(1) In the first column of the form, record the station name and number and such brief description as may
facilitate identification. Any marked change in the weather such as rain or wind squall should be noted in
(2) In the second column, record the time of each field observation to the nearest minute.
(3) In the third column, record the mean wet and dry bulb thermometer readings. These means are the
averages of the wet and dry bulb readings obtained at the field and base stations.
(4) In the fourth column, record the field altimeter reading for the base station and each point observed.
(5) In the fifth column, record the "INDEX DIFFERENCE." This difference is the algebraic difference of the
base station altimeter reading minus the field altimeter reading taken at the base station.
(6) In the sixth column, center the "FIELD INDEXED" computation. "FIELD INDEXED" shows field altimeter
readings changed to correspond with the initial station altimeter reading by applying the index difference
in turn to each of the field instrument observations. Should it be convenient to set the two instruments to
the same value for the initial reading at the base station, no entries need be made in columns 5 and 6.