Search for coordinates in a path - iphone

Question

I'm new in iOS iPhone development and I'm having some problems using maps.
I'm trying to find a way to create a path with lots of coordinates points (latitude, longitude) and then check if a specific coordinate point is inside this path. I've already looked for how to do this using Apple Maps and the new Google SDK, but with no success.
The complete problem is:
I have some coordinates (but not all) that represents the path that a vehicle pass by. I need to check if a specific coordinate is inside this vehicle path. For example: I have the coordinates X, Y and Z. If I create a path with this coordinates the complete path will have the coordinates X, Y, W and Z. With this path I can check for the coordinate W, that was not in the coordinates used to construct the path. It's something like creating a path between two points but telling the map to create a route using some checkpoints and after check if a random coordinate is inside this path.
There is a way to do something like this?

Answer 1

I guess for a simple solution you could use something like
(MKUserLocation *)userLocation;
CLLocation* X = [init from some coordinates];
CLLocation* Y = [init from some coordinates];
CLLocation* W = userLocation.location;
CLLocationDistance distToX = [X distanceFromLocation:W];
CLLocationDistance distToY = [Y distanceFromLocation:W];
and to detect how far W is from the line defined by X,Y, you can adjust the following code:
def pointLineDistance(p,v1,v2):
return (numpy.linalg.norm(p-v1)**2 * numpy.linalg.norm(v2-v1)**2 - (numpy.dot((v1-p),(v2-v1)))**2) / numpy.linalg.norm(v2-v1)**2
Sorry that I am using python & numpy here, just copy & pasted it, but thats the 2d / 3d generalized implementation of a distance between a point p (your W) and two other vectors v1,v2 (your X,Y).
Look up http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html
I don't know how it complies for spherical surface coordinates but it's ok for Eucledian space.
Cheers,
EL