How to Build a Distance Finder with Google Maps API

Google maps is a free web mapping service application provided by Google. It offers lots of cool features (showing various map types, plotting points, showing routes, geocoding addresses). You can also add all these features to your website using the Google Maps APIs provided by Google. In this tutorial I will show you how to add some of these features to your site. I will be using the Google Maps Javascript API v3 (the newest version).

What are we going to build?

We’ll make a distance finder. We’ll add a Google map to our site, plot two points on it (the user will be able to choose the addresses for these points), compute the distance between them and show the quickest route between them.

You can see the demo of application here. Also, you can download the source code using this link.

Prerequisites

The first thing you need to do in order to use the API from Google is requesting an API key. You can do this here. It’s easy and free!

Creating the web form for getting the two addresses

We’ll create a simple html form for the user to write the two addresses. We’ll add two input boxes and a button to the form. When the user presses the “Show” button, the map with the two locations will be shown.

Here’s the code for this:

<table align="center" valign="center">
<tr>
   <td colspan="7" align="center"><b>Find the distance between two locations</b></td>
</tr>
<tr>
   &nbsp;
</tr>
<tr>
   <td>First address:</td>
   &nbsp;
   <input name="<span class=" type="text" />address1" id="address1" size="50"/>
   &nbsp;
   <td>Second address:</td>
   &nbsp;
   <input name="<span class=" type="text" />address2" id="address2" size="50"/>
</tr>
<tr>
   &nbsp;
</tr>
<tr>
   <td colspan="7" align="center"><input type="button" value="Show" onclick="initialize();"/></td>
</tr>
</table>

The ‘initialize’ JavaScript function will be called when pressing the button. The function will show the map. In the next section I’ll show you how.

We also need to add a div tag to our page, where the map will be shown:

<div id="map_canvas" style="width:70%; height:54%"></div>

We will also need two div tags for showing the distances we will compute:

<div style="width:100%; height:10%" id="distance_direct"></div>
<div style="width:100%; height:10%" id="distance_road"></div>

Showing the map

The first thing we need to do is to find the coordinates (latitude and longitude) for the two addresses. Luckily, Google Maps will help us! Here’s what we have to do:

We’ll use the geocoder object for this. First, we’ll have to create a new geocoder object.

geocoder = new google.maps.Geocoder();

After this, we’ll get the two address values from the form. Like this:

address1 = document.getElementById("address1").value;
address2 = document.getElementById("address2").value;

Then, we’ll use the following code to call the geocode method on the geocoder object. We’ll pass it the addresses one by one and save the results in the variables called location1 and location2 (these will hold the coordinates of the two addresses).

if (geocoder)
{
   geocoder.geocode( { 'address': address1}, function(results, status)
   {
      if (status == google.maps.GeocoderStatus.OK)
      {
         //location of first address (latitude + longitude)
         location1 = results[0].geometry.location;
      } else
      {
         alert("Geocode was not successful for the following reason: " + status);
      }
   });
   geocoder.geocode( { 'address': address2}, function(results, status)
   {
      if (status == google.maps.GeocoderStatus.OK)
      {
         //location of second address (latitude + longitude)
         location2 = results[0].geometry.location;
         // calling the showMap() function to create and show the map
         showMap();
      } else
      {
        alert("Geocode was not successful for the following reason: " + status);
      }
   });
}

You will notice that we’ve called the showMap() function when the coordinates for the second address are retrieved. This function will set the options for the map and show it.

We’ll now compute the coordinates for the center of the map. The center point will be between our two points.

latlng = new google.maps.LatLng((location1.lat()+location2.lat())/2,(location1.lng()+location2.lng())/2);

Next, we’ll show the map. We have to create a new map object and pass it some parameters (set using the mapOptions variable): the zoom level, the center and the type of the map.

var mapOptions =
{
   zoom: 1,
   center: latlng,
   mapTypeId: google.maps.MapTypeId.HYBRID
};

map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions);

The next thing we’ll do is to show the quickest route between our locations. We’ll use a DirectionsService object from google maps for this. Here’s how the code looks:

directionsService = new google.maps.DirectionsService();
directionsDisplay = new google.maps.DirectionsRenderer(
{
   suppressMarkers: true,
   suppressInfoWindows: true
});
directionsDisplay.setMap(map);
var request = {
   origin:location1,
   destination:location2,
   travelMode: google.maps.DirectionsTravelMode.DRIVING
};
directionsService.route(request, function(response, status)
{
   if (status == google.maps.DirectionsStatus.OK)
   {
      directionsDisplay.setDirections(response);
      distance = "The distance between the two points on the chosen route is: "+response.routes[0].legs[0].distance.text;
      distance += "The aproximative driving time is: "+response.routes[0].legs[0].duration.text;
      document.getElementById("distance_road").innerHTML = distance;
   }
});

We’ve first created the objects we need. We then set some options for displaying the route, we’ve chosen not to show markers and info boxes (we’ll create our own ones);

suppressMarkers: true,
suppressInfoWindows: true

We’ve created a request object and set the origin and destination for the route and also the travel mode:

var request = {
   origin:location1,
   destination:location2,
   travelMode: google.maps.DirectionsTravelMode.DRIVING
};

We’ve then called the route function and obtained a response from the server. Using this response we’ve plotted the route on the map and written some info (the total distance and aproximative driving time) in one of the divs we’ve created:

directionsDisplay.setDirections(response);
distance = "The distance between the two points on the chosen route is: "+response.routes[0].legs[0].distance.text;
distance += "The aproximative driving time is: "+response.routes[0].legs[0].duration.text;
document.getElementById("distance_road").innerHTML = distance;

We’ll also show a line between our points and compute the distance between them (the distance on a straight line, in kilometers). To show a line we’ll use a Polyline object from google maps and set some options for it (the map it belongs to, the path, the width, the opacity and the color):

var line = new google.maps.Polyline({
   map: map,
   path: [location1, location2],
   strokeWeight: 7,
   strokeOpacity: 0.8,
   strokeColor: "#FFAA00"
});

We’ll now compute the distance between two points using their coordinates and show the result inside the other div tag we’ve created.

var R = 6371;
var dLat = toRad(location2.lat()-location1.lat());
var dLon = toRad(location2.lng()-location1.lng());
var dLat1 = toRad(location1.lat());
var dLat2 = toRad(location2.lat());
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
        Math.cos(dLat1) * Math.cos(dLat1) *
        Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = R * c;

document.getElementById("distance_direct").innerHTML = "The distance between the two points (in a straight line) is: "+d;

The last thing we’ll do is show a marker and an info window for each location. We’ll create two marker objects (the options we’ll set are: the map it belongs to, the coordinates and a title):

var marker1 = new google.maps.Marker({
   map: map,
   position: location1,
   title: "First location"
});

var marker2 = new google.maps.Marker({
   map: map,
   position: location2,
   title: "Second location"
});

Next, we’ll create variables to hold the texts to print in the info windows, create two info window objects (we’ll add the texts to them using the content option) and we’ll add two event listeners which will show the appropriate info window when the user clicks on the markers:

// create the text to be shown in the infowindows

var text1 = '
<div id="content">'+</div>
  '<h1 id="firstHeading">First location'+
  '<div id="bodyContent">'+
  '<p>Coordinates: '+location1+'</p>'+
  '<p>Address: '+address1+'</p>'+
  '</div>'+
  '</div>';

var text2 = '
<div id="content">'+</div>
  '<h1 id="firstHeading">Second location'+
  '<div id="bodyContent">'+
  '<p>Coordinates: '+location2+'</p>'+
  '<p>Address: '+address2+'</p>'+
  '</div>'+
  '</div>';

// create info boxes for the two markers
var infowindow1 = new google.maps.InfoWindow({
   content: text1
});
var infowindow2 = new google.maps.InfoWindow({
   content: text2
});

// add action events so the info windows will be shown when the marker is clicked
google.maps.event.addListener(marker1, 'click', function() {
   infowindow1.open(map,marker1);
});

google.maps.event.addListener(marker2, 'click', function() {
   infowindow2.open(map,marker2);
});

And we’re done! We now have a distance finder! Let me know if you have any questions!

Irina Borozan

Irina is a software developer from Bucharest, Romania. She enjoys working on various programming projects. She likes spending her spare time reading, hiking, travelling, skating or playing tennis. She also blogs a bit. You can find her online in her home on the internet and on twitter.

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Comments

  1. Alex says

    A great tool and tutorial, but where do I put my google API key? I don’t want to use up your quota!
    many thanks.

  2. Alex says

    Hi, this is a great tutorial and tool, but was wondering where do I put my google API key? I don’t want to use up your quota! :)

  3. Hamed says

    good job
    it is my question too”Hi, your tutorial is excellent but may i know how do i calculate the distance for 5 markers ??”

    thanks for sharing

  4. Kangtp says

    Hi, your tutorial is excellent but may i know how do i calculate the distance for 5 markers ??

  5. Bhavit says

    Hi,
    Thanks a lot for detailed tutorial. I was wondering If we can add hundreds of addresses or load result from excel/google spreadsheet (colum A is source and Column B is destination). It will be much appreciated if you can propose any solution.
    Thanks

  6. Lina says

    Hi, Thanks for your detailed explanation. I think you can help me. I am trying to draw a path based on a set of geo coordinates on my own map(not google maps) but I do not know how to create the path. Does google maps API support a function in which the returning result is a path(probably a set of lines)?

  7. cham2748 says

    i want to do same in visual basic application..please help me..i almost done with my app,but i cant do the exact thing in vb form..(im using vb 6) your help highly appreciated,thank you.

  8. Ankit says

    I am trying to convert it into Miles but :( not getting any success plz anyone can help me out………

  9. Bob says

    Very nice, thanks for all the hard work. One question though. The “straight line distance” is always greater than the “chosen route” which seems to agree with Google Maps. How can the straight line distance be greater than a route that must follow roads and streets?

  10. Liaqat Ali says

    Hello,
    nice tutorial, and i implement it very easily in my site.
    I want 1 thing more, the distance between the cities are showing in English How can I show the distance in other languages. i need Portuguese Language.
    thanks in advace

  11. Shaheryar says

    hiya,

    I would say its wonderful tutorial I have came across, I was just wondering if you can give an idea how can I create random markers between start and end location. lets say start and end location is same and I want to put three way points randomly in such a way that I can control the duration of distance between start and end point. like if way points are placed randomly and I ckeck if distance is greater than 1 hour then reduce distance to one hour.

    I would really appreciate if you can propose a solution

    • says

      Hi

      Yes, this could be done. You will have to add one more point on the route. Actually 3 points, and recompute the route via each of those and check the results :)

  12. Dave says

    Great tutorial thank you very much, I was wondering if there was a way of adding the fuel cost into it? Cant seem to find anything on the api!

    • says

      Hi

      There’s nothing like that in the api, but you could add something. You get the distance from the api, use a variable for the fuel cost and compute the result :)

  13. says

    Hi Irina,

    Great document very helpful for me and my project but i have a question:

    Is it possible to work out the distance im miles rather than KM?
    Is it possible to work out the round distance ie there and back? i am creating a mileage tracking system that would track the distance for the full journey.

  14. Kalpesh says

    First Thanks a lot for such a superb helpful stuff.
    now here I need something more,
    like:”I want to offer the choose the way from Suggested routes(not by default shortest one)”.
    so its possible,please if it possible help me,
    thanks in advance….

    Thanks & Regards,
    Kalpesh

  15. Barto says

    Hello. I was playing on your aplication and I found a small error. When You click show the aplication displays the map properly. But when You do it again (doesn’t matter if you change the location) map shows whole world and the javascript error occurs. I was trying to fix it. If you change the default zoom parameter from 1 to 2 it works perfect. I don’t know why exacly but it does.

    Thanks alot for this tutorial. It was very helpful for me.

  16. says

    Hi Irina,

    Thanx a million for writing such an wonderful Google map tutorial! It is very good and well explained tutorial. Looking forward to read the second part. :)

    One thing I just can’t understand. Where to use the KEY which Google gives in the sign-up page? (I’m just a starter! :) )

  17. pove says

    Great tuto! Thanks! For Spanish people, try to find the rou from “Vete” to “Cagar”, it exists!

    ;-)

  18. Ryan says

    Hi Irina

    What an awesome tutorial thank you. Pehaps you can point me in the right direction:

    When a user starts typing in an address i would like it to automatically dropdown a suggested list of addresses. The same as it works for google map directions.

    If you can point me in the right direction It would be greatly appreciated.

    thanks
    Ryan

    • says

      Hello

      You would need to use some code for that auto-complete. There are loads of libraries (in javascript, jquery) available. Here’s an example:

      The library you choose to use depends on the programming language your app is written in and on the location of the data you want to show in the drop down.

      I hope this helps!

  19. Ryan says

    Hi Irina

    Do you know how i can get the google formatted address? Basically take the address entered and get the address back from google formatted correctly?

    Thanks in advance
    Ryan

    • says

      Hello

      That’s a really good idea! I haven’t thought of doing this before, but I will definitely look into it. I don’t know if there are any converters available though. You might need to write your own.

      I’ll let you know if I find anything useful!

  20. bago says

    very nice and very usable!!!
    a little hint: why don’t u convert the distance in a more useful way? i.e. in km

  21. says

    Hey. Great tutorial. I have always used google maps. Its interesting to see that there is lot more to it.

  22. daniele says

    i had to do this time ago for a website.
    don’t store the address, but use the lat and the long instead

    first of all i looped a php page that reads the addresses from the db, find lat and long via google geolocation and then store it into the db. starting from this moment you can always geolocate the point in the google maps reading its coordinates

  23. Omer Rosenbaum says

    Hi Irina!
    Great stuff you made there. I want to continue developing it and combine it with MySql.
    What I am trying to do is to get the 2 addresses into a DB. So far I haven’t had much success. Could you or anyone else can try to prepare such thing?

    • says

      That’s a good idea! I am probably going to write another tutorial on google maps and I could also add this to it.

      In the meantime, if you need some help with what you’ve tried so far, send me a message or something and I could help you.

  24. says

    Irina, nice tutorial I have done something similar on my site but I just outline the locations of where I have previously worked on my resume page. this helps potential people see the general area I work in.

    Shawn,

  25. emil says

    Multumesc pentru tutorial. Daca se poate traseu si cu ruta din 1, 2 puncte de trecere.
    Emil

    • says

      Bună idee :)

      It’s not very difficult to add more points on a route as you said, you just have to multiply to code for the textboxes and markers :)

  26. Matt says

    Nice tutorial! One question: why do you set the zoom level at 1? Wouldn’t it be better to make the zoom level high enough to show just the area with the two points defined by the user?

  27. Frank Bailey says

    Hi Irina, this is a great tutorial, thanks a ton! I’d just like to know if you might be able to provide a quick example of how we might be able to allow the user to click a point on the map to use as either the destination or origin, rather than entering and then geocoding the address?

    • says

      Hey, good idea! You’ll see something similar to this in the second part of the tutorial, which will be posted in a couple of days ;) I’m glad you enjoyed this one!

  28. says

    Hi!
    Very nice article, a small digression, you don’t need an API key if you’re using Googla Maps API v3. (You also didn’t use an API key in example provided with post.)
    Regards