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Better distance computation (revisited)

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Arndt Brenschede 2018-12-07 00:45:12 +01:00
parent e7afb236a6
commit ab2f5e3ae0
12 changed files with 101 additions and 543 deletions
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90
brouter-util/src/main/java/btools/util/CheapRulerSingleton.java
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@ -12,69 +12,49 @@ public final class CheapRulerSingleton {
* This is implemented as a Singleton to have a unique cache for the cosine
* values across all the code.
*/
private static volatile CheapRulerSingleton instance = null;
// Conversion constants
public final static double ILATLNG_TO_LATLNG = 1e-6; // From integer to degrees
public final static int KILOMETERS_TO_METERS = 1000;
public final static double DEG_TO_RAD = Math.PI / 180.;
// Cosine cache constants
private final static int COS_CACHE_LENGTH = 8192;
private final static double COS_CACHE_MAX_DEGREES = 90.0;
private final static int SCALE_CACHE_LENGTH = 1800;
private final static int SCALE_CACHE_INCREMENT = 100000;
// COS_CACHE_LENGTH cached values between 0 and COS_CACHE_MAX_DEGREES degrees.
double[] COS_CACHE = new double[COS_CACHE_LENGTH];
private final static double[][] SCALE_CACHE = new double[SCALE_CACHE_LENGTH][];
/**
* Helper to build the cache of cosine values.
* build the cache of cosine values.
*/
private void buildCosCache() {
double increment = DEG_TO_RAD * COS_CACHE_MAX_DEGREES / COS_CACHE_LENGTH;
for (int i = 0; i < COS_CACHE_LENGTH; i++) {
COS_CACHE[i] = Math.cos(i * increment);
static {
for (int i = 0; i < SCALE_CACHE_LENGTH; i++) {
SCALE_CACHE[i] = calcKxKyFromILat( i*SCALE_CACHE_INCREMENT + SCALE_CACHE_INCREMENT/2 );
}
}
private CheapRulerSingleton() {
super();
// Build the cache of cosine values.
buildCosCache();
private static double[] calcKxKyFromILat(int ilat) {
double lat = DEG_TO_RAD*(ilat-90000000)/1000000.;
double cos = Math.cos(lat);
double cos2 = 2 * cos * cos - 1;
double cos3 = 2 * cos * cos2 - cos;
double cos4 = 2 * cos * cos3 - cos2;
double cos5 = 2 * cos * cos4 - cos3;
// Multipliers for converting integer longitude and latitude into distance
// (http://1.usa.gov/1Wb1bv7)
double[] kxky = new double[2];
kxky[0] = (111.41513 * cos - 0.09455 * cos3 + 0.00012 * cos5) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
kxky[1] = (111.13209 - 0.56605 * cos2 + 0.0012 * cos4) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
return kxky;
}
/**
* Get an instance of this singleton class.
* Calculate the degree->meter scale for given latitude
*
* @result [lon->meter,lat->meter]
*/
public final static CheapRulerSingleton getInstance() {
if (CheapRulerSingleton.instance == null) {
synchronized(CheapRulerSingleton.class) {
if (CheapRulerSingleton.instance == null) {
CheapRulerSingleton.instance = new CheapRulerSingleton();
}
}
}
return CheapRulerSingleton.instance;
}
/**
* Helper to compute the cosine of an integer latitude.
*/
public double cosIlat(int ilat) {
double latDegrees = ilat * ILATLNG_TO_LATLNG;
if (ilat > 90000000) {
// Use the symmetry of the cosine.
latDegrees -= 90;
}
return COS_CACHE[(int) (latDegrees * COS_CACHE_LENGTH / COS_CACHE_MAX_DEGREES)];
}
/**
* Helper to compute the cosine of a latitude (in degrees).
*/
public double cosLat(double lat) {
if (lat < 0) {
lat += 90.;
}
return COS_CACHE[(int) (lat * COS_CACHE_LENGTH / COS_CACHE_MAX_DEGREES)];
public static double[] getLonLatToMeterScales( int ilat ) {
return SCALE_CACHE[ ilat / SCALE_CACHE_INCREMENT ];
}
/**
@ -89,20 +69,10 @@ public final class CheapRulerSingleton {
* @note Integer longitude is ((longitude in degrees) + 180) * 1e6.
* Integer latitude is ((latitude in degrees) + 90) * 1e6.
*/
public double distance(int ilon1, int ilat1, int ilon2, int ilat2) {
double cos = cosIlat(ilat1);
double cos2 = 2 * cos * cos - 1;
double cos3 = 2 * cos * cos2 - cos;
double cos4 = 2 * cos * cos3 - cos2;
double cos5 = 2 * cos * cos4 - cos3;
// Multipliers for converting integer longitude and latitude into distance
// (http://1.usa.gov/1Wb1bv7)
double kx = (111.41513 * cos - 0.09455 * cos3 + 0.00012 * cos5) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
double ky = (111.13209 - 0.56605 * cos2 + 0.0012 * cos4) * ILATLNG_TO_LATLNG * KILOMETERS_TO_METERS;
double dlat = (ilat1 - ilat2) * ky;
double dlon = (ilon1 - ilon2) * kx;
public static double distance(int ilon1, int ilat1, int ilon2, int ilat2) {
double[] kxky = getLonLatToMeterScales( ( ilat1 + ilat2 ) >> 1 );
double dlon = (ilon1 - ilon2) * kxky[0];
double dlat = (ilat1 - ilat2) * kxky[1];
return Math.sqrt(dlat * dlat + dlon * dlon); // in m
}
}