Resizing the Lines Drawing on Map on Zoom in and Zoom Out - ios

Question

I am drawing some custom lines using custom MKAnnotationView on MapView control. The drawing is between two defined points. The problem I am facing is that, when I zoom in or zoom out in an iPhone, the lines seems to zoom in and out too. This creates a weird effect as lines appear to be over different buildings and places once the user zoom in or out. How can I solve this problem?
Here is the code for custom AnnotationView:
#implementation JogAnnotationView
#synthesize points;
- (id)initWithAnnotation:(id <MKAnnotation>)annotation reuseIdentifier:(NSString *)reuseIdentifier pts:(NSMutableArray *)p
{
self = [super initWithAnnotation:annotation reuseIdentifier:reuseIdentifier];
if (self != nil)
{
CGRect cgRect =[[UIScreen mainScreen] bounds];
CGSize cgSize = cgRect.size;
CGRect frame = self.frame;
frame.size = CGSizeMake(cgSize.width/2, cgSize.height/2);
self.frame = frame;
self.backgroundColor = [UIColor clearColor];
self.centerOffset = CGPointMake(-5, -5);
self.points = p;
}
return self;
}
- (void)drawRect:(CGRect)rect
{
NSLog(#"%d",self.points.count);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextBeginPath (context);
CGContextSetLineWidth(context, 2.0);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGFloat components[] = {0.0, 0.0, 1.0, 1.0};
CGColorRef color = CGColorCreate(colorspace, components);
CGContextSetStrokeColorWithColor(context, color);
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
for (int i = 0; i < ([self.points count] - 1); i++)
{
JogPoint *startPoint = (JogPoint *) [self.points objectAtIndex:i];
JogPoint *endPoint = (JogPoint *) [self.points objectAtIndex:(i+1)];
CGContextMoveToPoint(context, startPoint.x ,startPoint.y);
CGContextAddLineToPoint(context,endPoint.x,endPoint.y);
}
}