I'm using Leaflet.js to save coverage maps and am giving the user the option of using polygons or circles.
To keep all objects in the same format, I'm converting the circle to a polygon before saving.
However, when I then reload the circle it is oval-shaped.
I know that this is due to the earth's curve but I'm unsure how to correct my method to take this into account? (I've looked but can't find anything that gives the solution I'm after).
The main issue is the javascript method I'm using below as that doesn't take into account the earth's curve.
// GenerateCirlcePolygon - Creates Circle from 360 line Segments
function GenerateCirlcePolygon(origin, radius) {
var earthRadius = 6371;
//latitude in radians
var lat = (origin.Latitude * Math.PI) / 180;
//longitude in radians
var lon = (origin.Longitude * Math.PI) / 180;
//angular distance covered on earth's surface
var d = parseFloat(radius) / earthRadius;
polyPoints = new Array();
for (i = 0; i <= 360; i++) {
var point = new VELatLong(0, 0)
var bearing = i * Math.PI / 180; //rad
point.Latitude = Math.asin(Math.sin(lat) * Math.cos(d) + Math.cos(lat) * Math.sin(d) * Math.cos(bearing));
point.Longitude = ((lon + Math.atan2(Math.sin(bearing) * Math.sin(d) * Math.cos(lat), Math.cos(d) - Math.sin(lat) * Math.sin(point.Latitude))) * 180) / Math.PI;
point.Latitude = (point.Latitude * 180) / Math.PI;
polyPoints.push(point);
}
Any advice at all would be great.
You can use the built in function from leaflet-geoman: L.PM.Utils.circleToPolygon(circle, sides)
L.PM.Utils.circleToPolygon(circle, 60).addTo(map)
I'm developing a simple jQuery / Phonegap app and I'm using watchPosition to constantly calculate between the distance current location and some remote place. This works just fine, but this is my issue. I would like to trigger an event (function) when the distance is less than a mile from that location. The way I have it right now it would continue triggering the event as long as the distance is less than a mile. What can I do to "tell" watchPosition to trigger the event only once and continue watching my position?
I included what I consider the relevant part of the code for your reference.
Success portion of watchPosition:
var remoteLat = xx.xxxx;
var remoteLng = xx.xxxx;
function onSuccess(position) {
var myLat = position.coords.latitude;
var myLng = position.coords.longitude;
var distancia = gps_distance(myLat, myLng, remoteLat, remoteLng);
if (distancia < 1) {
alert('Almost There');
playSound();
}
}
Distance calculating function:
function gps_distance(lat1, lon1, lat2, lon2) {
var R = 3959; // use 3959 for miles or 6371 for km
var dLat = (lat2 - lat1) * (Math.PI / 180);
var dLon = (lon2 - lon1) * (Math.PI / 180);
var lat1 = lat1 * (Math.PI / 180);
var lat2 = lat2 * (Math.PI / 180);
var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1) * Math.cos(lat2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
var d = R * c;
return d;
}
If more of the code is necessary, please let me know. I also would like to give credit to this question previously asked about calculating distances Link . Thanks!
Just use a flag to track the alert.
var alerFlag = true;
if (distancia < 1 && alerFlag == true) {
alert('Almost There');
playSound();
alerFlag = false;
}else{
alerFlag = true; // This is for whenever you go greater than 1 mi
}
I have an array with coordinates in and want to add them up to determine a total distance (not just from point A to point B).
My array is structured as latitude1, longitude1, latitude2, longitude2 and so on.
I have to code to actually work out the distance (shown below), but don't know how to do the loop needed to get the coordinates.
function distance(lat1, lon1, lat2, lon2) {
var R = 6371;
var a =
0.5 - Math.cos((lat2 - lat1) * Math.PI / 180)/2 +
Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
(1 - Math.cos((lon2 - lon1) * Math.PI / 180))/2;
return R * 2 * Math.asin(Math.sqrt(a));
}
How should the loop be done?
Thanks.
There are several ways, I would do it like this:
int sum(int[] array) {
int sum = 0;
for(int i = 0; i < array.size(); i++) {
sum += distance(array[i], array[i+1], array[i+2], array[i+3]);
i +=4;
}
return sum;
}
I have a function to calculate the distance between two sets of latitude and longitude coordinates I get from the Google Maps API
Here is the calculate distance function:
function getDistance(lat1, lon1, lat2, lon2) {
var lat1p = parseFloat(lat1);
var lon1p = parseFloat(lon1);
var lat2p = parseFloat(lat2);
var lon2p = parseFloat(lon2);
var R = 6371; // km (change this constant to get miles)
var dLat = (lat2p-lat1p) * Math.PI / 180;
var dLon = (lon2p-lon1p) * Math.PI / 180;
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1 * Math.PI / 180 ) * Math.cos(lat2 * Math.PI / 180 ) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
if (d>1) return Math.round(d)+"km";
else if (d<=1) return Math.round(d*1000)+"m";
return d;
}
I believe all the coordinates are considered Float types I'm not 100% sure but when I have it print or alert what the distance is it returns NaN.... Is there a way to do this. I'm trying to stray away from the Google Maps API to calculate distance because that would make everything harder because I would essentially have to start over.
I'm sorry I fixed it I was double declaring variables as well as I had a . instead of a , when I called the distance function. Thank you guys for your suggestions they led me to figure it out.
I'm trying to use the Haversine Distance Formula (as found here: http://www.movable-type.co.uk/scripts/latlong.html) but I can't get it to work, please see the following code
function test() {
var lat2 = 42.741;
var lon2 = -71.3161;
var lat1 = 42.806911;
var lon1 = -71.290611;
var R = 6371; // km
//has a problem with the .toRad() method below.
var dLat = (lat2-lat1).toRad();
var dLon = (lon2-lon1).toRad();
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
alert(d);
}
And the error is:
Uncaught TypeError: Object -0.06591099999999983 has no method 'toRad'
Which I understand to be because it needs to do the following:
Number.prototype.toRad = function() {
return this * Math.PI / 180;
}
But when I put this below the function, it still comes back with the same error message. How do I make it use the helper method? Or is there an alternative way to code this to get it to work? Thanks!
This code is working:
Number.prototype.toRad = function() {
return this * Math.PI / 180;
}
var lat2 = 42.741;
var lon2 = -71.3161;
var lat1 = 42.806911;
var lon1 = -71.290611;
var R = 6371; // km
//has a problem with the .toRad() method below.
var x1 = lat2-lat1;
var dLat = x1.toRad();
var x2 = lon2-lon1;
var dLon = x2.toRad();
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;
alert(d);
Notice how I defined x1 and x2.
Play with it at: https://tinker.io/3f794
Here's a refactored function based on 3 of the other answers!
Please note that the coords arguments are [longitude, latitude].
function haversineDistance(coords1, coords2, isMiles) {
function toRad(x) {
return x * Math.PI / 180;
}
var lon1 = coords1[0];
var lat1 = coords1[1];
var lon2 = coords2[0];
var lat2 = coords2[1];
var R = 6371; // km
var x1 = lat2 - lat1;
var dLat = toRad(x1);
var x2 = lon2 - lon1;
var dLon = toRad(x2)
var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) *
Math.sin(dLon / 2) * Math.sin(dLon / 2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
var d = R * c;
if(isMiles) d /= 1.60934;
return d;
}
ES6 JavaScript/NodeJS refactored version:
/**
* Calculates the haversine distance between point A, and B.
* #param {number[]} latlngA [lat, lng] point A
* #param {number[]} latlngB [lat, lng] point B
* #param {boolean} isMiles If we are using miles, else km.
*/
const haversineDistance = ([lat1, lon1], [lat2, lon2], isMiles = false) => {
const toRadian = angle => (Math.PI / 180) * angle;
const distance = (a, b) => (Math.PI / 180) * (a - b);
const RADIUS_OF_EARTH_IN_KM = 6371;
const dLat = distance(lat2, lat1);
const dLon = distance(lon2, lon1);
lat1 = toRadian(lat1);
lat2 = toRadian(lat2);
// Haversine Formula
const a =
Math.pow(Math.sin(dLat / 2), 2) +
Math.pow(Math.sin(dLon / 2), 2) * Math.cos(lat1) * Math.cos(lat2);
const c = 2 * Math.asin(Math.sqrt(a));
let finalDistance = RADIUS_OF_EARTH_IN_KM * c;
if (isMiles) {
finalDistance /= 1.60934;
}
return finalDistance;
};
See codepen for tests against accepted answer: https://codepen.io/harrymt/pen/dyYvLpJ?editors=1011
Why not try the straight forward solution? Instead of extending Number prototype, just define toRad as a regular function:
function toRad(x) {
return x * Math.PI / 180;
}
and then call toRad everywhere:
var dLat = toRad(lat2-lat1);
Extending the Number prototype does not always work as expected. For example calling 123.toRad() does not work. I think that if you do var x1 = lat2 - lat1; x1.toRad(); works better than doing (lat2-lat1).toRad()
when I put this below the function
You only need to put it above the point where you call test(). Where the test function itself is declared does not matter.
You need to extend the Number prototype, before calling those extensions in a function.
So just ensure
Number.prototype.toRad = function() {
return this * Math.PI / 180;
}
is called before your function is called.
Another variant to reduce redundancy and also compatible with Google LatLng objects:
function haversine_distance(coords1, coords2) {
function toRad(x) {
return x * Math.PI / 180;
}
var dLat = toRad(coords2.latitude - coords1.latitude);
var dLon = toRad(coords2.longitude - coords1.longitude)
var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
Math.cos(toRad(coords1.latitude)) *
Math.cos(toRad(coords2.latitude)) *
Math.sin(dLon / 2) * Math.sin(dLon / 2);
return 12742 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
}
Here's another refactored answer in JavaScript:
getHaversineDistance = (firstLocation, secondLocation) => {
const earthRadius = 6371; // km
const diffLat = (secondLocation.lat-firstLocation.lat) * Math.PI / 180;
const diffLng = (secondLocation.lng-firstLocation.lng) * Math.PI / 180;
const arc = Math.cos(
firstLocation.lat * Math.PI / 180) * Math.cos(secondLocation.lat * Math.PI / 180)
* Math.sin(diffLng/2) * Math.sin(diffLng/2)
+ Math.sin(diffLat/2) * Math.sin(diffLat/2);
const line = 2 * Math.atan2(Math.sqrt(arc), Math.sqrt(1-arc));
const distance = earthRadius * line;
return distance;
}
const philly = { lat: 39.9526, lng: -75.1652 }
const nyc = { lat: 40.7128, lng: -74.0060 }
const losAngeles = { lat: 34.0522, lng: -118.2437 }
console.log(getHaversineDistance(philly, nyc)) //129.61277152662188
console.log(getHaversineDistance(philly, losAngeles)) //3843.4534005980404
This is a java implemetation of talkol's solution above. His or her solution worked very well for us. I'm not trying to answer the question, since the original question was for javascript. I'm just sharing our java implementation of the given javascript solution in case others find it of use.
// this was a pojo class we used internally...
public class GisPostalCode {
private String country;
private String postalCode;
private double latitude;
private double longitude;
// getters/setters, etc.
}
public static double distanceBetweenCoordinatesInMiles2(GisPostalCode c1, GisPostalCode c2) {
double lat2 = c2.getLatitude();
double lon2 = c2.getLongitude();
double lat1 = c1.getLatitude();
double lon1 = c1.getLongitude();
double R = 6371; // km
double x1 = lat2 - lat1;
double dLat = x1 * Math.PI / 180;
double x2 = lon2 - lon1;
double dLon = x2 * Math.PI / 180;
double a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1*Math.PI/180) * Math.cos(lat2*Math.PI/180) *
Math.sin(dLon/2) * Math.sin(dLon/2);
double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
double d = R * c;
// convert to miles
return d / 1.60934;
}