SQLite Forum

Country-coding from Lat/Long, using GeoPoly and/or R-Tree
Apart from some member states of the USA, countries do not tend to be rectangular. They may also consist of several disjunct areas aka overseas territories.

The topological Definition of "inside" and "outside" is the parity of the count of intersections with the outline along an arbitrary path between the point of interest and a point whose inside/outside property is known.

e.g. draw a straight line from the POI to the (center of) capital of the country. If the number of intersections is even (ideally zero for convex polygons), then the POI is "inside" the country. Intersecting at a tangent does not count.