double surfaceElevation = this.computeSurfaceElevation(dc.getSurfaceGeometry(), globe,
position.getLatitude(), position.getLongitude());
Vec4 v1 = globe.computePointFromPosition(position.getLatitude(), position.getLongitude(),
position.getElevation());
Vec4 v2 = globe.computePointFromPosition(position.getLatitude(), position.getLongitude(),
surfaceElevation);
Vec4 referenceCenter = v1;
v1 = v1.subtract3(referenceCenter);
v2 = v2.subtract3(referenceCenter);