Converting longitude/latitude to world coordinates

saleh01 · December 5, 2024, 7:25pm

Hello everyone,
I am just starting to work with Unity and Cesium for the very first time. I am writing a C# script that is supposed to receive some longitude and latitude coordinates, convert them to world coordinates, and add place some spheres on the globe at these coordinates. I could not find anything about this issue. Could you please let me know how to go about this? Thank you all in advance.

janine · December 9, 2024, 4:19pm

Hi @saleh01, welcome to the community!

First, I recommend attaching a CesiumGlobeAnchor component to each sphere. The component will keep track of the globe-relative position of the object (in long / lat coordinates), and it automatically updates the Unity position to keep track of this. You can learn more about Cesium Globe Anchor by following this tutorial!

However, if you would prefer to place the objects manually, then you can check out the following functions. First, you’ll have to call CesiumWgs84Ellipsoid.LongitudeLatitudeHeightToEarthCenteredEarthFixed to convert to ECEF coordinates.

github.com

CesiumGS/cesium-unity/blob/6a86882e8a14432b02a5738c2d68b8427db7d6f7/Runtime/CesiumWgs84Ellipsoid.cs#L54-L62


      
          /// <summary>
          /// Convert longitude, latitude, and height to Earth-Centered, Earth-Fixed (ECEF) coordinates.
          /// </summary>
          /// <param name="longitudeLatitudeHeight">
          /// The longitude (X) and latitude (Y) are in degrees. The height (Z) is in meters above the ellipsoid,
          /// and should not be confused with a geoid, orthometric, or mean sea level height.</param>
          /// <returns>The ECEF coordinates in meters.</returns>
          public static partial double3
              LongitudeLatitudeHeightToEarthCenteredEarthFixed(double3 longitudeLatitudeHeight);

Then, given those ECEF coordinates, you’ll want to call TransformEarthCenteredEarthFixedPositionToUnity on the CesiumGeoreference.

github.com

CesiumGS/cesium-unity/blob/6a86882e8a14432b02a5738c2d68b8427db7d6f7/Runtime/CesiumGeoreference.cs#L581-L594


      
          /// <summary>
          /// Transform an Earth-Centered, Earth-Fixed position to Unity coordinates. The resulting position should generally
          /// not be interpreted as a Unity _world_ position, but rather a position expressed in some parent
          /// GameObject's reference frame as defined by its Transform. This way, the chain of Unity transforms
          /// places and orients the "globe" in the Unity world.
          /// </summary>
          /// <param name="earthCenteredEarthFixed">The ECEF coordinates in meters.</param>
          /// <returns>The corresponding Unity coordinates.</returns>
          public double3
              TransformEarthCenteredEarthFixedPositionToUnity(double3 earthCenteredEarthFixed)
          {
              this.Initialize();
              return math.mul(this._ecefToLocal, new double4(earthCenteredEarthFixed, 1.0)).xyz;
          }

I hope that helps! Let us know if you have any follow-up questions.

Topic		Replies	Views
About Unity coordinates to longitude and latitude coordinates Cesium for Unity	13	3047	February 26, 2024
On transforming longitude and latitude into unity coordinates Cesium for Unity	2	1090	December 29, 2022
How to accurately correspond longitude and latitude with world coordinates? Cesium for Unity	1	1130	February 14, 2023
How do I convert latitude and longitude from Google Maps to Cesium For Unity Cesium for Unity	1	213	May 13, 2024
Setting Coordinates in Cesium Globe Anchor Cesium for Unity	1	24	December 9, 2024

Converting longitude/latitude to world coordinates

Related topics