# OSM (Multi)Polygon Statistics

This page shows several statistics related to multipolygons over time.

## Multipolygons created from relations

The number of multipolygons created from relations with
`type=multipolygon` or `type=boundary`.

## Multipolygons created from closed ways

The number of (multi)polygons created from closed ways. Tags are not
taken into account (except `area=no`), so this also includes
closed ways that are not actually polygons, such as roundabouts or so.

## Nodes in multipolygons

The total number of nodes in all multipolygons (created from relations or ways).

## Old style multipolygons

The number of multipolygon relations that have no tags (or only
unimportant ones like `created_by`) on the relation and have
their tags on the outer way(s) instead. This *old style* tagging
is deprecated.

The percentage of all multipolygon relations that have *old
style* tagging.

## Errors: Intersections

Multipolygon relations or ways with self-intersections of the way or ways involved. These are broken and need to be fixed. The number reported here is the number of crossing segments. Because you always have at least two segments involved in an intersection, the number of affected (multi)polygons is about half this size.

## Errors: Duplicate nodes

Multipolygon relations or ways with consecutive indentical nodes or multiple different nodes at the same location. These are usually fixed while post-processing the multipolygon, but it is still better to fix them in the data.

## Errors: Duplicate segments

Number of segments (a segment is a connection between two nodes) that appear multiple times in the border of a multipolygon relation or way. This is often, but not always wrong.

## Errors: Open rings

Multipolygon relation where the outer or inner border is not closed. This is always an error and needs to be fixed.

## Errors: Inner rings with same tags as outer rings

Some multipolygon relations have the same tags on outer and inner ways or the relation and inner ways. This is deprecated. Multipolygon tags should be on the relation only, outer ways are usually not tagged at all (unless they constitute an object in their own right), and inner rings either have no tags or their own tags if they constitute an object in their own right.

## Errors: Wrong role

Multipolygon member roles other than empty, `outer` or
`inner` or where the tagged role is not the correct one. This
reports the number of segments which have a wrong role, not the
number of ways or relations. That's why this number is so large.