code: public void equiToLatLon(double x , double y , GeoLL_F64 geo ) {
  		geo.lon = (x/width - 0.5)*GrlConstants.PI2;
  		geo.lat = (y/(height-1) - 0.5)*GrlConstants.PI;
  	}
docs: Converts the equirectangular coordinate into a latitude and longitude
  @param x pixel coordinate in equirectangular image
  @param y pixel coordinate in equirectangular image
  @param geo  (output)