ProjNet4GeoAPI-For-Unity

Synopsis

This library allows processing geo-coordinates in Unity. It is based on NetTopologySuite's ProjNet4GeoAPI which is an extended port of ProjNet.

Motivation

As Unity relies on float-based coordinate reference system. Thus, the immediate processing of geo-coordinates (double) in Unity induces a significant loss of precision. To address this issue, this library provides methods for ad-hoc coordinate transformation.

flowchart LR
id1{{Geographic Coordinates}}
id2{{WGS84/UTM Coordinates}}
id3{{Unity Coordinates}}

id1-->id2
id2-->id1
id2-->id3
id3-->id2

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Installation

To add this library to your project, you can use the Package Manager:

Go to the package manager and click on “Install package from git URL” and add this URL:

https://github.com/postert/ProjNet4GeoAPI-For-Unity.git

Configuration

For the transformation into Unity coordinates, the library requires the specification of a projected reference point, which corresponds to the origin of Unity's coordinate system and the point's WGS84/UTM coordinate reference system (CRS). Geo-coordinates are placed relative to this point in Unity's Scene. The point and CRS must be specified in the CoordinateTransformer script.

Required Parameters and examples

1. WGS84/UTM coordinate reference system for your location (e.g. via mangomap.com)
   1. Estimate the UTM Zone (e.g. 32 for Hamburg in Germany)
   2. Estimate the Hemisphere whether your location is in the Northern Hemisphere or Southern Hemisphere (e.g. Northern Hemisphere for Hamburg)
2. UTM coordinates of the projected reference point (e.g. via coordinates-converter.com)
   1. Estimate the East value of the projected reference point (e.g. 566600 E for the Lohsepark in Hamburg)
   2. Estimate the North value of the projected reference point (e.g. 5933000 N for the Lohsepark in Hamburg)
   3. Provide the Altitude value of the projected reference point (e.g. 0 in the German altitude reference system DHHN2016)

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "id": 1,
      "properties": {
        "ID": 0
      },
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
              [10.0050334941202,53.5416751454004],
              [10.0065422978258,53.541662455265],
              [10.0065636189796,53.5425611772512],
              [10.0050547833268,53.5425738678005],
              [10.0050334941202,53.5416751454004]
          ]
        ]
      }
    }
  ]
}

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Apply Parameters

To apply the parameters, add one CoordinateTransformer script to the Unity Scene and provide the previously described reference point and its WGS84/UTM coordinate reference system accordingly. (The script can be added to an arbitrary GameObject (GO). It is not necessary to reset the GO's transform to the default values.)

Example of Coordinate Transformation Execution

Coordinate transformations can be executed via the CoordinateTransformer, which is defined in the GeocoordinateTransformer namespace. CoordinateTransformer provides the following six methods for immediate coordinate conversion.

// 1. Import the library's namespace
using GeocoordinateTransformer;

// ...

// 2. Define example coordinates to transform
private GeographicCoordinates geographicTestCoordinates = new(latitude: 53.5417104602435, longitude: 10.0051097859429, altitude: 4.25);
private UTMCoordinates utmTestCoordinates = new(east: 566605, north: 5933004, altitude: 3);
private Vector3 unityTestCoordinates = new(x: 1, y: 4, z: 5);

// ...

// 3. Find CoordinateTransformer with associated parameters in the Unity Scene
CoordinateTransformer coordinateTransformer = GameObject.FindAnyObjectByType<CoordinateTransformer>();

// 4. Execute coordinate transformation

// 4.1 GeographicCoordinates ⇄ Vector3 (Unity)
Vector3 unityCoordinates1 = CoordinateTransformer.GetUnityCoordinates(geographicTestCoordinates);
GeographicCoordinates geographicCoordinates1 = CoordinateTransformer.GetGeographicCoordinates(unityCoordinates);

// 4.2 UTMCoordinates ⇄ Vector3 (Unity)
Vector3 unityCoordinates2 = CoordinateTransformer.GetUnityCoordinates(utmTestCoordinates);
UTMCoordinates utmCoordinates2 = CoordinateTransformer.GetUTMCoordinates(unityCoordinates);

// 4.3 GeographicCoordinates ⇄ UTMCoordinates
GeographicCoordinates geographicCoordinates3 = CoordinateTransformer.GetGeographicCoordinates(utmTestCoordinates);
UTMCoordinates utmCoordinates3 = CoordinateTransformer.GetUTMCoordinates(geographicTestCoordinates);

For a more comprehensive overview, have a look at the documentation and use the Sample Scene as a starting point.

Sample Scene (included in Library)

A sample Unity Scene is included in the library and can be added to the Assets folder via an import in Unity's Package Manager:

SampleScene contains a Plane, a CoordinateTransformer, and a CoordinateTransformerTest GameObject. The Plane visualizes the geo-coordinates associated with Unity's coordinate system's origin. The CoordinateTransformer GO contains the CoordinateTransformer component, described in the Apply Parameters section. The CoordinateTransformerTest GO provides test functionality to either place the latter GO according to the provided coordinates or to print the GO's current location as geo-coordinates.

Limitations

The current implementation does not support floating origins. Thus, the float-induced limited spatial extent of Unity's scene is not immediately addressed in this library. However, the library can still serve a foundation of these approaches, as the CoordinateTransformer can be updated and the Scene's content be moved within the Scene accordingly.