# RFC Errata

#### RFC 7946, "The GeoJSON Format", August 2016

Source of RFC: geojson (art)
Errata ID: 5069

**Status: Reported
Type: Technical
Publication Format(s) : TEXT**

Reported By: Clark Archer

Date Reported: 2017-07-14

Section 3.1.6 says:

3.1.6. Polygon To specify a constraint specific to Polygons, it is useful to introduce the concept of a linear ring: o A linear ring is a closed LineString with four or more positions. o The first and last positions are equivalent, and they MUST contain identical values; their representation SHOULD also be identical. o A linear ring is the boundary of a surface or the boundary of a hole in a surface. o A linear ring MUST follow the right-hand rule with respect to the area it bounds, i.e., exterior rings are counterclockwise, and holes are clockwise. Note: the [GJ2008] specification did not discuss linear ring winding order. For backwards compatibility, parsers SHOULD NOT reject Polygons that do not follow the right-hand rule. Though a linear ring is not explicitly represented as a GeoJSON geometry type, it leads to a canonical formulation of the Polygon geometry type definition as follows: o For type "Polygon", the "coordinates" member MUST be an array of linear ring coordinate arrays. o For Polygons with more than one of these rings, the first MUST be the exterior ring, and any others MUST be interior rings. The exterior ring bounds the surface, and the interior rings (if present) bound holes within the surface.

It should say:

3.1.6. Polygon To specify a constraint specific to Polygons, it is useful to introduce the concept of a linear ring: o A linear ring is a closed LineString with four or more positions. o The first and last positions are equivalent, and they MUST contain identical values; their representation SHOULD also be identical. o A linear ring is the boundary of a surface or the boundary of a hole in a surface. o A linear ring MUST follow the right-hand rule with respect to the area it bounds, i.e., exterior rings are clockwise, and holes are counterclockwise. Note: the [GJ2008] specification did not discuss linear ring winding order. For backwards compatibility, parsers SHOULD NOT reject Polygons that do not follow the right-hand rule. Though a linear ring is not explicitly represented as a GeoJSON geometry type, it leads to a canonical formulation of the Polygon geometry type definition as follows: o For type "Polygon", the "coordinates" member MUST be an array of linear ring coordinate arrays. o For Polygons with more than one of these rings, the first MUST be the exterior ring, and any others MUST be interior rings. The exterior ring bounds the surface, and the interior rings (if present) bound holes within the surface.

Notes:

This is only for the bullet point describing the right-hand rule for linear rings. It seems like the clockwise/counterclockwise descriptions are the opposite of the right-hand rule. Walking an exterior ring in a counterclockwise direction would have the exterior of the ring to the right of the observer.