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GeoJSON Support

Netherlands3D enables users to import and work with GeoJSON data seamlessly. Below is a breakdown of how GeoJSON files are supported, including file handling, parsing, coordinate transformation, and more.

Importing

Netherlands3D supports .json and .geojson file extensions by default. For custom file types, you can extend support by modifying:

  • FileOpen script: Enables selection of additional file types.
  • FileTypeAdapter: Handles the processing of new file types.

GeoJSON files are uploaded and embedded as assets within the open NL3D project. When opened from a URL, pointing to GeoJSON files ( e.g., https://raw.githubusercontent.com/blackmad/neighborhoods/refs/heads/master/utrecht.geojson), these are added as remote assets, ensuring they reload every time a project is opened.

Parsing and Performance

To prevent application freezes when importing large files, GeoJSON parsing is spread across multiple frames. The default parsing time per frame is 0.01 seconds, but this value can be adjusted by modifying the maxParseDuration variable in GeoJSONLayer.cs.

Supported Feature Types

Netherlands3D supports the following GeoJSON feature types:

  • Polygon
  • MultiPolygon
  • LineString
  • MultiLineString
  • Point
  • MultiPoint

Features of the same type are combined into a single layer in the application:

  • Polygon and MultiPolygon → One layer.
  • LineString and MultiLineString → One layer.
  • Point and MultiPoint → One layer.

Coordinate Transformation

GeoJSON coordinates are converted to Unity coordinates using the eu.netherlands3d.coordinates package. The transformation leverages the parsed CRS (Coordinate Reference System).

CRS Support

  • Netherlands3D supports the "Named CRS" feature described in the original pre-2018 GeoJSON specification (see details here), enabling backwards compatibility for older GeoJSON files that define their own CRS.
  • Support for the "Linked CRS" variant is not provided.
  • Custom CRS definitions are not supported in the current GeoJSON specification, but legacy files using "Named CRS" are still supported.

Visualization and Appearance

A material can be assigned to a GeoJSONLayer to control the visualization's appearance. This allows for customization of how imported GeoJSON features are displayed in the 3D environment.

Error Handling

Netherlands3D includes error handling for GeoJSON imports. If parsing fails, an event is invoked to display error messages on-screen, ensuring users are informed of any issues during the import process.

Troubleshooting

If GeoJSON data does not display correctly in Netherlands3D, follow these steps to verify data correctness before debugging the code:

  1. Open the file in QGIS: Check if QGIS can successfully display the data. If QGIS cannot load the file, the data may be incorrect.
  2. Validate the GeoJSON structure and geometry: Use the GeoJSON Validator to confirm the file’s structure and geometry are valid.
  3. Test the file in GeoJSON.io: Try loading the file in GeoJSON.io to verify if the data renders correctly.

These steps help ensure the GeoJSON file is correct and usable, minimizing unnecessary debugging in the code.