Point in Polygon for a map projection
Built for students learning it for a class or exam. See the concept move instead of memorizing formulas — and check your homework intuition. Simulate a map projection live below — adjust the inputs and watch it respond, right in your browser.
Controls
Is a point inside a shape? The ray-casting algorithm shoots a ray from the point in any direction and counts how many polygon edges it crosses: an odd number means inside, an even number means outside. It is the math behind geofencing — triggering an alert when a phone or vehicle enters or leaves a region — and behind hit-testing in graphics. Drag the point, or click anywhere to move it there.
Data Inspector
Governing equation
Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.
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Frequently asked questions
- Is this good for students?
- Yes — this version of "Point in Polygon for a map projection" is framed for students learning it for a class or exam. See the concept move instead of memorizing formulas — and check your homework intuition.
- Do I need to install anything?
- No. It runs in any modern browser, free, with no account required.