GeoJSON

The GeoJSON package for Netherlands3D exposes the GeoJSON.net package and an additional suite of features to work with it.

Installing

This package is provided through OpenUPM, to install it using the CLI you can perform the following:

$ openupm add eu.netherlands3d.geojson

or, you have to add https://package.openupm.com as a scoped registry with, at least, the following scopes:

• eu.netherlands3d
• com.virgis

Usage

Before we start, in your project's Assets folder you need a file called link.xml -if it doesn't exist- with the following content:

<linker>
	<assembly fullname="GeoJSON.NET" preserve="all"></assembly>
</linker>

This is needed because GeoJSON.net provides additional JSON.net converters, which use reflection to be detected. Without this exception, the linker of Unity will filter these converters away because it thinks it is dead code.

Deserializing from GeoJSON

Since GeoJSON.net is a wrapper around JSON.net, deserializing a GeoJSON json file is a matter of the following:

    var featureCollection = JsonConvert.DeserializeObject<FeatureCollection>(jsonString);

For more information on the usage of GeoJSON.net, see their repository: https://github.com/ViRGIS-Team/GeoJSON.Net

Getting a Feature's identifier

The GeoJSON specification mentions that when a Feature has an identifier, you should add a field id. In practice, some providers do not do this but instead add a property id, ID, objectid or OBJECTID.

To make it easier for consumers to get the identifier of a feature, an extension method TryGetIdentifier() is introduced that checks each potential source of identifiers in order. A parameter can be provided as a default, for when no identifying property was present.

Example:

    string id = feature.TryGetIdentifier("Feature" + featureIndex);

Getting the EPSG identifier

The Coordinate System for GeoJSON is, by default, the EPSG:4326 variant of WSG-84. But a GeoJSON extension allows providers to add their own CRS specifiers.

if a feature has a Named CRS specified using an EPSG urn, you can use the method EPSGId() to attempt to get the EPSG numeric code that is specified. If none is specified, 4326 is returned.

Example:

    var epsgId = featureCollection.EPSGId();

Getting the Bounding Box when absent

The bbox property in GeoJSON is optional, but sometimes you still need the bounding box of all features combined in a FeatureCollection.

To do this, an extension method is introduced called DerivedBoundingBoxes(), that will calculate a total bounding box based on the features' extents.

Example:

    double[] boundingBox = featureCollection.BoundingBoxes ?? featureCollection.DerivedBoundingBoxes();

Moving a GameObject to the center of a FeatureCollection

Sometimes you need to move an object, such as a Camera or DecalProjector, to the location of a feature collection. The MoveToCenterOfFeatureCollection MonoBehaviour is can do that with a given gameobject, or the current when none is specified.