1013 - 988 = 25 hPa

25 hPa x 27 = 675 ft

1,000 + 675 = 1,675 ft approx. 1,680 ft.

 

                             1,000 ft

                                                                             1,675 ft

                                                                                      988 hPa

                             25 x 27

                             = 675 ft

 

                                                                                      1013 hPa