jemz
July 14, 2014, 7:05am
1
I plot marker on map as boundary, and every time I click in a certain location of map I get the latlang coordinates and save it to my database,

this is the sample coordinates that was saved in my database

53.198526418064645,-105.76238214969635
53.198564980328875,-105.76508045196533
53.199002016899044,-105.76231241226196
53.19939406061905,-105.76508045196533
53.19941012790812,-105.76509118080139
53.19941976827867,-105.76212465763092
53.199426195191194,-105.76357841491699

Now I want that if the user passes each coordinate or gets inside 5 meters perimeter of each coordinates it will prompt like this, the user “get’s in” or “get’s out” in the area.but i have no idea how do i achieve like this to detect if the user passes or get inside in this 5 meters peremeter in each coordinates.is this possible?

I followed this example approach

but i got an error,Math.radians is not a function!

this is my code

```
function geofence(){
/****this is the latng coordinates user's tracker location*****/
$lat = 53.199425;//this is the lat user's tracker
$lng = -105.763580;//this is the lng user's tracker
/*****************************************************************/
//here i don't know how to put 5 meters radius.and i get error in using Math.radians is not a function.
$distance = 3959 * Math.acos( Math.cos( Math.radians(53.199425) ) * Math.cos( radians( $lat ) ) * Math.cos( Math.radians( $lng ) - Math.radians(-105.763580) ) + Math.sin( Math.radians(53.199425) ) * Math.sin( Math.radians( $lat ) ) );
console.log("Alert distance",$distance);
}
```

can you help me please.

Radians are worked out by multiplying the degrees angle by Tau over 360.

```
function radians(degrees) {
var TAU = 2 * Math.PI;
return degrees * TAU / 360;
}
```

Or, now that Brendan Eich is going to champion the inclusion of Math.TAU , I’ve been taking to doing the following instead:

```
if (!Math.TAU) {
Math.TAU = 2 * Math.PI;
}
// ...
function radians(degrees) {
return degrees * Math.TAU / 360;
}
```

Yes, you could just use Math.PI/180, but to me it just seems to be counter-intuitive to use half a circle to convert degrees around a circle.

jemz
July 14, 2014, 8:54am
3

paul_wilkins:

Radians are worked out by multiplying the degrees angle by Tau over 360.

```
function radians(degrees) {
var TAU = 2 * Math.PI;
return degrees * TAU / 360;
}
```

Or, now that Brendan Eich is going to champion the inclusion of Math.TAU , I’ve been taking to doing the following instead:

```
if (!Math.TAU) {
Math.TAU = 2 * Math.PI;
}
// ...
function radians(degrees) {
return degrees * Math.TAU / 360;
}
```

Yes, you could just use Math.PI/180, but to me it just seems to be counter-intuitive to use half a circle to convert degrees around a circle.

Hi paul,

Thank you for the quick reply,I am just confuse how can i apply the 5 meters in my code?

Thank you in advance.

JavaScript doesn’t have a Math.radians function.

Instead, you need to supply your own, called radians

```
function radians(degrees) {
var TAU = 2 * Math.PI;
return degrees * TAU / 360;
}
```

Once you have that function, you can use it to convert degrees into radians, for example:

```
radians(53.199425); // 0.9285051264177843
```

So include that radians function, change any Math.radians(…) function calls to be instead radians(…) and you should be fine.

jemz
July 14, 2014, 11:43am
5

paul_wilkins:

JavaScript doesn’t have a Math.radians function.

Instead, you need to supply your own, called radians

```
function radians(degrees) {
var TAU = 2 * Math.PI;
return degrees * TAU / 360;
}
```

Once you have that function, you can use it to convert degrees into radians, for example:

```
radians(53.199425); // 0.9285051264177843
```

So include that radians function, change any Math.radians(…) function calls to be instead radians(…) and you should be fine.

Hi paul,thanks i got exactly same output of your comment…can i ask do i need to covert the 3959 into meter ?

Only if you want the answer in metres.
Look at the Great circle page and you will see that the number is the radius of the earth.

jemz
July 15, 2014, 1:47am
7
Hi paul,ok so i will change it to meters,so if i want 5 meters , i will just do this

if (distance <5){
alert(“5 meters”);
}

please correct me if i am wrong.

Thank you in advance.

jemz:

Hi paul,ok so i will change it to meters,so if i want 5 meters , i will just do this

if (distance <5){
alert(“5 meters”);
}

Yea, though it would be more accurate if you said that they are within 5 metres.