Overpass Tutorial
- 00 - The Beginning
- 01 - Finding nodes with a bounding box
- 02 - Outputting data about nodes
- 03 - Filtering nodes that have a tag
- 04 - Find nodes by matching tags and their values
- 05 - Find nodes by applying multiple filters
- 06 - Extracting multiple sets of nodes
- 07 - Calculating differences between results
- 08 - Generating JSON output
- 09 - Generating CSV output
- 10 - The default set
- 11 - Querying a set
- 12 - Searching within a radius using around
- 13 - Using around to filter against a set of results
- 14 - Searching by polygon
- 15 - Finding ways
- 16 - Ways and their nodes
- 17 - Ways and their tags
- 18 - Combining node and way queries
- 19 - Finding ways from their nodes
- 20 - Finding relations
- 21 - Type agnostic queries (nwr)
- 22 - Areas
- 23 - Finding the areas enclosing a feature
- 24 - Find the area derived from a feature
- 25 - Areas via Nominatim search
- 26 - Timeouts and endpoints
14 - Searching by polygon
OverpassQL supports searching for features within a polygon defined by a collection of points.
The poly filter accepts a single parameter. This must be a string value that
contains an even number of latitude and longitude pairs. Collectively these
coordinates should define a closed shape on the map.
This polygon is then used as the boundary for the query.
This query extracts nodes that can be found within a polygon that covers an area to the west of Uluášu.
There isn't a default bounding box defined in this query, as our area of
interest is fully described by the poly filter.
Note there's some quirks around syntax here which make poly slightly different to
around:
- the parameter MUST be provided as a quoted string.
- the coordinate values MUST be separated by spaces and not commas.
The syntax for the around filter is different.
Unfortunately, unlike around, the poly filter doesn't support querying based
on a polygon that was found by a previously extracted set of nodes.
So you can't, for example, extract the polygon describing a closed way stored in OpenStreetMap and then search within it. This feels like an oversight, but we'll see how to do this type of query later in the tutorial.
Tip: the more complex your polygon, the slower the search. Simplify the boundary to improve performance.
| Source File | 14-searching-by-polygon.osm |
| Authors |
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