Geodata. Coordinates and maps in KulturNav

Entities in various information categories in KulturNav can be placed on the map with a coordinate point:

  • Organizations. Authorities for legal entities/organizations.
  • Building Facilities. A collective building environment or a building complex.
  • Buildings. An independent building structure.
  • Structures. Roads, railways, bridges, etc.
  • Places. Places, place names, building names, and administrative divisions.
  • Events. Named historical events.

Coordinates and Coordinate System

A coordinate point consists of the following fields:

  • Identity. An identity of the point, such as an identifying number from measurement, digitization, or other data capture.
  • Coordinate System. Specifies the coordinate system/projection in which the point is located. The coordinate system is defined as a term in the dataset Spatial reference systems. Coordinate systems are chosen from a list.
  • Latitude (Northing). Coordinate value on the axis where the value increases towards the north. Specified as a decimal number.
  • Longitude (Easting). Coordinate value on the axis where the value increases towards the east. Specified as a decimal number.
  • Height. Elevation value (Z-value). Specified as a decimal number.
  • Source. Source where the coordinate point was captured, for example, from another system.
  • Precision. Coordinate precision specified as a number. The number defines how many decimals in the coordinates correspond to the point's actual precision in WGS 84.
  • Status. The scope of the coordinate: Geolocated, Approximate och Calculated

A post can have one or more coordinate points. Coordinates specified in a different coordinate system than the one used for our base map (Google Maps; WGS 84 (EPSG:4326)) are automatically projected to be displayed on the map.

Note that KulturNav's property schema includes an experiment with handling more complex geometries in the field geometry.wkt. Unfortunately, these are not fully handled in the current version.

Precision (in WGS 84)

The property precision defines how many decimals in the coordinates correspond to the point's actual accuracy. The coordinate "59.04112, 9.99743" with precision: 4 has actual accuracy equivalent to "59.0411, 9.9974". In practice, precision: 3=100 m, 4=10 m, 5=1 m, 6=0.1 m (decimeter), 7=0.01 m (cm), and 8=0.001 m (mm). The values are approximate and apply to WGS 84 (measured at the equator).

Maps

Posts with coordinates can be displayed on a map (Google Maps):

Post

A post with a coordinate point shows its location under the Map tab on the post. The coordinate itself is visible under the post's Facts tab. The coordinate is edited in the Geodata section of the editing form or if you choose the Geodata property in the suggestion panel.

Dataset

A dataset containing posts with coordinates has the ability to overview the content of the dataset under the Contents tab when selecting the view mode Map. This shows a map of all published coordinates in the dataset.

Folder

You can also view a map of the contents of a folder if the folder contains published posts with coordinates (or datasets containing published posts with coordinates).

Map Data and Map Features

To increase the map display speed, we have stored the map in a cache. When needed, update the map by clicking the Update button (visible if you have editing rights to the dataset). This may be necessary if you have added points since the last update or changed geodata or the name of the post in the dataset.

If a dataset (or folder) contains more than 2000 coordinates, the points on the map will be grouped into clusters. Click on a cluster to zoom in. When you zoom in far enough, the individual posts will be shown as point markers.

If you click on a point, a popup dialog with information about the post will appear. Click on the link to open the post in a new tab in the browser. If you hover over a point, the post's name is displayed as a label.

Keep in mind that map data is generated with labels and field information in one language, typically the language chosen as the primary language in the dataset. If there is no primary language, it is selected based on the chosen website language.

Filter Posts with Coordinates in Dataset

A dataset containing posts with coordinates can be filtered to show posts with coordinates. Posts with coordinates are displayed in the dataset listing (and search results) with the icon  .

Export Geodata

You can export geodata and a selection of other properties to a file for use in, for example, a GIS. There are two export formats:

  • GeoJSON. You can export a dataset in GeoJSON format through the Function menu | Export dataset (GeoJson). Note that coordinates in GeoJSON are always in WGS 84 (EPSG:4326).

  • CSV with Coordinates. You can export a dataset as a semicolon-separated text file through the Function menu | Export dataset (CSV with Coordinates). This exports both data in WGS 84 (EPSG:4326) and your stored coordinate system into the file.

Machines and other apps access geodata from a dataset with an API method (/api/geoJSON/{dataset-uuid}) that streams coordinates from the specified dataset in GeoJSON format. You can also specify /{uuid}.geojson to retrieve geodata and a selection of other properties from a dataset, folder, or individual post that has geodata.