(7) In the seventh column, record the "BASE STATION ALTIMETER READING." The "BASE STATION
ALTIMETER READING" is interpolated directly from the station record of the base station altimeter to
the probable reading at the minute the field observation was made.
(8) In the eighth column, record the "INDICATED DIFFERENCE." 'INDICATED DIFFERENCE" represents
the apparent difference in elevation between the observed base station altitude and the observed field
altitude, and is obtained by algebraically subtracting the value in column seven from the value in column
6 directly opposite.
(9) In the ninth column, enter the combined correction factor for temperature and relative humidity. To
establish this correction factor, use the wet and dry bulb reading shown in column 3 and apply the
(10) In the tenth column, enter the correction for altitude above or below altimeter scale reading of 450
(11) In the eleventh column, enter the latitude correction (correction for north or South of the equator shown
(12) In the twelfth column, enter the total correction factor. This factor is obtained by adding the corrections
entered in columns 9, 10, and 11.