GPS coordinates in degrees to calculate distances

Question

On the iPhone, I get the user's location in decimal degrees, for example: latitude 39.470920 and longitude = -0.373192; That's point A.

I need to create a line with another GPS coordinate, also in decimal degrees, point B. Then, calculate the distance (perpendicular) between the line from A to B and another point C.

The problem is I get confused with the values in degrees. I would like to have the result in meters. What's the conversion needed? How will the final formula to compute this look like?

Answer 1

use - (CLLocationDistance)getDistanceFrom:(const CLLocation *)location

firstLongitude = 30.0;
firstLatitude = 30.0;

secondLongitude = 40.0;
secondLatitude = 40.0;

CLLocation *firstLoc = [[CLLocation alloc]initWithLatitude:firstLatitude longitude: firstLongitude];
CLLocation *secondLoc = [[CLLocation alloc]initWithLatitude:secondLatitude longitude: secondLongitude];

double distanceInMeters = [firstLoc getDistanceFrom: secondLoc];