Rectangle using CLLocationCoordinate2D

Question

I'd like to know whether I can create a rectangle using a top-left and bottom-right CLLocationCoordinate2D , and afterwards check whether a coordinate is part of this rectangle by checking (topLeftCoordinate.latitude < coordinate.latitude && bottomRightCoordinate.latitude > coordinate.latitude) && (topLeftCoordinate.longitude < coordinate.longitude && bottomRightCoordinate.longitude > coordinate.longitude) .

I thought a coordinate would represent a point on a sphere, and then this wouldn't work. But I get confused due to the 2D at the end of CLLocationCoordinate2D . Can someone clarify this?

Thanks :)

Answer 1

You will be able to create a MKPolygon from your coordinates and use this function to determine whether a coordinate is inside that polygon:

func isPoint(point: MKMapPoint, insidePolygon poly: MKPolygon) -> Bool {

    let polygonVerticies = poly.points()
    var isInsidePolygon = false

    for i in 0..<poly.pointCount {
        let vertex = polygonVerticies[i]
        let nextVertex = polygonVerticies[(i + 1) % poly.pointCount]

        // The vertices of the edge we are checking.
        let xp0 = vertex.x
        let yp0 = vertex.y
        let xp1 = nextVertex.x
        let yp1 = nextVertex.y

        if ((yp0 <= point.y) && (yp1 > point.y) || (yp1 <= point.y) && (yp0 > point.y))
        {
            // If so, get the point where it crosses that line. This is a simple solution
            // to a linear equation. Note that we can't get a division by zero here -
            // if yp1 == yp0 then the above if be false.
            let cross = (xp1 - xp0) * (point.y - yp0) / (yp1 - yp0) + xp0

            // Finally check if it crosses to the left of our test point. You could equally
            // do right and it should give the same result.
            if cross < point.x {
                isInsidePolygon = !isInsidePolygon
            }
        }
    }

    return isInsidePolygon
}