code: public Coordinate ecefToEnu( Coordinate cEcef ) {
          double deltaX = cEcef.x - _ecefROriginX;
          double deltaY = cEcef.y - _ecefROriginY;
          double deltaZ = cEcef.z - _ecefROriginZ;
  
          double[][] deltas = new double[][]{{deltaX}, {deltaY}, {deltaZ}};
          RealMatrix deltaMatrix = MatrixUtils.createRealMatrix(deltas);
  
          RealMatrix enuMatrix = _rotationMatrix.multiply(deltaMatrix);
          double[] column = enuMatrix.getColumn(0);
  
          return new Coordinate(column[0], column[1], column[2]);
      }
docs: Converts an Earth-Centered Earth-Fixed (ECEF) coordinate to ENU.
  
  @param cEcef the ECEF coordinate.
  @return the ENU coordinate.
  @throws MatrixException