Using Google Maps API to determine the driving distance between two locations

Is this just to be used in a PHP script?  Will the server have the to and from addresses then?  Those won't come from input at all?

What is the xml or json needed for?  If it is just the miles then what else would go in the xml or json?  It seems like you just have one piece of info. :)

Getting this clarified will help to know the best solution.  Although Google doesn't have an official way to get the info we still may need to be able to do it just from PHP.  However if you are getting the addresses from the client then an AJAX method or form submission could be used to get the miles to your PHP script.  The API would be used but then a form or AJAX script would send it to the server.

Let me know if you have a question about this.

bol

@bol: I know this is not a simple question.  Thanks for trying to help.

I don't have a problem getting the address from the clients; that is simple <form> input.  I don't have a problem geocoding the address (turns the address into a latitude/longitude pair).  You can call the Google geocoder or the Yahoo geocoder and get the latitude/longitude pairs.  The terms of service for either lets you geocode thousands of addresses each day, and that's plenty for my needs.

For example, if you want to get the geocoded address for zip code 20016, you can use the script in the code snippet.  Google returns a string of comma-separated values.  There is also a way to get back XML, but for geocoding, the CSV is simple to use.  You can also buy pre-coded data.  It comes from the US Census and other sources.

It's easy to compute the distance between two geocoded addresses, but the computation only gives the distance "as the crow flies."

So far, so good.

Now if I knew the turn-by-turn driving directions, and I geocoded each turn, I could incrementally compute the driving distance by adding together all the little distances between each turn.  This would be much closer to the odometer mileage.  It wouldn't account for wiggly roads, but that's OK.  This _may_ be how Google determines the driving distance.

But I don't really need that level of detail, I just need the total driving distance - in one, easy to access, number.  

If you go to this URL:
http://maps.google.com/maps?f=d&hl=en&geocode=&saddr=20016&daddr=15222&ie=UTF8&z=9&pw=2

You can see that Google computes the travel distance to be 237 miles.

What I am looking for is a way to extract that value -- 237 miles -- in a way that does not violate the terms of service.  I have looked at the source information on that page and I can write a script to parse the HTML.  But that's clearly not the "best" answer.

What I am looking for is a formal interface to Google, Yahoo or some other map service that can give me a CSV string or XML string that contains the overall driving distance information.

Does that clarify what I'm trying to find?

Thanks, Ray

$zip = '20016';
$url = "http://maps.google.com/maps/geo?q=" . $zip . "&output=csv&key=[your API key]";
 
if ($fp = fopen($url, 'r')) {
	$buf	= '';
	while (!feof($fp)) {
		$buf .= fgets($fp);
	}
	fclose($fp);
} else { die("Google maps/geo failed for $zip"); }
 
echo $zip . ': ' . $buf . "\n";
$x = explode(',', $buf);
var_dump($x);
 
// $x contains this:
// $x[0] = 200 if successful
// $x[1] = 5, an indicator of precision in the geolocation process
// $x[2] = latitude
// $x[3] = longitude
                                              

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Ray,

Yes that info helps and cleared things up. I am familiar with the geocoding option but don't see that it is needed for what you are trying to do here.  Now I think I know why you mentioned JSON but with just one value we should not need it and the API doesn't send it as JSON like the geocoding process does.

I am sorry if it seems like this will be a bit of a run around, especially after the first question on this, but if you are getting the to and from address from input then it is best to just use the API, have Javascript get the info, and then pass it to the server. We already have the first 2 done in the script I provided. The key for the last is will the page be submitted or refreshed (i.e. a form sent) or do you want the info to go to the server without reloading the page (i.e. using AJAX)?

I will be happy to provide details on either method and help you put it in your page. It would help to know what your form looks like if you need help with that part. If you also want to make sure the value doesn't have html or can't use meters then let me know. Removing the html or converting meters to miles is not hard.

Thanks again for that info. Hopefully this last little bit will do it.

bol

bol, thanks.  In the code snippet is a sample of code that will isolate the driving distance.  I run that code on my server and it prints the answer.  It seems pretty reliable.  There are some local functions, but I'm sure you can figure them out if you read over the code.

It gives me back this output:
From 20016 to 15222 is 237 mi  about 4 hours 5 mins

What I'm looking for is a formal, Google-supported interface that will give me back the same information as I get in the $answer variable.

In the alternative, it could be an interface to Yahoo or any other mapping service.

That's really all I need.  

Best, Ray

// GET THE ZIP CODES (MAYBE FROM FORM INPUT)
$zip_home	= '20016'; 
$zip_away	= '15222'
 
// GET THE PRINTABLE DRIVING DIRECTIONS PAGE FROM GOOGLE
$google_url	= "http://maps.google.com/maps?f=d&hl=en&saddr=" . $zip_home . "&daddr=" . $zip_away . "&ie=UTF8&z=9&pw=2";
$google_html	= my_curl($google_url);
 
// TRUNCATE HEAD OF GOOGLE HTML STRING UP TO THE TIME AND DISTANCE TAG
$pointer	= strpos($google_html, "timedist ul");
if ($pointer === FALSE) { die("No timedist ul"); }
$google_html	= substr($google_html, $pointer, strlen($google_html));
 
// TRUNCATE TAIL OF GOOGLE HTML
$pointer	= strpos($google_html, "</td>");
$google_html	= substr($google_html, 0, $pointer);
 
// TIDY UP IN CASE GOOGLE EVER GOES TO STRICT
$google_html	= str_replace('"', '', $google_html);
 
// ISOLATE THE STRING WE WANT
$x = explode('<div class=pw>', $google_html);
$answer = trim(strip_tags($x[1]));
$answer	= str_replace('&#160;', ' ', $answer);
 
echo "From $zip_home to $zip_away is $answer \n";
                                              

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Thanks, Experts. I think the answer has to be a custom application.  No point in spending any more EE time on this one.  Best to all, ~Ray

Time to put this thing out of its misery.  Best, ~Ray

B-)) Interesting project and discussion! Thx for the points.

Your welcome!  I am glad I could help a bit.  Hopefully it wasn't painful.  ;)  It definitely has been interesting.

Thanks for the fun question, the grade and the points.

bol

Hi Ray,

Did you manage to do that in the end? Did you resolve the problem?
My question is similar:
http://www.experts-exchange.com/Web_Development/Web_Languages-Standards/PHP/Q_23954105.html

-------------

What im trying to do is, if i know:
1) Point A (in Lat Long)
2) Point B (in Lat Long)

I want to:
1) Calculate the distance using roads in KM
2) Offer driving directions
3)  Display the average time to get location by car / walking
4)  Use the GOOGLE Static Maps API to create the graphic using the markers to delineate the path that the Google Maps API has used to create the route. (so retrieve the lat long of the waypoints so i can use them in google static maps api)

All of this needs to be done on the server in PHP and presented as variables for output in HTML - i can run the php variables in the page but not javascript so everything must be processed server side.

Hi, I understand the question, believe me.  I have not solved the issue of driving distance, but I haven't got it as a business problem any more - I just decided the effort was going to yield only marginal improvement for my particular app, and I did not want to run afoul of the Google TOS, so I shelved it.  Your issue appears to be different and it may be a more central part of your app.

Since I posted that query last July, Google Maps has added many new features.  Such a thing may have come available since then.  But I haven't looked lately.

In any case, Good Luck! ~Ray

I think for me its a question of offering the most accurate advice for the end user - I know i can do the "as the crow flies" calculation and present it as --aprox but i would rather be realistic. Also, i need to be able to get those damn waypoints to create the static image using the Google Maps Static API.

Care to enlighten me on those Google TOS? Is it wise building the app using their mapping service?
All i know is that they limit it to 15K requests a day, which i wont be hitting (but maybe later)

thanks Ray

Sorry, I'm not really qualified to offer advice on the Google TOS - I just made evaluations for my own case.  You should consult a lawyer with IP experience for a qualified opinion.

In my case, I use both the Google geocoder and the Google maps service together.  So far the results have been fine.  I depend on Javascript in the browser.  And I make the assumption that the driving distance will be proportional to the "crow flies" distance.   So if I find that two points are close together geographically, I simply accept the "risk" that there is a river between them, with no bridge.  Since I am presenting a Google map, the client has to deal with the final choice of proximity and route.

FWIW, the XML from the Yahoo geocoder is somewhat simpler than the XML from the Google geocoder.

mmm... thanks for that... given me worry about the implication for the project though as im building something for mobiles.... So you cant display a map with javascript because of the limitation of mobiles, hence using the Google Static Maps API. But to get distances etc, i need to use the Google Maps API (somehow, maybe through AJAX) and then plot everything on a static map....

Thanks for the tips and i will keep ploughing the forums!

Yep, the Forum's the place to look.  Maybe look at Chrome support?  Anyway, good luck with the project. ~Ray