API Reference > imodeljs-common > Geometry > GeodeticTransformProps > sourceEllipsoid sourceEllipsoid sourceEllipsoid: undefined | GeodeticEllipsoidProps The complete definition of the source geodetic ellipsoid referred to by ellipsoidId. The source ellipsoid identifier enables obtaining the shape of the Earth mathematical model for the purpose of performing the transformation. Defined in core/common/src/geometry/GeodeticDatum.ts Line 346 Last Updated: 11 June, 2024