Finding Closest Driving Distance

Question

I have a series of functions used to calculate the closest driving distance from the target address to one of my several locations and for the most part it works well. It first gets my closest location as the crow flies, then uses that address to calculate the actual driving distance to the target address and this is where the problem is. Sometimes the as the crow flies distance is far closer to one location but closer to drive from another so how can I calculate the driving distance from the start and skip the as the crow flies calculation?

// Provides "as the crow flies" distance from my closest location to target address
function closestLocation($Address) {
    $values = locationFromAddress($Address);
    $center_lat = $values[0];
    $center_lng = $values[1];   
    // My locations
    $query = sprintf("SELECT ID, Address, (3959 * acos(cos(radians('%s')) * cos(radians(lat)) * cos(radians(lng) - radians('%s')) + sin(radians('%s')) * sin( radians(lat)))) AS Distance 
    FROM locations 
    WHERE Address > 0 AND lat <> 0 AND lng <> 0 
    ORDER BY Distance ASC
    LIMIT 1",
      $center_lat,
      $center_lng,
      $center_lat);
    $rowCat = DBConnect($query, "Select", "pchome_geoip");

    // Returns array of the location
    return $rowCat;
}

You can see that the query simply uses the latitude and longitude stored in the database to calculate it using the latitude and longitude of the target address provided by locationFromAddress() function:

function locationFromAddress($Address) {
    $Address = urlencode($Address);
    if ($Address) :
        $geocode = file_get_contents("http://maps.google.com/maps/api/geocode/json?address=$Address&sensor=false");
        $output = json_decode($geocode);
        $lat = $output->results[0]->geometry->location->lat;
        $long = $output->results[0]->geometry->location->lng;
        return array($lat,$long);
    else:
        return "";
  endif;
}

And then the details are used to calculate the driving distance using the Google API:

function compareDistance($unit,$inLatitude,$inLongitude,$outLatitude,$outLongitude) {
    $url = "http://maps.googleapis.com/maps/api/directions/json?origin=$inLatitude,$inLongitude&destination=$outLatitude,$outLongitude&sensor=false";

    // Retrieve the URL contents
    $c = curl_init();
    curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($c, CURLOPT_URL, $url);
    $jsonResponse = curl_exec($c);
    curl_close($c);

    $dataset = json_decode($jsonResponse);
    if(!$dataset)
        return 0;
    if(!isset($dataset->routes[0]->legs[0]->distance->value))
        return 0;
    $miles = ($dataset->routes[0]->legs[0]->distance->value * .00062);
    // Google API returns meters, multiplied by .00062 to get miles

    // Round up to nearest unit
    if ($unit == "K") :
        return ceil($miles * 1.609344);
    elseif ($unit == "N") :
        return ceil($miles * 0.8684);
    else :
        return ceil($miles);
    endif;
}

function getDrivingDistance($myAddress, $custAddress, $unit) {
    // 'M' is statute miles
    // 'K' is kilometers
    // 'N' is nautical miles
    // Get accurate latitude and longitude based on actual location
    $myValues = locationFromAddress($myAddress);
    $myLat = $myValues[0];
    $myLng = $myValues[1];  

    $custValues = locationFromAddress($custAddress);
    $custLat = $custValues[0];
    $custLng = $custValues[1];

    // Returns actual driving distance
    return compareDistance($unit,$myLat,$myLng,$custLat,$custLng);
}

Also, is there an API parameter for closest rather than fastest route?

Answer 1

I reworked this function and entirely eliminated closestLocation() and another function so it does simplify things a bit. I'll need to rearranged a few of the other areas of where this is being called but it does seem to be pulling out a valid driving distance although sometimes it's the fastest, not the closest. Is there a switch for the Google API for closest?

function getDrivingDistance($Address,$unit="M") {
    if ($Address) :
        $values = locationFromAddress($Address);
        $inLatitude = $values[0];
        $inLongitude = $values[1];  

        // Fetch all of my locations
        $sqlLocation = "SELECT ID, Address, lat, lng 
                        FROM locations";
        $rowLocation = DBConnect($sqlLocation, "Multiple", "pchome_geoip");

        // Create array of driving distances based on latidude and longitude
        foreach ($rowLocation as $key) :
            $outLatitude = $key['lat'];
            $outLongitude = $key['lng'];
            $output[] = compareDistance($inLatitude,$inLongitude,$outLatitude,$outLongitude,$unit);
        endforeach;

        //sort($output, SORT_NUMERIC);
        if (array_sum($output) > 0) :
            return min(array_diff($output,array(0)));
        else :
            return 0;
        endif;
    endif;
}