# Detecting if GPS coordinates fall within polygon of points?

I'm looking for a simple explanation on how to detect if GPS coordinates fall within a polygon of points.

I would prefer an explanations that can be done using paper and pencil and not programming language specific.

If I have a list of points (latitude and longitude in degrees) that makes up a polygon. How can I tell if a point falls withing that polygon.

The only data I have access to is the polygon points and the point to check. An example is: `41.21,-104.77`(point to check) then I have polygon points (`39.39 -101.69 + 48.8335,-106.2435 + 38.803,-109.5781 + 39.4413,-111.043 + 45.6336,-113.7162 + 48.8335,-106.2435`) I found a Java specific answer and an R specific answer but I am looking for a programming language agnostic answer. Something written in plain English/step by step.

• The only data I have access to is the polygon points and the point to check. An example is: `41.21,-104.77`(point to check) then I have polygon points (`39.39 -101.69 + 48.8335,-106.2435 + 38.803,-109.5781 + 39.4413,-111.043 + 45.6336,-113.7162 + 48.8335,-106.2435`) Is there a way to find it with just this info? it seems like the solution above I would need a list of all the points for boundaries... which I do not have. Thanks! – Tim May 8 '18 at 22:11