23 - Finding the areas enclosing a feature

( //find the node named Uluṟu. Save it in a named set called "summit" node["name:pjt"="Uluṟu"]->.summit; //for the node(s) in the named set called "summit" find the areas they are in //save the results in another named set called "someArea" .summit is_in ->.someArea; //TRYME 2 try commenting out these two lines and looking in the //"Data" tab to see just the area data way(pivot.someArea); >; ); out body;

Sometimes we want to find the area that encloses some features of interest. For example, finding the administrative area for a firestation. Or the park that contains a play area.

This query demonstrates how to find the area that encloses a point using the is_in statement.

The is_in statement allows us to find areas based on some previously found nodes, ways or relations..

The first part of our query finds the area that contains the summit of Uluṟu:

node["name:pjt"="Uluṟu"]->.summit; .summit is_in ->.someArea;

A named result set (summit) is used here to make things clearer. We first store the node(s) we found in a variable called summit.

Then we use is_in to find which areas contain those elements. This will be ALL the areas that cover that point. Not just the boundary of Uluṟu, but also that of the Uluṟu-Kata Tjuṯa National Park, Petermann, the Macdonnell Region and so on all the way up to Australia.

is_in returns the full spatial coverage starting from one or more features.

The Overpass API will give us the tags associated with areas, but not their geometry.

If we want that, then we need to find the original ways or relations from which the area was created.

We do that by applying the pivot filter. This filter finds the corresponding OSM database feature for an area (or areas) in our result set.

In our example query we find the way that corresponds to the area surrounding the summit of Uluṟu like this:

way(pivot.someArea);

If we'd instead wanted to find a relation, then we would have used:

relation(pivot.someArea);

Source File	23-areas-from-features.osm
Authors	Leigh Dodds