I want to generate some randoms polygon but I want it to be more or less centered in the middle of the given window coordinates.
Here is my code, it generates a random polygon but most of the time it's on the bottom of the window and I'd like to have it a bit more centered:
private static final double CORNER_MARGIN = 100.0; // max offset for a corner of the field, to randomize the polygon
private static double[] standardPolygon(double x1, double x2, double y1, double y2) {
// minX maxX minY maxY --> it's the coordinate of the window
double centerX = (x1 + x2) / 2;
double centerY = (y1 + y2) / 2;
// this is a standard polygon "centered" in the middle of the program window
return new double[]{
x1 - (x2 - x1) * RANDOM.nextDouble(), y2 + (y2 - y1) *RANDOM.nextDouble() * CORNER_MARGIN,
x2 + (x2 - x1) * RANDOM.nextDouble(), y2 + (y2 - y1) *RANDOM.nextDouble() * CORNER_MARGIN,
x2 + (x2 - x1) * RANDOM.nextDouble(), y1 - (y2 - y1) *RANDOM.nextDouble() * CORNER_MARGIN,
x1 - (x2 - x1) * RANDOM.nextDouble(), y1 - (y2 - y1) *RANDOM.nextDouble() * CORNER_MARGIN,
};
/*return new double[]{
x1 - RANDOM.nextDouble() * CORNER_MARGIN, y2 + RANDOM.nextDouble() * CORNER_MARGIN, // up left
x2 + RANDOM.nextDouble() * CORNER_MARGIN, y2 + RANDOM.nextDouble() * CORNER_MARGIN, // up right
x2 + RANDOM.nextDouble() * CORNER_MARGIN, y1 - RANDOM.nextDouble() * CORNER_MARGIN, // down right
x1 - RANDOM.nextDouble() * CORNER_MARGIN, y1 - RANDOM.nextDouble() * CORNER_MARGIN, // down left
};*/
}
The code in comment is working but now I tried to center it but I only get some rectangles/squares. How can I manage to keep random polygon forms but a bit more centered ?
[EDIT]
Here is how I draw the area of the polygon :
private void drawZone(Group group, IGameParameters gameParameters) {
Polygon polygon = new Polygon();
double[] points = gameParameters.dronePadDeliveryZonePolygon();
List<Double> pointsList = new ArrayList<>();
for (double point : points) pointsList.add(point);
polygon.getPoints().addAll(pointsList);
polygon.setFill(Color.ANTIQUEWHITE);
group.getChildren().add(polygon);
}```
You calculated the center but don't use it anywhere. Just so I understand correctly, this is a 4-sided polygon only and the corners randomly positioned at most 100 from the corner of the window?
I'm not 100% sure on how you want the polygon to be shaped but give this a try. Logically it works in my head, but I don't have a way to test the code right now.
private static final double CORNER_MARGIN = 100.0;
private static double[] standardPolygon(double x1, double x2, double y1, double y2) {
double centerX = (x1 + x2) / 2;
double centerY = (y1 + y2) / 2;
// Get the corner offsets
ox1 = x1 + CORNER_MARGIN * RANDOM.nextDouble(); // top left
oy1 = y1 + CORNER_MARGIN * RANDOM.nextDouble();
ox2 = x2 - CORNER_MARGIN * RANDOM.nextDouble(); // top right
oy2 = y1 + CORNER_MARGIN * RANDOM.nextDouble();
ox3 = x1 + CORNER_MARGIN * RANDOM.nextDouble(); // bottom left
oy3 = y2 - CORNER_MARGIN * RANDOM.nextDouble();
ox4 = x2 - CORNER_MARGIN * RANDOM.nextDouble(); // bottom right
oy4 = y2 - CORNER_MARGIN * RANDOM.nextDouble();
// Calculate the center of the polygon
double cx = (ox2 - ox1) / 2;
double cy = (oy2 - oy1) / 2;
// difference between window's center and polygon
double offsetX = centerX - cx;
double offsetY = centerY - cy;
// offset the calculated points so the polygon's center matches the window
ox1 += offsetX;
oy1 += offsetY;
ox2 += offsetX;
oy2 += offsetY;
ox3 += offsetX;
oy3 += offsetY;
ox4 += offsetX;
oy4 += offsetY;
// this is a standard polygon "centered" in the middle of the program window
return new double[]{
ox1, oy1,
ox2, oy2,
ox3, oy3,
ox4, oy4
};
}
public double distance(double x, double y, double x2, double y2) {
// r is earth’s radius (mean radius = 6,371km)
double r = 6371e3;
double toMile = 0.000621371;
double latDiff = x2 - x;
double lonDiff = y2 - y;
// a is the square of half the chord length between the points
double a = (Math.sin(latDiff/2) * Math.sin(latDiff/2)) + (Math.cos(x) * Math.cos(x2) * Math.sin(lonDiff/2) * Math.sin(lonDiff/2));
// c is the angular distance in radians
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
// d is the distance between to points
double d = r * c * toMile;
return d;
}
System.out.println(distance(41.386263640000003, -81.494450689999994, 42.531041999999999, -82.90854831));
This print statement gives me 4148.871894445495 miles whereas I checked through google map its distance is 193 miles. Can someone explain why is this so.
Thank you.
Well, you forgot to convert to radians :
public double distance(double x, double y, double x2, double y2) {
// r is earth’s radius (mean radius = 6,371km)
double r = 6371e3;
double toMile = 0.000621371;
double latDiff = (x2 - x)*(Math.PI)/180;
double lonDiff = (y2 - y)*(Math.PI)/180;;
// a is the square of half the chord length between the points
double a = (Math.sin(latDiff/2) * Math.sin(latDiff/2)) + (Math.cos(x) * Math.cos(x2) * Math.sin(lonDiff/2) * Math.sin(lonDiff/2));
// c is the angular distance in radians
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
// d is the distance between to points
double d = r * c * toMile;
return d;
}
Have a look here : https://www.movable-type.co.uk/scripts/latlong.html
I have this code:
void drawCircle(int x, int y, int r, int color) {
double PI = 3.1415926535;
double i, angle, x1, y1;
for (i = 0; i < 360; i += 1) {
angle = i;
x1 = r * cos(angle * PI / 180);
y1 = r * sin(angle * PI / 180);
int ElX = (int) (x + x1);
int ElY = (int) (y + y1);
myPixelElements[ElX][ElY].setElementColor(color);
}
}
It almost works but for some reason it draws 2 dots wrong:
cos and sin functions produce double values from -1 to +1, and when you cast double to int like this: int ElX = (int) (x + x1), some data will be inevitably lost, because such cast just chops the decimal part away. Instead, I suggest rounding double with Math.round, check example below:
System.out.println((int) 0.99); // 0
System.out.println((int) -0.99); // 0
System.out.println(Math.round(0.99)); // 1
System.out.println(Math.round(-0.99)); // -1
Note that Math.round returns long, so it still must be casted to int:
int ElX = (int) Math.round(x + x1);
int ElY = (int) Math.round(y + y1);
Output
Before After
****** *****
* * *** ***
* * * *
* * ** **
* * * *
* ** * *
* * * *
* * ** **
* * * *
****** *** ***
* *****
You're doing integer division in these lines:
x1 = r * cos(angle * PI / 180);
y1 = r * sin(angle * PI / 180);
A couple things are going on here. First, the integer division issue (change 180 to 180.0 to get a quick fix there). Second, you're doing the whole PI / 180.0 calculation every time through the loop - try pulling it out into its own variable:
double degToRadFactor = 3.1415926535 / 180.0
// ...
x1 = r * cos(angle * degToRadFactor)
y1 = r * sin(angle * degToRadFactor)
I am almost new to Java programming. I want to implement the following code in MATSim (it is a simulation programme for urban planning purposes). This code is about converting WGS84 (longitude and latitude) to OSGB36 (British National Grid).
https://gist.github.com/schoenobates/3497544#file-osgb-java
The MATSim library has an interface (below) to put the conversion codes in it and use it for visual simulation.
I have already tried many times to deal with errors, but it doesn't work me. Would you please give me some ideas about how I can do this.
package org.matsim.core.utils.geometry;
import org.matsim.api.core.v01.Coord;
/**
* A simple interface to convert coordinates from one coordinate system to
* another one.
*
* #author mrieser
*/
public interface CoordinateTransformation {
/**
* Transforms the given coordinate from one coordinate system to the other.
*
* #param coord The coordinate to transform.
* #return The transformed coordinate.
*/
public Coord transform(Coord coord);
}
Thank you, Somayeh
Ok, the error are here:
I did the below:
It is giving me two syntax errors:
double[] eastANDnorth(double lat, double lon) { for curly parenthesis and comma;
and
return new double(OSGB36N, OSGB36E); for double
package org.matsim.core.utils.geometry.transformations;
import org.matsim.api.core.v01.Coord;
import org.matsim.core.utils.geometry.CoordImpl;
import org.matsim.core.utils.geometry.CoordinateTransformation;
public class WGS84toOSGB36 implements CoordinateTransformation {
#Override
public Coord transform(Coord coord) {
// WGS84 ELLIPSOID
double WGS84_A = 6378137;
double WGS84_B = 6356752.314245;
double WGS84_E2 = ((WGS84_A * WGS84_A) - (WGS84_B * WGS84_B) / (WGS84_A * WGS84_A));
// NstGrid scale factor on central meridian
final double F0 = 0.9996012717;
// Airy 1830 major & minor semi-axes - note .909 not .910
final double AIRY_A = 6377563.396;
final double AIRY_B = 6356256.909;
// NatGrid true origin
final double LAT0 = Math.toRadians(49); //Phi0
final double LON0 = Math.toRadians(-2); //Lamda0
// northing & easting of true origin, metres
final double N0 = -100000;
final double E0 = 400000;
// eccentricity squared
final double E2 = ((AIRY_A * AIRY_A) - (AIRY_B * AIRY_B)) / (AIRY_A *AIRY_A);
final double N = (AIRY_A - AIRY_B) / (AIRY_A + AIRY_B);
final double N2 = N * N;
final double N3 = N * N * N;
final double TX = -446.448;
final double TY = 125.157;
final double TZ = -542.060;
final double RX = Math.toRadians(-0.1502 / 3600);
final double RY = Math.toRadians(-0.2470 / 3600);
final double RZ = Math.toRadians(-0.8421 / 3600);
final double S = 20.4894 / 1e6 + 1;
/*----*/double[] eastANDnorth(double lat, double lon) {/* error in this line */
// -- 1: convert polar to cartesian coordinates (using ellipse 1)
// WGS84 ellipsoid
double sinPhi = Math.sin(lat);
double cosPhi = Math.cos(lat);
double sinLambda = Math.sin(lon);
double cosLambda = Math.cos(lon);
double H = 24.7; // for the moment
double nu = WGS84_A / Math.sqrt(1 - WGS84_E2 * sinPhi * sinPhi);
double x1 = (nu + H) * cosPhi * cosLambda;
double y1 = (nu + H) * cosPhi * sinLambda;
double z1 = ((1-WGS84_E2) * nu + H) * sinPhi;
// -- 2: apply helmert transform using appropriate params
double x2 = TX + x1 * S - y1 * RZ + z1 * RY;
double y2 = TY + x1 * RZ + y1 * S - z1 * RX;
double z2 = TZ - x1 * RY + y1 * RX + z1 * S;
// -- 3: convert cartesian to polar coordinates (using ellipse 2)
double precision = 4 / AIRY_A;
double p = Math.sqrt(x2 * x2 + y2 * y2);
double phi = Math.atan2(z2, p * (1 - E2)), phiP = 2 * Math.PI;
while (Math.abs(phi - phiP) > precision) {
nu = AIRY_A / Math.sqrt(1 - E2 * Math.sin(phi) * Math.sin(phi));
phiP = phi;
phi = Math.atan2(z2 + E2 * nu * Math.sin(phi), p);
}
double lambda = Math.atan2(y2, x2);
// -- 4: now we're in OSGB, get the EN coords
double cosLat = Math.cos(phi), sinLat = Math.sin(phi);
nu = AIRY_A * F0 / Math.sqrt(1 - E2 * sinLat * sinLat);
double rho = AIRY_A * F0 * (1 - E2) / Math.pow(1 - E2 * sinLat * sinLat, 1.5);
double eta2 = nu / rho - 1;
double Ma = (1 + N + (5 / 4) * N2 + (5 / 4) * N3) * (phi - LAT0);
double Mb = (3 * N + 3 * N * N + (21 / 8) * N3) * Math.sin(phi - LAT0) * Math.cos(phi + LAT0);
double Mc = ((15 / 8) * N2 + (15 / 8) * N3) * Math.sin(2 * (phi - LAT0)) * Math.cos(2 * (phi + LAT0));
double Md = (35 / 24) * N3 * Math.sin(3 * (phi - LAT0)) * Math.cos(3 * (phi + LAT0));
double M = AIRY_B * F0 * (Ma - Mb + Mc - Md); // meridional arc
double cos3lat = cosLat * cosLat * cosLat;
double cos5lat = cos3lat * cosLat * cosLat;
double tan2lat = Math.tan(phi) * Math.tan(phi);
double tan4lat = tan2lat * tan2lat;
double I = M + N0;
double II = (nu / 2) * sinLat * cosLat;
double III = (nu / 24) * sinLat * cos3lat * (5 - tan2lat + 9 * eta2);
double IIIA = (nu / 720) * sinLat * cos5lat * (61 - 58 * tan2lat + tan4lat);
double IV = nu * cosLat;
double V = (nu / 6) * cos3lat * (nu / rho - tan2lat);
double VI = (nu / 120) * cos5lat * (5 - 18 * tan2lat + tan4lat + 14 * eta2 - 58 * tan2lat * eta2);
double dLon = lambda - LON0;
double dLon2 = dLon * dLon, dLon3 = dLon2 * dLon, dLon4 = dLon3 * dLon, dLon5 = dLon4 * dLon, dLon6 = dLon5 * dLon;
double OSGB36N = I + II * dLon2 + III * dLon4 + IIIA * dLon6;
double OSGB36E = E0 + IV * dLon + V * dLon3 + VI * dLon5;
/*--------*/return new double(OSGB36N, OSGB36E);/* error in this line */
}
return new CoordImpl(OSGB36N, OSGB36E);
}
}
You are trying to create a array with this expression:
new double(OSGB36N, OSGB36E)
However that's invalid java syntax. You should change it to
new double[]{ OSGB36N, OSGB36E }
Also your're trying to declare a method inside another method, i.e. eastANDnorth inside transform, which is not valid in java.
I am wanting to find the distance between two different points. This I know can be accomplished with the great circle distance.
http://www.meridianworlddata.com/Distance-calculation.asp
Once done, with a point and distance I would like to find the point that distance north, and that distance east in order to create a box around the point.
Here is a Java implementation of Haversine formula. I use this in a project to calculate distance in miles between lat/longs.
public static double distFrom(double lat1, double lng1, double lat2, double lng2) {
double earthRadius = 3958.75; // miles (or 6371.0 kilometers)
double dLat = Math.toRadians(lat2-lat1);
double dLng = Math.toRadians(lng2-lng1);
double sindLat = Math.sin(dLat / 2);
double sindLng = Math.sin(dLng / 2);
double a = Math.pow(sindLat, 2) + Math.pow(sindLng, 2)
* Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2));
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
double dist = earthRadius * c;
return dist;
}
Or you could use SimpleLatLng. Apache 2.0 licensed and used in one production system that I know of: mine.
Short story:
I was searching for a simple geo library and couldn't find one to fit my needs. And who wants to write and test and debug these little geo tools over and over again in every application? There's got to be a better way!
So SimpleLatLng was born as a way to store latitude-longitude data, do distance calculations, and create shaped boundaries.
I know I'm two years too late to help the original poster, but my aim is to help the people like me who find this question in a search. I would love to have some people use it and contribute to the testing and vision of this little lightweight utility.
We've had some success using OpenMap to plot a lot of positional data. There's a LatLonPoint class that has some basic functionality, including distance.
For a more accurate distance (0.5mm) you can also use the Vincenty approximation:
/**
* Calculates geodetic distance between two points specified by latitude/longitude using Vincenty inverse formula
* for ellipsoids
*
* #param lat1
* first point latitude in decimal degrees
* #param lon1
* first point longitude in decimal degrees
* #param lat2
* second point latitude in decimal degrees
* #param lon2
* second point longitude in decimal degrees
* #returns distance in meters between points with 5.10<sup>-4</sup> precision
* #see Originally posted here
*/
public static double distVincenty(double lat1, double lon1, double lat2, double lon2) {
double a = 6378137, b = 6356752.314245, f = 1 / 298.257223563; // WGS-84 ellipsoid params
double L = Math.toRadians(lon2 - lon1);
double U1 = Math.atan((1 - f) * Math.tan(Math.toRadians(lat1)));
double U2 = Math.atan((1 - f) * Math.tan(Math.toRadians(lat2)));
double sinU1 = Math.sin(U1), cosU1 = Math.cos(U1);
double sinU2 = Math.sin(U2), cosU2 = Math.cos(U2);
double sinLambda, cosLambda, sinSigma, cosSigma, sigma, sinAlpha, cosSqAlpha, cos2SigmaM;
double lambda = L, lambdaP, iterLimit = 100;
do {
sinLambda = Math.sin(lambda);
cosLambda = Math.cos(lambda);
sinSigma = Math.sqrt((cosU2 * sinLambda) * (cosU2 * sinLambda)
+ (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda) * (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda));
if (sinSigma == 0)
return 0; // co-incident points
cosSigma = sinU1 * sinU2 + cosU1 * cosU2 * cosLambda;
sigma = Math.atan2(sinSigma, cosSigma);
sinAlpha = cosU1 * cosU2 * sinLambda / sinSigma;
cosSqAlpha = 1 - sinAlpha * sinAlpha;
cos2SigmaM = cosSigma - 2 * sinU1 * sinU2 / cosSqAlpha;
if (Double.isNaN(cos2SigmaM))
cos2SigmaM = 0; // equatorial line: cosSqAlpha=0 (§6)
double C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
lambdaP = lambda;
lambda = L + (1 - C) * f * sinAlpha
* (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)));
} while (Math.abs(lambda - lambdaP) > 1e-12 && --iterLimit > 0);
if (iterLimit == 0)
return Double.NaN; // formula failed to converge
double uSq = cosSqAlpha * (a * a - b * b) / (b * b);
double A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
double B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
double deltaSigma = B
* sinSigma
* (cos2SigmaM + B
/ 4
* (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) - B / 6 * cos2SigmaM
* (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
double dist = b * A * (sigma - deltaSigma);
return dist;
}
This code was freely adapted from http://www.movable-type.co.uk/scripts/latlong-vincenty.html
Corrected Haversine Distance formula....
public static double HaverSineDistance(double lat1, double lng1, double lat2, double lng2)
{
// mHager 08-12-2012
// http://en.wikipedia.org/wiki/Haversine_formula
// Implementation
// convert to radians
lat1 = Math.toRadians(lat1);
lng1 = Math.toRadians(lng1);
lat2 = Math.toRadians(lat2);
lng2 = Math.toRadians(lng2);
double dlon = lng2 - lng1;
double dlat = lat2 - lat1;
double a = Math.pow((Math.sin(dlat/2)),2) + Math.cos(lat1) * Math.cos(lat2) * Math.pow(Math.sin(dlon/2),2);
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
return EARTH_RADIUS * c;
}
http://www.movable-type.co.uk/scripts/latlong.html
public static Double distanceBetweenTwoLocationsInKm(Double latitudeOne, Double longitudeOne, Double latitudeTwo, Double longitudeTwo) {
if (latitudeOne == null || latitudeTwo == null || longitudeOne == null || longitudeTwo == null) {
return null;
}
Double earthRadius = 6371.0;
Double diffBetweenLatitudeRadians = Math.toRadians(latitudeTwo - latitudeOne);
Double diffBetweenLongitudeRadians = Math.toRadians(longitudeTwo - longitudeOne);
Double latitudeOneInRadians = Math.toRadians(latitudeOne);
Double latitudeTwoInRadians = Math.toRadians(latitudeTwo);
Double a = Math.sin(diffBetweenLatitudeRadians / 2) * Math.sin(diffBetweenLatitudeRadians / 2) + Math.cos(latitudeOneInRadians) * Math.cos(latitudeTwoInRadians) * Math.sin(diffBetweenLongitudeRadians / 2)
* Math.sin(diffBetweenLongitudeRadians / 2);
Double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
return (earthRadius * c);
}
You can use the Java Geodesy Library for GPS, it uses the Vincenty's formulae which takes account of the earths surface curvature.
Implementation goes like this:
import org.gavaghan.geodesy.*;
...
GeodeticCalculator geoCalc = new GeodeticCalculator();
Ellipsoid reference = Ellipsoid.WGS84;
GlobalPosition pointA = new GlobalPosition(latitude, longitude, 0.0);
GlobalPosition userPos = new GlobalPosition(userLat, userLon, 0.0);
double distance = geoCalc.calculateGeodeticCurve(reference, userPos, pointA).getEllipsoidalDistance();
The resulting distance is in meters.
This method would help you find the distance between to geographic location in km.
private double getDist(double lat1, double lon1, double lat2, double lon2)
{
int R = 6373; // radius of the earth in kilometres
double lat1rad = Math.toRadians(lat1);
double lat2rad = Math.toRadians(lat2);
double deltaLat = Math.toRadians(lat2-lat1);
double deltaLon = Math.toRadians(lon2-lon1);
double a = Math.sin(deltaLat/2) * Math.sin(deltaLat/2) +
Math.cos(lat1rad) * Math.cos(lat2rad) *
Math.sin(deltaLon/2) * Math.sin(deltaLon/2);
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
double d = R * c;
return d;
}
Kotlin version of Haversine formula. Returned result in meters. Tested on https://www.vcalc.com/wiki/vCalc/Haversine+-+Distance
const val EARTH_RADIUS_IN_METERS = 6371007.177356707
fun distance(lat1: Double, lng1: Double, lat2: Double, lng2: Double): Double {
val latDiff = Math.toRadians(abs(lat2 - lat1))
val lngDiff = Math.toRadians(abs(lng2 - lng1))
val a = sin(latDiff / 2) * sin(latDiff / 2) +
cos(Math.toRadians(lat1)) * cos(Math.toRadians(lat2)) *
sin(lngDiff / 2) * sin(lngDiff / 2)
val c = 2 * atan2(sqrt(a), sqrt(1 - a))
return EARTH_RADIUS_IN_METERS * c
}
I know that there are many answers, but in doing some research on this topic, I found that most answers here use the Haversine formula, but the Vincenty formula is actually more accurate. There was one post that adapted the calculation from a Javascript version, but it's very unwieldy. I found a version that is superior because:
It also has an open license.
It uses OOP principles.
It has greater flexibility to choose the ellipsoid you want to use.
It has more methods to allow for different calculations in the future.
It is well documented.
VincentyDistanceCalculator
I typically use MATLAB with the Mapping Toolbox, and then use the code in my Java using MATLAB Builder JA. It makes my life a lot simpler. Given most schools have it for free student access, you can try it out (or get the trial version to get over your work).
For Android, there is a simple approach.
public static float getDistanceInMeter(LatLng start, LatLng end) {
float[] results = new float[1];
Location.distanceBetween(start.latitude, start.longitude, end.latitude, end.longitude, results);
return results[0];
}
;
https://developer.android.com/reference/android/location/Location#distanceBetween(lat1,lng1,lat2,lng2,output[])