B5-6 PREPARATION OF CHARTS 
3.3 Data to be Entered in Data Block Columns. Data will be entered in 
the columns headed Pressure, Temperature, Relative Humidity, and Dew 
Point in accordance with the following instructions. 
3.3.1 Pressure. Two entries are required for pressure at all levels 
except the surface; these are under "'contact' and "mb." 
a. Contact. For those upper-levels for which the pressure is de- 
termined by the baroswitch, enter the contact value to the 
nearest tenth, as obtained from the recorder record. For those 
upper-levels for which the pressure is determined by the hyp- 
someter, enter the hypsometer reading to the nearest tenth of 
an ordinate, as obtained from the recorder record. 
b. Millibars. For the surface level enter the surface pressure to 
the nearest whole mb (see JB4-4.3). Obtain this value from the 
"Surface Observation at Release" block. For upper levels, 
enter the pressure values as follows: 
(1) Whenever pressure data are derived from aneroid mea- 
surements, pressure values will be entered in whole 
millibars. If however, at high altitudes, the rounding of 
pressure to whole millibar values results intwoor more 
Significant levels having the same value, pressure for 
those levels only will be entered in Data Block C to the 
nearest 0.5 mb whenever the value is between 19.5 and 
10.0 mb, and to the nearest0.1 mb. whenever the value is 
less than 10 mb. In such instances, note in remarks that 
pressure value for level numbered _ is shown totenths of 
a millibar. This does not imply that the aneroid baroswitch 
is capable of measurements to the indicated accuracy. 
For example, two pressures rounded off to the nearest 
mb both have a value of 6 mb. If both were read to the 
nearest tenth they would be 6.4 and 5.8. Select the one 
furtherest from the rounded value, and enter to tenths. 
The entries would then be 6.4and6.If both were selected 
for transmission 6.4 would be transmitted 064 and 6 would 
be transmitted as 060. 
(2) Whenever pressure data are derived from hypsometer 
measurements pressure values will be entered in whole 
millibars whenever the value is 20 mb, or greater, to the 
nearest 0.5 mb, whenever the value is between 19.5 and 
10.0 mb, and to the nearest 0.1 mbwhenever the value is 
less than 10 mb. (WB,N) Insert in remarks ''Hypsometer 
data begin with level. Pressures less than 20 mb are 
shown to tenths of mbs." 
l=1=69) FMH#3 
