The Future of Areas/Areas on Ways

From OpenStreetMap Wiki
Jump to: navigation, search

Having areas made up from ways would basically look like today's multipolygon relations:

<area id="1">
  <ring role="outer"> (or just <outer>)
    <way ref="1" />
    <way ref="2" />
    <way ref="3" />
  </ring>
  <ring role="inner">
    <way ref="4" />
    <way ref="5" />
  </ring>
</area>

Advantages

This kind of area can easily accomodate very large polygons, and can also allow the re-use of its constituent parts by other aras.

Disadvantages

A way-based area type creates extra overhead when mapping small areas, like a rectangular building:

today with area on ways
<way id="1">
  <node ref="1" />
  <node ref="2" />
  <node ref="3" />
  <node ref="4" />
  <node ref="1" />
  <tag k="building" v="yes" />
</way>
<area id="1">
  <outer>
    <way ref="1" />
  </outer>
  <tag k="building" v="yes" />
</area>
<way id="1">
  <node ref="1" />
  <node ref="2" />
  <node ref="3" />
  <node ref="4" />
  <node ref="1" />
</way>

Like current multipolygon relations, if the end nodes for one of the multipolygon's ways are changed but the next way in the sequence is not edited, the continuity of the ring is broken. This kind of 'break' is not necessarily obvious to editors who are focusing on a way that has been 'recycled'. (E.g. the editor is editing a highway and doesn't realize that the highway represents part of a county border, but only if the highway way's end node matches the node of a river that crosses it.)

Variations