check if a point exists in given area containing 4 vertices

Question

refering to http://www.weather.gov/directives/sym/pd01008006curr.pdf, page 8, we are given an area with four vertices in geographic coordinate system(lat and long system). I

Answer 1

The way to test whether or not a point is within an arbitrary polygon (any number of sides, concave allowed as well) is to choose a point that you know is OUTSIDE the polygon; if a line segment between the point you are testing and the point that is outside the polygon crosses an ODD number of the polygon segments, the point is within the polygon.