Posts Tagged ‘Google Maps API’

Google Maps API part 2: Retrieving Postcodes from your database

googlemaps part2

OK, this is a simple way to get your postcode/ address location returned and displayed via the Google Maps API on your own website. I’ll cover the ‘nearest store locator’ scenario in another post where you want places with a certain radius of an inputted postcode/ town returned.

First of all we need to retrieve our results which should already be stored with a geocoded result using the previous tutorial here. remember that in order for this to work you need an API key from google – again check the previous tutorial for more info on this.

We’re going to need to pass the geocoded values retrieved from the database into javascript and there are a few ways of doing this. This is really the hardest part and the only work you really need to do to display your result on a map as the Google maps API does the rest of the work for you. So we can either do this via something like an AJAX request whereby you build your returned data into an XML file and then use javascript to read that. Or you can write your php inline inside the javascript, which is messy for multiple results but in the singular it should be fine.

First lets start with the chunk of javascript on the page that will display our map etc… This method just calls up a map from the API and then zooms, centers and adds a marker to a specified co-ordinate. This singular display is useful if you want to, for instance, display the location of a result in a popup/ overlay.

// your API key here.



To see the map just add in a HTML element and set an onload event assigned to your body tag as thus

So now we just need to pass in our result from the database. Starting with passing it inline to javascript variable we can do the following, first connect and get your results from your database, very basically as below.

 LIMIT 1");

// assign the results to variables something like:
while ($row = @mysql_fetch_assoc($result)){
$lat = $row['lat'];
$lng = $row['lng'];
}
?>

Ok, so in javascript we can then put in our php values:


// declare variable to store co-ordinates - fetch these from your database

// var coords = new GLatLng(51, -1);
// or you can do this:
// var coords = new GLatLng(, );

So all together the php page will look something like this:

 LIMIT 1");

// assign the results to variables something like:
while ($row = @mysql_fetch_assoc($result)){
$lat = $row['lat'];
$lng = $row['lng'];
}
?>



For retrieving the results via an XML file instead I’ll cover that in part 3 as its much more applicable there.

Google Maps API part 1: Accurate Geocoding for UK Postcodes

googleMaps

Recently I had to build a system that would take an address, pass it to google and return latitude and longitude values. The result is then stored for later use and display on Google maps.

However, firstly I found that the default XML geocoding service provided by Google that allows you to do bulk geocoding on a data source and the geocoding provided by their maps API/ AJAX library (GClientGeocoder) had huge differences in results. Most postal codes passed to googles XML geocoding service were miles out or just not recognised. Yet when using the same postcode in the maps API when calculated on the fly the results were more or less spot on.

You can take a look at a tutorial for using Googles XML geocoder service, PHP and MySQL here. They suggest that this way is good if you don’t want to repeatedly geocode the same address again and again and if you want to do bulk geocoding.

Which would be nice, if it was actually accurate! But this still leaves me with having to do bulk uploads or geocoding and get accurate results to build, for instance, a store locator around the data.

The solution is simple, we can utilise the Google maps API to do the geocoding for us on the fly and store the result passed back using some simple AJAX to send the data to PHP/ MySQL. While I geocode my records at the time of their entry, in the example below, you could just as easily use this to create some sort of bulk update. Check out my tutorial here about using AJAX to pass form data to PHP if you’re new to this.

Firstly you will need to signup to get a couple of free API keys from google, you don’t require much to get them and they’ll work just fine for a localhost.

Maps API key: http://www.google.com/apis/maps/signup.html
AJAX Search API key: http://code.google.com/apis/ajaxsearch/signup.html

OK so now we create a HTML page, form.htm, this will call in the Javascript libraries and do the geocoding work.



We also build a function that creates an XML object in the DOM to store the data, which will then get passed to the PHP page. This works in exactly the same way as my tutorial here.


This chunk of code above is what utilises the google maps keys, to pass the data to google, geocode it and return the record and I've written this inside of a function that gets called on the form submission, which in turn then uses the previously declared XML creation function.

The final stage of this HTML page is of course the form which sends the data and a span tag that displays the results if successful.


Address Line 1:
Address Line 2:
Address Line 3:
Town:
Postcode:
 

Server-Response:

This then just leaves us the PHP page (post.php) that will then post the results, again nothing too disimilar to my previous tutorials on this. This is the bit where you would pass in the $_POST parameters and store them using MySQL etc... or save them to a text file.


And there we have it, accurate geocoding from google that can be used as a service when data is entered, or you could use this same method by passing in XML created from your database and iterating over this passing each result to the API and returning a value.

Now you can build a store locator or whatever that actually returns accurate results, also you can then use this to integrate your database better with the full Google maps API - showing maps, placing markers on maps etc..