrime) / v;
double XI =
(Util.sec(phiPrime) / (6.0 * v * v * v))
* ((v / rho) + (2 * Util.tanSquared(phiPrime)));
double XII =
(Util.sec(phiPrime) / (120.0 * Math.pow(v, 5.0)))
* (5.0 + (28.0 * Util.tanSquared(phiPrime)) + (24.0 * Util
.tanSquared(phiPrime) * Util.tanSquared(phiPrime)));
double XIIA =
(Util.sec(phiPrime) / (5040.0 * Math.pow(v, 7.0)))
* (61.0
+ (662.0 * Util.tanSquared(phiPrime))
+ (1320.0 * Util.tanSquared(phiPrime) * Util
.tanSquared(phiPrime)) + (720.0 * Util.tanSquared(phiPrime)
* Util.tanSquared(phiPrime) * Util.tanSquared(phiPrime)));
phi =
phiPrime - (VII * Math.pow(E - E0, 2.0))
+ (VIII * Math.pow(E - E0, 4.0)) - (IX * Math.pow(E - E0, 6.0));
lambda =
lambda0 + (X * (E - E0)) - (XI * Math.pow(E - E0, 3.0))
+ (XII * Math.pow(E - E0, 5.0)) - (XIIA * Math.pow(E - E0, 7.0));
return new LatLng(Math.toDegrees(phi), Math.toDegrees(lambda));
}
/**
* Get the easting.
*
* @return the easting in metres
* @since 1.0
*/
public double getEasting() {
return easting;
}
/**
* Get the northing.
*
* @return the northing in metres
* @since 1.0
*/
public double getNorthing() {
return northing;
}
}