Nearest Join

Options

Left geometry column

Select the geometry column from the left (top) input table to join on.

Right geometry column

Select the geometry column from the right (bottom) input table to join on.

Join mode

The join mode determines of which input table the rows should be retained.

Available options:

• Inner: Retains only matching rows from both input tables.
• Left: Retains all rows form the left and only matching rows from the right input tables.
• Right: Retains all rows form the right and only matching rows from the left input tables.

Maximum distance

Maximum distance within which to query for nearest geometry. Must be greater than 0

CRS for distance calculation

Enter the Coordinate reference system (CRS) to use. The input field supports the following types:

• An authority string (i.e. 'epsg:4326')
• An EPSG code (i.e. 4326)
• CRS WKT string

Common EPSG codes that can be universally used for mapping coordinates everywhere in the world are:

• epsg:4326 (WGS 84, Unit: degree): Latitude/longitude coordinate system based on the Earth's center of mass; Used by the Global Positioning System among others. This is also the default projection that the geospatial nodes use if not otherwise specified.
• epsg:3857 (Unit: meter): Web Mercator projection used by many web-based mapping tools, including Google Maps and OpenStreetMap.

There are EPSG codes for specific regions that provide a higher accuracy in the corresponding regions:

• North America:
  • epsg:4269 (NAD83, Unit: degree)
  • epsg:26918 (NAD83 18N, Unit: meter)
• China
  • epsg:4490 (CGCS2000, Unit: degree)
  • epsg:4479 (CGCS2000, Unit: meter)

For a selection of projections that preserve different properties see this Wikipedia article. Once you have found the appropriate projection name or coordinate reference system you can search for its EPSG code at https://epsg.io/. To do so simply type the projection name into the search field (e.g. Pseudo-Mercator). The result page will show you the EPSG code that you can enter in this field (e.g. EPSG:3857) but also the distance unit e.g. meter or degree and the area of use where the projection works best.

If you are looking for a projection for a specific area, try out the Projection wizard page which suggests projection with specific properties for a defined area on the globe. Once you have found the appropriate projection simply click on the WKT link next to the suggested projection name, copy it to your clipboard and paste it into this field.

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