calculate distance

Question

i am designing a recruitment database, and i need it to perform several tasks that all involve integrating a way of calculating distance:

1) calculate the distance t

Answer 1

Just a thought: If your clients and candidates live in a very limited area, I would use a rectangular map and enter x and y values for all cities in that area in a database.

Due to the pythagorean theorem, you can say:

distance² = (x-value client - x-value candidate)² + (y-value client - y-value candidate)²

Answer 2

First, isn't the radius actually the 'as crow flies' distance from the client to the candidates? Anyway...you will need to figure out an algorithm for computing what you need based on the distance between the points.

If you want the system to be stand-alone you will need to have the values for the coordinates (latitude, longitude) of the points. For this, you will probably need and internet connection and the use of a service like google maps to find the coordinates based on the addresses of the points. But once you store then in your db, you will not need an internet connection.

There is a formula for computing the distance between two points based on the coordinates, you will easily find it :)

Answer 3

The distance between 2 points could be calculated with the following formula :

6371*acos(cos(LatitudeA)*cos(LatitudeB)*cos(longitudeB-longitudeA)+sin(LatitudeA)*sin(latitudeB))

Of course it's a "crow flies" approximation in Km.

Wich can be translated to php by :

$longA     = 2.3458*(M_PI/180); // M_PI is a php constant
$latA     = 48.8608*(M_PI/180);
$longB     = 5.0356*(M_PI/180);
$latB     = 47.3225*(M_PI/180);

$subBA       = bcsub ($longB, $longA, 20);
$cosLatA     = cos($latA);
$cosLatB     = cos($latB);
$sinLatA     = sin($latA);
$sinLatB     = sin($latB);

$distance = 6371*acos($cosLatA*$cosLatB*cos($subBA)+$sinLatA*$sinLatB);
echo $distance ;

With that you could compute the distance between two points (people) and of course determine if a point is in a radius of an other.