Drawing property boundaries from parcel data

CloudApartments · April 3, 2024, 8:14am

I have the lat/lon values that describe the boundaries of various properties. Any pointers on how I can place them on a map and draw the boundaries? Mostly I’m interested in making sure I’m drawing from the right place, but if anyone has any tips on rendering 3D lines in Unity I won’t complain…

CloudApartments · April 3, 2024, 4:36pm

ok - I’m halfway there. I figured out how to draw the points in Unity space with LineRenderer, and I know the CesiumGeoReference has conversion functions, but now I don’t know where the docs are for the CesiumForUnity objects…

janine · April 9, 2024, 2:31pm

Hi @CloudApartments, welcome to the community!

To check my understanding – it sounds like you want to convert Unity positions to lat/lon coordinates (or vice versa)? First, you can use the following functions to convert between Unity and Earth-Centered, Earth-Fixed (ECEF) coordinates:

github.com

CesiumGS/cesium-unity/blob/fdecc86696f7d0754f0e6322c75636ea2a9590ad/Runtime/CesiumGeoreference.cs#L444-L472


      
          /// <summary>
          /// Transform a Unity position to Earth-Centered, Earth-Fixed (ECEF) coordinates. The position should generally
          /// not be 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="unityPosition">The Unity position to convert.</param>
          /// <returns>The ECEF coordinates in meters.</returns>
          public double3
              TransformUnityPositionToEarthCenteredEarthFixed(double3 unityPosition)
          {
              this.Initialize();
              return math.mul(this._localToEcef, new double4(unityPosition, 1.0)).xyz;
          }
          
          /// <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.

This file has been truncated. show original

Then, you can use these functions to convert between ECEF and lat / lon coordinates:

github.com

CesiumGS/cesium-unity/blob/fdecc86696f7d0754f0e6322c75636ea2a9590ad/Runtime/CesiumWgs84Ellipsoid.cs#L54-L74


      
              /// <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);
          
              /// <summary>
              /// Convert Earth-Centered, Earth-Fixed (ECEF) coordinates to longitude, latitude, and height.
              /// </summary>
              /// <param name="earthCenteredEarthFixed">The ECEF coordinates in meters.</param>
              /// <returns>
              /// 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.
              /// </returns>
              public static partial double3
                  EarthCenteredEarthFixedToLongitudeLatitudeHeight(double3 earthCenteredEarthFixed);
          }

Our docs are in the form of comments above the Cesium for Unity classes / methods. We’re aware that this isn’t the easiest to find, so if you have any feedback for us, feel free to chime in on this Github issue.

Let us know if that resolves your issue, or if you have any followup questions!

CloudApartments · April 10, 2024, 4:15pm

Hi!

Thanks for the reply. I was actually looking for the reverse - converting lat/lon to Unity space. But I figured it out:

        double3 earthPosition = new double3(lat, lon, height);
        double3 ecefPosition = CesiumWgs84Ellipsoid.LongitudeLatitudeHeightToEarthCenteredEarthFixed(earthPosition);
        double3 unityPosition = georeference.TransformEarthCenteredEarthFixedPositionToUnity(ecefPosition);

It was a little weird since the Ellipsoid is static, but the geoReference is not. But it works.

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Drawing property boundaries from parcel data

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