ships, aircraft, and submarines all use the same code.
Surface ships and some aircraft must take a surface
weather observation at the same time the BT
observation is made.
As an Aerographers Mate, you will be required to
encode or at least review bathythermograph data for
dissemination. Besides its immediate operational use,
BT data will also be used to develop oceanographic
historical data bases. Therefore, it is imperative that a
quality control check be conducted prior to
transmission of the data.
Additional information on conducting and
encoding bathythermograph observations is contained
in OPNAVINST 3141.1, Collection and Reporting of
Bathythermograph Observations, and in NAVMET-
OCCOMINST 3140.1, United States Navy Meteoro-
logical and Oceanographic Support System Manual.
The symbolic format of the BATHY code is shown
in table 2-2.
The bathythermograph code is sent as a single
message composed of four sections of data. In table 2-2,
groups in parenthesis are optional. Section 1 contains
identification data and may contain meteorological
data; section 2 contains the instrumentation and
recorder type, and the depth/temperature information;
section 3 reports water depth and surface current
(optional); and section 4 is the ship or ocean station
The identification data section contains the
mandatory data identifier; the year, month, and day
group; the actual time of the observation; a latitude and
longitude group; and the optional wind and air
The first group in section 1 is the data identifier,
which is reported as "JJYY" for all ship, aircraft, and
submarine BATHY observations.
A group not seen in many other codes is the
YYMMJ. The YY is the UTC day of the month, while
Table 2-2.Symbolic Format of WMO Code FM 63-X
MM is the month in two digits, and J is the last digit of
the year. For example, "JJYY 22037" indicates that a
BATHY observation was taken on the 22d day of
The time of the observation is encoded in group
GGgg/ in UTC. The GG is the hour, and gg is the
minutes after the hour. When the code is transmitted
with depth and temperature reported in metric units
(meters and degrees Celsius), the time is followed by a
slant. If the operator is unable to convert observations
from English units to metric units, the slant is changed
to a 9. Navy bathythermograph operators will normally
convert from English to metric units.
The latitude and longitude of the observation are
reported in two groups, QcLaLaLaLa and LOLOLOLOLo.
The Qc is the quadrant of the globe using WMO code
table 3333 (see appendix III); LaLaLaLa is the latitude in
degrees and minutes; and LoLoLoLoLo is the longitude
in degrees and minutes. This is the only code routinely
used that reports latitudes and longitudes in degrees and
minutes. All of the other codes report in degrees and
tenths of a degree.
The optional wind group, iuddff, is reported by
most surface ships, but need not be reported by
submarines and aircraft. The group starts with an
indicator for wind speed, iu, found in WMO code table
1853. This is not the same indicator used for wind speed
in the land and ship Synoptic codes (WMO Code 1855).
Navy ships use only code figure 3 to indicate winds
measured in knots in the bathythermograph code. Wind
direction is reported in hundreds and tens of degrees in
dd, and speed is reported to the nearest whole knot in ff.
NOTE: Instructions accompanying the log sheet
state that iu should be encoded as a "0" (wind speed in
meters) or a "1" (wind speed in knots). In the coded
message, only a "3" (uncertified wind measuring
instruments used) should be encoded as the first digit of
the wind group.
JJYY YYMMJ GGgg/ or (GGgg9) QcLaLaLaLa
LoLoLoLoLo (Iuddff) (4snTTT)
8888Kj IXIXIXXRXR ZOZOTOTOTO . . . . . ZnZnTnTnTn
(66666 1ZdZdZdZd k5DcDcVcVc)
D. . . .D or 99999 A1bwnbnbnb
Ships should also report the optional outside air
temperature in group 4snTTT. The 4 is the temperature
indicator; sn is the temperature sign (0 for positive or
zero, and 1 for negative temperatures); and TTT is the
air temperature to the nearest tenth degree, usually in
This group is not reported by
submarines and aircraft.
Shipboard bathythermograph operators should
report both wind and air temperature, and insert these
code groups between data groups 5 and 6 on the form.