hello i have this function
locDistance(alat[i-1], alon[i-1], alat[i], alon[i]);
function locDistance(lat1, lon1, lat2, lon2) {
//Radius of the earth in: 1.609344 miles, 6371 km | var R = (6371 / 1.609344);
//var R = 3958.7558657440545;
var R = 3958.7558657440545;
var dLat = toRad(lat2-lat1);
var dLon = toRad(lon2-lon1);
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;
var dist = d;
};
function toRad(Value) {
/** Converts numeric degrees to radians */
return Value * Math.PI / 180;
}
i know i have to declare the variable outside the function to use it at another place
so i have defined at the top of the page
var dist = 0;
i want to use de variable 'dist' in another function like in here
$('.content').append(dist);
but the problem is i keep getting 0 as result of the dist variable.
i have checked but inside de locDistance function the dist variable has different values as it should be so the function is not the issue here
what am i doing wrong?
thank you in advance
The reason that the code above does not work is that the var keyword is being used in the locDistance method, thereby setting dist to a local variable every time the function is called and leaving the global dist set to 0.
That being said...
Perhaps you would rather have locDistance return the value and then call the function when you need it, like:
$('.content').append(locDistance(alat[i-1], alon[i-1], alat[i], alon[i]));
function locDistance(lat1, lon1, lat2, lon2) {
//Radius of the earth in: 1.609344 miles, 6371 km | var R = (6371 / 1.609344);
//var R = 3958.7558657440545;
var R = 3958.7558657440545;
var dLat = toRad(lat2-lat1);
var dLon = toRad(lon2-lon1);
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;
return d;
}
function toRad(Value) {
/** Converts numeric degrees to radians */
return Value * Math.PI / 180;
}
Related
Hey guys can anybody help me why i am getting an error in this code
Here is the code.
getWithinDistance: function(){
var selectedMarker = [];
var lat1 = this.state.region.latitude;
var lon1 = this.state.region.longitude;
for(var i = 0 ; i <= 3 ; i++)
{
var lat2 = this.state.a[i].latitude;
var lon2 = this.state.a[i].longitude;
var R = 6371;
var dLat = (lat2-lat1) * (Math.PI/180);
var dLon = (lon2-lon1) * (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 <= 2.00){
var latlng = {
latitude: lat2,
longitude: lon2
}
selectedMarker.push(latlng);
}
}
console.log(selectedMarker);
var at = selectedMarker.map(marker => {
return(
<MapView.Marker coordinate={marker.latlng} />
);
})
},
I am getting Warning: Failed prop type: Required prop coordinate was not specified. but when i log it i can see two markers in the array selectedMarker[]
here is the snap of log which i get
Thanks in advance.
You have placed the return statement inside your for loop. So the the loop will exit after the first iteration.
Take these lines out of the for loop.
return (
<MapView.Marker coordinate={this.state.a[i]} />
);
Edit your for loop to store all the markers that are within the required distance in an array and then after the for loop return that array
You can use Array.prototype.map() to iterate and get the values.
Like this:
(ES6 Style)
getWithinDistance: function(){
const lat1 = this.state.region.latitude;
const lon1 = this.state.region.longitude;
const R = 6371
this.state.a.map(coordinate => {
const dLat = (coordinate.latitude - lat1) * (Math.PI/180)
const dLon = (coordinate.longitude - lon1) * (Math.PI/180)
const 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);
const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
const d = R * c
console.log(coordinate, d)
}
}
This will show the coordinates with their distance to your location.
The return statement has to be outside the map() function. And return whatever you want to achieve.
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 want to execute functions in order but i constantly get 1,3,4,2 in console.Because of that ltt and lott remains 0 in function getDistanceFromLatLonInKm.Any ideas?Thanks in advance.
var ltt=0;
var lott=0;
if (navigator.geolocation){
navigator.geolocation.getCurrentPosition(ajmo);
console.log('1');
}
function ajmo(position){
console.log('2');
window.ltt=position.coords.latitude;
window.lott=position.coords.longitude;
document.write(window.ltt);
}
console.log('3');
document.write(window.ltt);
document.write("kurac:" + getDistanceFromLatLonInKm(45.332497,14.436384));
function getDistanceFromLatLonInKm(lat1,lon1){
console.log('4');
//second
var R = 6371; // Radius of the earth in km
var dLat = deg2rad(ltt-lat1); // deg2rad below
var dLon = deg2rad(lott-lon1);
var a =
Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(ltt)) *
Math.sin(dLon/2) * Math.sin(dLon/2)
;
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c; // Distance in km
return d;
}
function deg2rad(deg) {
return deg * (Math.PI/180)
}
The following changes will ensure that all console messages are in order 1,2,3,4
var ltt=0;
var lott=0;
if (navigator.geolocation){
console.log('1');
navigator.geolocation.getCurrentPosition(ajmo);
}
function ajmo(position){
console.log('2');
window.ltt=position.coords.latitude;
window.lott=position.coords.longitude;
document.write(window.ltt);
console.log('3');
document.write(window.ltt);
document.write("kurac:" + getDistanceFromLatLonInKm(45.332497,14.436384));
}
function getDistanceFromLatLonInKm(lat1,lon1){
console.log('4');
//second
var R = 6371; // Radius of the earth in km
var dLat = deg2rad(ltt-lat1); // deg2rad below
var dLon = deg2rad(lott-lon1);
var a =
Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(ltt)) *
Math.sin(dLon/2) * Math.sin(dLon/2)
;
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c; // Distance in km
return d;
}
function deg2rad(deg) {
return deg * (Math.PI/180)
}
The reason why they are being called out of order is because the method "geolocation.getCurrentPosition(success, error, options)" is asynchronous.
https://developer.mozilla.org/en-US/docs/WebAPI/Using_geolocation
The (function)object AJMO that you are giving to it is actually used to describe the callback method. The script hits the line and sends an asynchronous request to the function, BUT it isn't going to wait for a response. The execution proceeds forward even though it hasn't heard back yet. The remaining lines are pretty simple with very low overhead so they resolve much, much quicker than the getCurrentPosition method. '2' is executed at the end, but this is only because the method finally "called back" to the success function you created, "AJMO".
If you want to make sure that the code is executed in order you could try this instead.
var ltt=0;
var lott=0;
function getDistanceFromLatLonInKm(lat1,lon1){
console.log('4');
//second
var R = 6371; // Radius of the earth in km
var dLat = deg2rad(ltt-lat1); // deg2rad below
var dLon = deg2rad(lott-lon1);
var a =
Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(ltt)) *
Math.sin(dLon/2) * Math.sin(dLon/2)
;
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c; // Distance in km
return d;
}
function ajmo(position){
console.log('2');
window.ltt=position.coords.latitude;
window.lott=position.coords.longitude;
document.write(window.ltt);
console.log('3');
document.write("kurac:" + getDistanceFromLatLonInKm(45.332497,14.436384));
}
if (navigator.geolocation){
navigator.geolocation.getCurrentPosition(ajmo);
console.log('1');
}
This puts the calls to '2', '3', and '4' within the successful callback method while still exposing "getDistanceFromLatLonInKm" as a separate function if you need it for some other purpose.
You don't need to use global variables here. Simply include the call to getDistanceFromLatLonInKm within ajmo, and this will ensure that your code does things in the right order.
// call getLocation
getLocation();
function getLocation() {
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(ajmo);
}
}
function ajmo(position) {
var lat = position.coords.latitude;
var lng = position.coords.longitude;
// don't use document.write - it's considered bad practice
// this will get access to an element with id="out"
var out = document.getElementById('out');
// now pass lat and lng as new parameters into getDistanceFromLatLonInKm
out.innerHTML = 'kurac:' + getDistanceFromLatLonInKm(45.332497, 14.436384, lat, lng);
}
// now use the lat/lng arguments instead of the global variables
function getDistanceFromLatLonInKm(lat_origin, lon_origin, lat_pos, lng_pos) {
var R = 6371;
var dLat = deg2rad(lat_pos - lat_origin);
var dLon = deg2rad(lng_pos - lng_origin);
var a =
Math.sin(dLat / 2) * Math.sin(dLat / 2) +
Math.cos(deg2rad(lat_origin)) * Math.cos(deg2rad(lat_pos)) *
Math.sin(dLon / 2) * Math.sin(dLon / 2)
;
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
var d = R * c;
return d;
}
function deg2rad(deg) {
return deg * (Math.PI/180)
}
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;
}