The right-hand rule error for geojson

example of geojson structure

By using on of many geojson tester on line, like or (this is especially cool cause you can see the geometry in a map) you can receive this message “Invalid GeoJSON Line 51: Polygons and MultiPolygons should follow the right-hand rule”.

To avoid this error put counterclockwise the list of points of external boundary: by hand, by code (like Python geojson-rewind) o by webpage mapster-right-hand-rule-fixer.

So what’s right-hand rule?

This rule state that in a valid geojson Polygon at least 4 points have to delimit a surface (they are 4 because the simplest shape is a triangle, and the first and the last points are identical) and they have to be sorted counterclockwise.


This rules come from the standard of geojson (

In the standard a LineStrings is the name used for a linear ring, that’s a closed curve that represents the boundary of a surface or the boundary of a
hole in a surface

At paragraph 3.1.6. the standard states that, for a Polygon,  a LineStrings “MUST follow the right-hand rule with respect to the area it bounds, i.e., exterior rings are counterclockwise, and holes are clockwise.”

A visual explanation is here:


So, next time you face the right-hand rule error remember the you have to rewind (sort countuterclockwise) the external boundary. And also that, instade of boundary you can find the word ring.

An finally: that this rule is needed to avoid errors in the surface computation.




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