Distance calculation based on multiple locations including starting/ finishing point

[nitapita]

I would like to calculate the total distance of driving beetween multiple locations (loop), including the distance (starting point (garage) - first location sarting point) and (last location finishig point - finishing point (garage)). Example: (Garage + D1) + (D1 + D2) + (D2 + E1) + (E1 + E2) + E2 + Garage)

 <?
$driver = 5;

     $result2 = mysql_query("SELECT * FROM test WHERE id='$driver' LIMIT 1") or die(mysql_error());
     while($row2 = mysql_fetch_array( $result2 )) {
         $lon=$row2['lon'];
         $lat=$row2['lat'];
    echo "$lon, $lat";
     }

   $result = mysql_query("SELECT * FROM test1 WHERE driver='$driver'") or die(mysql_error());  
    while($row = mysql_fetch_array( $result )) {

         $lon1=$row['lon1'];
         $lat1=$row['lat1'];
         $lon2=$row['lon2'];
         $lat2=$row['lat2'];

        //////////  distance between driver address and starting address    
        $distancecalc = (3958*3.1415926*sqrt(($lat-$lat1)*($lat-$lat1) + cos($lat/57.29578)*cos($lat1/57.29578)*($lon-$lon1)*($lon-$lon1))/180);
        //////////  distance between statring address and finishing address  - multiple adsresses
        $distancecalc1 = $distancecalc1 + (3958*3.1415926*sqrt(($lat2-$lat1)*($lat2-$lat1) + cos($lat2/57.29578)*cos($lat1/57.29578)*($lon2-$lon1)*($lon2-$lon1))/180);
        //////////  distance between finishing address and driver address
        $distancecalc2 = (3958*3.1415926*sqrt(($lat2-$lat)*($lat2-$lat) + cos($lat2/57.29578)*cos($lat/57.29578)*($lon2-$lon)*($lon2-$lon))/180);

        $distancetotal = $distancecalc + $distancecalc1 +$distancecalc2;

        echo "$distancecalc<br>
        $distancecalc1<br>
        $distancecalc2<br>";
    }
    echo "$distancetotal";
  ?>

I'm aware that code posted above doesnt't do what it meant to .. i just want to keep it clear.. there is some things i tried but no correct resoults.

I would appreciate some help on this one.

Thank you very much.

[nitapita]

Ok. I worked it out with help of mac_gyver (php freaks). All calculations are done as i wish. My code below:

<?
include "connectdb.php";
$driver = 5;
$datestamp = '2013/05/07';
$result2 = mysql_query("SELECT * FROM drivers WHERE id='$driver' LIMIT 1") or die(mysql_error());
while($row2 = mysql_fetch_array( $result2 )) {
$lon=$row2['lon'];
$lat=$row2['lat'];
}

$result = mysql_query("SELECT * FROM quotedb WHERE moveday='$datestamp' AND driver='$driver' AND cleared='Not Cleared' AND status='Done' ORDER BY moveday, timeday") or die(mysql_error());
$distance = 0; // accumulate the distance
$first_pass = true; // flag to detect the first row inside the loop
while($row = mysql_fetch_assoc( $result )) {
$lon2a=$lon2;
$lat2a=$lat2;
$lon1=$row['lon1'];
$lat1=$row['lat1'];
$lon2=$row['lon2'];
$lat2=$row['lat2'];
// calculate the distance from the Garage to the first point of the first row
if($first_pass){
$distance += (3958*3.1415926*sqrt(($lat-$lat1)*($lat-$lat1) + cos($lat/57.29578)*cos($lat1/57.29578)*($lon-$lon1)*($lon-$lon1))/180);
$first_pass = false;
}
// calculate the distance for each row (segment) in the route
$distance += (3958*3.1415926*sqrt(($lat2-$lat1)*($lat2-$lat1) + cos($lat2/57.29578)*cos($lat1/57.29578)*($lon2-$lon1)*($lon2-$lon1))/180);
if ( $lon2a == "" or $lat2a =="" ) {
} else {
// calculate the distance from the second point of the first row to the first point of the next row
$distance += (3958*3.1415926*sqrt(($lat2a-$lat1)*($lat2a-$lat1) + cos($lat2a/57.29578)*cos($lat1/57.29578)*($lon2a-$lon1)*($lon2a-$lon1))/180);
}
}
// calculate the distance from the second point of the last row to the Garage
$distance += (3958*3.1415926*sqrt(($lat2-$lat)*($lat2-$lat) + cos($lat2/57.29578)*cos($lat/57.29578)*($lon2-$lon)*($lon2-$lon))/180);
echo "$distance<br>
";
?>

Still think there is a place for improvement in the code. Will aplay Haversine method for calculations. Do you guys have some suggestion to improve this piece of code ... thx

[fretburner]

Hi nitapita,

There are a couple of things that you could do which I think would improve the readability of the code and make it easier to maintain.

1. Make the distance calculation into its own function:

function calculate_distance($lon1, $lat1, $lon2, $lat2) {
    return (3958 * 3.1415926 * sqrt(($lat2 - $lat1) * ($lat2 - $lat1) + cos($lat2 / 57.29578) * cos($lat1 / 57.29578) * ($lon2 - $lon1) * ($lon2 - $lon1)) / 180);
} 

This avoids repeating the code, and means you only need to make the change once if you change how the calculation is done (or if there's a bug).

2. You can simplify your while loop:

$previous_lon = $garage_lon;
$previous_lat = $garage_lat;
$distance = 0; // accumulate the distance

while($row = mysql_fetch_assoc( $result ))
{
    $lon1 = $row['lon1'];
    $lat1 = $row['lat1'];
    $lon2 = $row['lon2'];
    $lat2 = $row['lat2'];
    
    if ( $previous_lon && $previous_lat )
    {
        // calculate the distance from the second point of the first row to the first point of the next row 
        $distance += calculate_distance($lon1, $lat1, $previous_lon, $previous_lat);
    }
    
    // calculate the distance for each row (segment) in the route
    $distance += calculate_distance($lon1, $lat1, $lon2, $lat2);

    $previous_lon = $lon2;
    $previous_lat = $lat2;
}

// calculate the distance from the second point of the last row to the Garage
$distance += calculate_distance($garage_lon, $garage_lat, $lon2, $lat2); 

here, instead of checking if it's the first pass, you can set your previous latitude & longitude variables to the garage values before beginning the loop.

3. Instead of checking if variables are empty and then running some code in the else block:

if ( $lon2a == "" or $lat2a =="" ) { 
} else {
    // calculate the distance from the second point of the first row to the first point of the next row 
} 

you can simplify it like this (php will return false if the variables are empty strings) and avoid the empty braces:

if ( $lon2a && $lat2a )
{
    // calculate the distance from the second point of the first row to the first point of the next row 
} 

4. In the code above, I've renamed several of the variables to make it clearer what they are - for example, $lon2a and $lat2a become $previous_lon, and $previous_lat.

[nitapita]

Thanks a lot fretburner ! Good lesson. Applied the changes. It works.

[nitapita]

<?
include "connectdb.php";
$driver = 5;
$datestamp = '2013/05/07';
$result2 = mysql_query("SELECT * FROM drivers WHERE id='$driver' LIMIT 1") or die(mysql_error());
while($row2 = mysql_fetch_array( $result2 )) {
         $garage_lon=$row2['lon'];
         $garage_lat=$row2['lat'];
     }

$result = mysql_query("SELECT * FROM quotedb WHERE moveday='$datestamp' AND driver='$driver' AND cleared='Not Cleared' AND status='Done' ORDER BY moveday, timeday") or die(mysql_error());  
    
    function calculate_distance($lon1, $lat1, $lon2, $lat2) {
    return (3958 * 3.1415926 * sqrt(($lat2 - $lat1) * ($lat2 - $lat1) + cos($lat2 / 57.29578) * cos($lat1 / 57.29578) * ($lon2 - $lon1) * ($lon2 - $lon1)) / 180);}  
    
$previous_lon = $garage_lon;
$previous_lat = $garage_lat;
$distance = 0; // accumulate the distance

while($row = mysql_fetch_assoc( $result ))
{
    $lon1 = $row['lon1'];
    $lat1 = $row['lat1'];
    $lon2 = $row['lon2'];
    $lat2 = $row['lat2'];
    if ( $previous_lon && $previous_lat )
    {
        // calculate the distance from the starting point garage to the first point of the first row 
        $distance += calculate_distance($lon1, $lat1, $previous_lon, $previous_lat);
    }
    // calculate the distance for each row (segment) in the route
    $distance += calculate_distance($lon1, $lat1, $lon2, $lat2);
    $previous_lon = $lon2;
    $previous_lat = $lat2;
}
// calculate the distance from the second point of the last row to the Garage
$distance += calculate_distance($garage_lon, $garage_lat, $lon2, $lat2);  
    $distance = round($distance,0);
echo "$distance<br>
";
  ?>