DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

NONRESIDENT
TRAINING
COURSE
October 1992
Time Conversion
NAVEDTRA 14252
DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.
Although the words he, him, and
his are used sparingly in this course to
enhance communication, they are not
intended to be gender driven or to affront or
discriminate against anyone.
i
PREFACE
By enrolling in this self-study course, you have demonstrated a desire to improve yourself and the Navy.
Remember, however, this self-study course is only one part of the total Navy training program. Practical
experience, schools, selected reading, and your desire to succeed are also necessary to successfully round
out a fully meaningful training program.
THE COURSE: This self-study course is organized into subject matter areas, each containing learning
objectives to help you determine what you should learn along with text and illustrations to help you
understand the information. The subject matter reflects day-to-day requirements and experiences of
personnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers
(ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational or
naval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classifications
and Occupational Standards, NAVPERS 18068.
THE QUESTIONS: The questions that appear in this course are designed to help you understand the
material in the text.
VALUE: In completing this course, you will improve your military and professional knowledge.
Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you are
studying and discover a reference in the text to another publication for further information, look it up.
1992 Edition Prepared by
CTRCS Richard W. Piatt
Published by
NAVAL EDUCATION AND TRAINING
PROFESSIONAL DEVELOPMENT
AND TECHNOLOGY CENTER
NAVSUP Logistics Tracking Number
0504-LP-026-8860
ii
Sailors Creed
I am a United States Sailor.
I will support and defend the
Constitution of the United States of
America and I will obey the orders
of those appointed over me.
I represent the fighting spirit of the
Navy and those who have gone
before me to defend freedom and
democracy around the world.
I proudly serve my countrys Navy
combat team with honor, courage
and commitment.
I am committed to excellence and
the fair treatment of all.
iii
CONTENTS
TOPIC PAGE
1. Time theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
2. Time-Conversion Computation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
3. Geography and Plotting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1
iv
INSTRUCTIONS FOR TAKING THE COURSE
ASSIGNMENTS
The text pages that you are to study are listed at
the beginning of each assignment. Study these
pages carefully before attempting to answer the
questions. Pay close attention to tables and
illustrations and read the learning objectives.
The learning objectives state what you should be
able to do after studying the material. Answering
the questions correctly helps you accomplish the
objectives.
SELECTING YOUR ANSWERS
Read each question carefully, then select the
BEST answer. You may refer freely to the text.
The answers must be the result of your own
work and decisions. You are prohibited from
referring to or copying the answers of others and
from giving answers to anyone else taking the
course.
SUBMITTING YOUR ASSIGNMENTS
To have your assignments graded, you must be
enrolled in the course with the Nonresident
Training Course Administration Branch at the
Naval Education and Training Professional
Development and Technology Center
(NETPDTC). Following enrollment, there are
two ways of having your assignments graded:
(1) use the Internet to submit your assignments
as you complete them, or (2) send all the
assignments at one time by mail to NETPDTC.
Grading on the Internet: Advantages to
Internet grading are:
you may submit your answers as soon as
you complete an assignment, and
you get your results faster; usually by the
next working day (approximately 24 hours).
In addition to receiving grade results for each
assignment, you will receive course completion
confirmation once you have completed all the
assignments. To submit your assignment
answers via the Internet, go to:
http://courses.cnet.navy.mil
Grading by Mail: When you submit answer
sheets by mail, send all of your assignments at
one time. Do NOT submit individual answer
sheets for grading. Mail all of your assignments
in an envelope, which you either provide
yourself or obtain from your nearest Educational
Services Officer (ESO). Submit answer sheets
to:
COMMANDING OFFICER
NETPDTC N331
6490 SAUFLEY FIELD ROAD
PENSACOLA FL 32559-5000
Answer Sheets: All courses include one
scannable answer sheet for each assignment.
These answer sheets are preprinted with your
SSN, name, assignment number, and course
number. Explanations for completing the answer
sheets are on the answer sheet.
Do not use answer sheet reproductions: Use
only the original answer sheets that we
providereproductions will not work with our
scanning equipment and cannot be processed.
Follow the instructions for marking your
answers on the answer sheet. Be sure that blocks
1, 2, and 3 are filled in correctly. This
information is necessary for your course to be
properly processed and for you to receive credit
for your work.
COMPLETION TIME
Courses must be completed within 12 months
from the date of enrollment. This includes time
required to resubmit failed assignments.
v
PASS/FAIL ASSIGNMENT PROCEDURES
If your overall course score is 3.2 or higher, you
will pass the course and will not be required to
resubmit assignments. Once your assignments
have been graded you will receive course
completion confirmation.
If you receive less than a 3.2 on any assignment
and your overall course score is below 3.2, you
will be given the opportunity to resubmit failed
assignments. You may resubmit failed
assignments only once. Internet students will
receive notification when they have failed an
assignment--they may then resubmit failed
assignments on the web site. Internet students
may view and print results for failed
assignments from the web site. Students who
submit by mail will receive a failing result letter
and a new answer sheet for resubmission of each
failed assignment.
COMPLETION CONFIRMATION
After successfully completing this course, you
will receive a letter of completion.
ERRATA
Errata are used to correct minor errors or delete
obsolete information in a course. Errata may
also be used to provide instructions to the
student. If a course has an errata, it will be
included as the first page(s) after the front cover.
Errata for all courses can be accessed and
viewed/downloaded at:
http:/ / www. advancement. cnet. navy. mi l
STUDENT FEEDBACK QUESTIONS
We value your suggestions, questions, and
criticisms on our courses. If you would like to
communicate with us regarding this course, we
encourage you, if possible, to use e-mail. If you
write or fax, please use a copy of the Student
Comment form that follows this page.
For subject matter questions:
E-mail: cryptologic.products@cnet.navy.mil
Phone: Comm: (850) 452-1688
DSN: 922-1688
FAX: (850) 452-1370
(Do not fax answer sheets.)
Address: COMMANDING OFFICER
NETPDTC (CODE N316)
6490 SAUFLEY FIELD ROAD
PENSACOLA FL 32509-5237
For enrollment, shipping, grading, or
completion letter questions:
E-mail: fleetservices@cnet.navy.mil
Phone: Toll Free: 877-264-8583
Comm: (850) 452-1511/1181/1859
DSN: 922-1511/1181/1859
FAX: (850) 452-1370
(Do not fax answer sheets.)
Address: COMMANDING OFFICER
NETPDTC (CODE N331)
6490 SAUFLEY FIELD ROAD
PENSACOLA FL 32559-5000
NAVAL RESERVE RETIREMENT CREDIT
If you are a member of the Naval Reserve, you
will receive retirement points if you are
authorized to receive them under current
directives governing retirement of Naval
Reserve personnel. For Naval Reserve
retirement, this course is evaluated at 2 points.
(Refer to Administrative Procedures for Naval
Reservists on Inactive Duty, BUPERSINST
1001.39, for more information about retirement
points.)
COURSE OBJECTIVES
In completing this nonresident training course,
you will demonstrate a knowledge of the subject
matter by correctly answering questions on the
following:
Concepts of time zone theory and time
computation
Geographic reference and direction
systems
Characteristics of maps and charts
Geographic areas of interest to the Navy
vii
Student Comments
Course Title: Time Conversion
NAVEDTRA: 14252 Date:
We need some information about you:
Rate/Rank and Name: SSN: Command/Unit
Street Address: City: State/FPO: Zip
Your comments, suggestions, etc.:
Privacy Act Statement: Under authority of Title 5, USC 301, information regarding your military status is
requested in processing your comments and in preparing a reply. This information will not be divulged without
written authorization to anyone other than those within DOD for official use in determining performance.
NETPDTC 1550/41 (Rev 4-00)
TOPIC 1
TIME THEORY
The development of high-speed trans-
portation and communications has reduced the
relative size of the earth to the extent that
people can now travel from North America to
Europe in less than 3 hours; a message can be
sent from any place on the earth and arrive at
any other place in seconds; and weapons of
every description can be deployed from
subsurface, surface, air, and space platforms.
As this technology was emerging, it became
apparent that nations could no longer think in
terms of local times and conditions. A
standard time reference covering the entire
world was needed. Without a standard time
system, a routine airline flight plan for a
Paris-to-San Francisco flight might read like
this:
Depart Paris1200 Local Time
Arrive London1130 Greenwich
Mean Time
Depart London1200 Greenwich
Mean Time
Arrive New York0950 Eastern
Standard Time
Depart New York1050 Eastern
Standard Time
Arrive Denver0930 Mountain
Standard Time
Depart Denver1000 Mountain
Standard Time
Arrive San Francisco0930 Pacific
Standard Time
In computing the elapsed time for the
flight, or for any part of it, individual
calculations are necessary to adjust for time
zone changes. There also might be changes for
daylight saving time (DST) or other local
differences. Time computations are easier if all
times are computed on a common worldwide
basis. Then, our flight plan is simplified,
looking like this:
Depart Paris1100 Greenwich
Mean Time
Arrive London1130 Greenwich
Mean Time
Depart London1200 Greenwich
Mean Time
Arrive New York1450 Greenwich
Mean Time
Depart New Yorkl550 Greenwich
Mean Time
Arrive Denver1630 Greenwich
Mean Time
Depart Denver1700 Greenwich
Mean Time
Arri ve San Franci sco1730
Greenwich Mean Time
GREENWICH MEAN TIME
(GMT)
To meet the need for standardization, the
international GMT system was developed. All
countries of the world adopted its use.
GLOBAL DIVISION AND
DESIGNATORS
To compute time differences, you need to
understand the international GMT system. In
1-1
this system, the surface of the earth is divided
into 24 zones, each extending through 15 of
longitude, with the initial zone lying between
longitudes 7 east and 7 west of the prime
meridian. (Longitude is the name given to the
imaginary lines that run lengthwise, north and
south, between the North and South Poles.
They have east and west designators.) The time
system is named after Greenwich, England,
because the zero meridian passes directly
through that town. Each zone represents a
different time in the 24-hour-day cycle, with a
1-hour variation between each time zone. To
further aid in zone referencing, each time zone
has a numerical, a literal (letter) and, to aid in
the mathematical computation, a "+" or a "-"
designator.
Numerical Designators
The zero meridian (prime meridian) is the
imaginary line running down the center of the
initial time zone; thus, this time zone is
designated "0" (zero) in the numbering system.
The remaining zones are numbered consecu-
tively, 1 through 12, both east and west of 7
longitude, through 180 longitude. The
longitudes of 180 east and 180 west are the
same imaginary line. This meridian is the
International Date Line.
Lets pause to consider what appears to be
a contradiction. We stated that the earth is
divided into 24 time zones; however, we have
accounted for 25 zones (12 east of zone 0, 12
west of zone 0, and zone 0 itself, a total of 25
zones). This contradiction will be resolved
later in the discussion of the International Date
Line and the requirement to have a point at
which we shift from one day to another. For
now, lets agree there are only 24 time zones.
Literal (Letter) Designators
In addition to all zones having an assigned
number, each zone also has a letter designator.
The initial time zone, again because of its
division by the zero meridian, is designated
zone "Z" or ZULU. (Use the phonetic alpha-
bet to pronounce the letters of the time zones.)
With 25 designators, we use every letter of
the English alphabet except "J." See figure 1-1.
Like the numbering system, the letters begin
with the ZULU (0) time zone and progress to
the east and west, consecutively. The zones to
the east of ZULU are lettered "A" through "M"
(ALFA through MIKE) and the zones to the
west of ZULU are lettered "N" through "Y"
(NOVEMBER through YANKEE). Re-
member, beginning at ZULU and reading from
left to right, we have zones ALFA through
MIKE (eastern hemisphere). Returning to
ZULU and reading from right to left, we find
zones NOVEMBER through YANKEE (west-
em hemisphere). Dont forget to omit "J" in
the eastern hemisphere.
Designators "+" and "-"
Each zone has a designation of either "+"
or "-" in addition to the numerical and literal
designators. In time-conversion computations,
you will see the reason for these designators.
Learning the "+" and "-" designation
system is easy. All zones of the western
hemisphere have the designation "+." All zones
of the eastern hemisphere have the designation
"-". see figure 1-1.
PHYSICAL CHARACTERISTICS
OF TIME ZONES
With the exceptions of zones MIKE and
YANKEE, which we will discuss later, each
time zone spans 15 of longitude, with the 24
principal meridians bisecting (dividing in
half) each zone. At the equator, each degree
of longitude spans 60 nautical miles (NMs).
Thus, a time zone spans 900 NMs (15 60 =
900).
1-2
P
a
g
e

1
-
3
.
F
i
g
u
r
e

1
-
1
.

T
i
m
e

z
o
n
e

c
h
a
r
t

o
f

t
h
e

w
o
r
l
d
.
NOTE: Remember, only at the equator
is each degree of longitude equal to 60 NMs.
The natural curvature of the earth causes a
narrowing of the zones as the north or south
latitude increases. The length of a degree of
longitude gets progressively smaller the farther
it is from the equator.
Time zones generally correspond with the
principal meridians; however, sometimes they
deviate from their geographical meridians,
especially on land areas. This is common along
coastlines, in mountain ranges, and along
country borders. These deviations keep time
constant wherever possible throughout
countries, states, cities, and island chains.
See figure 1-1.
EXPRESSION OF TIME
The U.S. military services, as well as most
foreign countries, use the international 24-hour
system for expressing time. This method uses
a four-digit group, with the first two digits
denoting the hour, and the second two digits
indicating the minutes. Thus, 6:30 A.M.
becomes 0630; noon becomes 1200; 6:30 P.M.
becomes 1830. Midnight is expressed as 0000,
never as 2400. One (1) minute past midnight is
0001. The time designation 1327Z shows that
it is 27 minutes past 1:00 P.M., GMT.
To express the day of the month along
with the time, we use a six-digit group. These
six digits are nothing more than a four-digit
time, preceded by two digits indicating the
date. This six-digit group is a date-time group
(DTG). The DTG 171327Z indicates the 17th
day of the month at 1327Z.
The date element of the DTG always has
two digits. This means the dates from the 1st
through the 9th of the month must be preceded
by a zero (0) to meet this requirement (for
example, 011327Z, 021327Z, or 031327Z).
Should a month other than the current one be
intended, the standard abbreviation for the
month desired follows the DTG (for example,
011327Z JAN, 121327Z FEB, or 211327Z
MAR).
In each of the above examples, the times
were expressed in ZULU time. This is to make
you think in terms of ZULU, since ZULU zone
time is the standard time for military com-
munications . All messages, reports, and
letters containing times, use ZULU time.
This enables all mobile platforms and shore
stations to know at what time the subject of
the correspondence occurred. It becomes
simply a matter of converting the ZULU time
of the occurrence to the local time.
Obviously, there are occasions when time
must be expressed as local. In these instances,
the literal designator for the local zone is used
in exactly the same manner as the ZULU
designator was used. For example, in the
UNIFORM time zone, 171327U would indi-
cate the 17th day of the current month, 27
minutes past 1300 local time.
INTERNATIONAL DATE LINE
The International Date Line divides the
eastern and western hemispheres. It is an
imaginary line located exactly 180 east
longitude and 180 west longitude of the prime
meridian. At this point, we must understand
the special circumstances surrounding zones
MIKE and YANKEE.
Each time zone has a numerical, a literal,
and a "+" or a "-" designator, and zones MIKE
and YANKEE are not exceptions. There is,
however, a very important difference between
zones MIKE and YANKEE and all other time
zones. To understand this difference, look at
zones MIKE and YANKEE as a single time
zone of 15 of longitude, half (7) in the
eastern hemisphere, and half in the western
hemisphere. Although the two halves of this
zone share a common number (12) each half
has its own literal and "+" or "-" designator.
The eastern hemispheres half is designated
MIKE -12; the western hemispheres half is
YANKEE + 12.
1-4
Now we come to a very important point in
our discussion. Since we are considering the
MIKE and YANKEE zones to be a single
zone, it follows that the time in MIKE is
always the same as that in YANKEE. This is
where the International Date Line comes into
play, for whenever this line is crossed, whether
from east to west or from west to east, the day
must change. Since we have already estab-
lished that there is a 1-hour difference between
each of the 24 time zones, it is clear that there
is always a situation where it is a day earlier or
later in one part of the world than it is in
another.
RULE: IT IS ALWAYS THE SAME
TIME IN ZONE MIKE AS IT
IS IN ZONE YANKEE, BUT
IT IS NEVER THE SAME
DAY.
A final point of discussion involving the
International Date Line and zones MIKE and
YANKEE is the "gaining" or "losing" of a day
as the line is crossed. This is not a problem.
"Gaining" or "losing" is nothing more than a
question of semantics and should not be used
in time conversion conversation.
The formula for determining whether to
add or subtract one day from the current day at
the time of departing one hemisphere
another is:
When you cross the International
Date Line, apply the sign of the
departed hemisphere. For example,
to go from the MIKE zone into the
YANKEE zone, subtract one day.
MIKE is in the eastern (or the "-")
hemisphere. To go from the YAN-
KEE zone into the MIKE zone, add
one day. YANKEE is in the western
(or the "+") hemisphere. From "-" to
"+," subtract; from "+" to "-," add.
Another method is simply to remem-
ber to add a day when crossing the
line westbound and subtract a day
when crossing eastbound.
for
ZONE-TO-ZONE PROGRESSION
At this point, we will discuss one more
area needed for time calculation. It is
directional flow and the addition or subtraction
of an hour when progressing from one time
zone into another. Probably the best way to
remember whether to add or to subtract the
hour is to take the case of the four time zones
spanned by the United States (ROMEO
through UNIFORM).
Most of us have, at some time or other,
watched a sporting event being played on the
West Coast while we were physically located on
the East Coast. In cases where the contest was
held in the late afternoon or early evening in
California, it was frequently dark in New York.
Obviously, it was earlier in the day in
California than it was in New York. There-
fore, we can say with confidence that whenever
traveling from a westerly direction toward a
point eastward, we must add an hour each time
we pass from one time zone into another. The
opposite is also certainly true. When traveling
from an easterly direction toward a point
westward, we must subtract an hour for each
new zone entered. This rule will hold true
regardless of your location in the world: west
t o east add, east t o west subt ract .
Additionally, when the 0000 hour is reached,
the day changes accordingly.
TOPIC SUMMARY
It is absolutely essential that you
understand each of the points covered thus far
in this manual before attempting to convert
time. The following is a short review of these
principles. Test yourself. If you do not fully
understand any of them, go back and reread
the related section.
1. The international Greenwich mean
time (GMT) system was named for the town of
Greenwich, England, as the town is located
directly on the prime meridian, the point of
reference for the entire system.
1-5
2. The surface of the earth is divided into
24 time zones, each spanning 15 of longitude.
3. The initial zone is zone 0 (ZULU) and
spans the area 7 longitude east and 7
longitude west of the prime meridian (a total
of 15).
4. Each zone differs in time by 1 hour.
5. Each zone has a numerical, a literal,
and a "+" or a "-" designator (exception:
ZULU zone (0) does not have a "+" or "-"
designator).
6. The zones are numbered 1 through 12,
outwardly from zone 0, throughout both the
eastern and western hemispheres.
7. The zones east of ZULU are lettered
ALFA through MIKE, omitting JULIETT,
and each has a "-" designator.
8. The zones west of ZULU are lettered
NOVEMBER through YANKEE, and each
has a "+" designator.
9. At the equator there are 60 nautical
miles (NMs) in a degree and each time zone
spans 900 NMs; a time zone spans 15 of
l o n g i t u d e ( e x c e p t i o n : MI KE a n d
YANKEEeach span 7 of longitude).
10. The U.S. Navy uses the international
24-hour time system, expressed in four digits;
DTGs are formed by preceding the four-digit
time with a two-digit number expressing the
day.
11. The International Date Line separates
the designators MIKE and YANKEE (-12 and
+12). The date will always change when
crossing this line, regardless of the direction of
crossing. When you cross the line, apply the
sign of the departed hemisphere.
12. MIKE and YANKEE are one time
zone of 15 longitude, sharing the same
numerical designator (12). MIKE is the eastern
7 of longitude of this zone; YANKEE is the
western 7 of longitude.
13. The time will change by 1 hour
whenever a new time zone is entered: east to
west, subtract 1 hour; west to east, add 1 hour.
14. The day changes to the next or
previous day once 0000 is reached, depending
upon the direction of travel.
15. The time is always the same in MIKE
as it is in YANKEE, but it is never the same
day.
REFERENCES
Communications Instructions General, ACP
121(F), Annex A, Joint Chiefs of Staff,
Washington, DC, 15 April 1983.
1-6
TOPIC 2
TIME-CONVERSION COMPUTATION
With U.S. naval ships and aircraft
depl oyed t hroughout t he worl d, t i me
computation becomes a matter of concern to
virtually every naval member. Communicators
use ZULU time in messages and other record
communications. It is extremely important
that you know how to make time conversions
from local to ZULU time and from ZULU to
local time. Those involved in collection,
processing and reporting, and traffic analysis
must be able to make quick and accurate time
conversions throughout their working day.
CONVERSION FROM LOCAL
TIME TO ZULU TIME
We know the ZULU time zone has the
numerical designator zero (0). At this point,
the "+" or "-" assigned to each of the other
zones comes into play. To convert the local
time to ZULU time, simply add or subtract as
indicated by the sign (+ or -) of the local time
zone.
For example, we are in Pensacola, Florida,
and wish to assign a date-time group (DTG) to
a message. We will have to use ZULU time for
the message. Pensacola is in the SIERRA time
zone and is designated +6. The local date and
time is 191045S (the 19th of the month at 10:45
A.M.). Since the SIERRA time zone is +6
(Pensacola local time), add 6 to the local time
of 1045. Our answer is the conversion of
191045S to ZULU time 191645Z.
Our problem looks like this:
191045S (local DTG)
+6 (Pensacola is in zone +6)
191645Z (ZULU DTG)
NOTE: Remember, the +6 must be placed
under the "hours" of the local DTG.
RULE: FROM LOCAL TIME TO ZULU
TIMEAPPLY THE SIGN.
To check ourselves for complete under-
standing, lets take one more example of
converting local time to ZULU time. This
time we are in Kamiseya, Japan, and wish to
assign a DTG to an outgoing message. First,
we have to know the zone designation for
KamiseyaINDIA (-9). The date and time in
Kamiseya is 101800I. Using our formula, we
apply the "-" sign and subtract the local zone
(9) from the local time:
101800I (local DTG)
- 9 (Kamiseya is in zone -9)
100900Z (ZULU DTG)
These examples can help you convert local
time to ZULU time from any place in the
world. The only variations that you will
encounter involve the International Date Line
and daylight saving time (DST), each of which
will be treated separately later.
2-1
CONVERSION FROM ZULU
TIME TO LOCAL TIME
The conversion from ZULU time to local
time is the reverse procedure of local to ZULU.
For example, you are in San Diego, California,
and receive a message from Washington, D.C.,
with a DTG of 101800Z. If you want the
Washington local time of message origination,
you need to know the zone designations for
WashingtonROMEO +5. Then, apply the
formula. Change the sign from +5 to -5 and
subtract the 5 hours from the ZULU time of
the message:
101800Z (ZULU DTG)
- 5 (Washington zone with "+"
reversed)
101300R (local DTG)
RULE: FROM ZULU TO LOCAL
REVERSE THE SIGN.
To check ourselves, lets work another
example of converting ZULU to local. The
U.S. Ambassador to Japan has received a
message from the U.S. Secretary of State
concerning the latters plans to visit Tokyo.
The Secretary has indicated an arrival time of
210830Z. The Ambassadors problem is one of
diplomacy: Should he arrange a luncheon or
an evening meal for the arrival of the
distinguished guest? We need not concern
ourselves with the geographic location of the
Secretary of State because he used ZULU time.
However, we must know the location and
designators for TokyoINDIA (-9). Armed
with this knowledge, apply the formula. We
reverse the local sign (change the -9 to a +9),
and work the math:
210830Z (ZULU arrival time)
+ 9 (local zone with "-" reversed)
211730I (local arrival time)
Forget the soup and sandwiches, hell be there
for supper!
NOTE: You may see some commercially
produced time zone charts with the
numerical zone designators reversed
("+" for the eastern hemisphere and
"-" for the western hemisphere).
Don t l et t hi s conf us e you.
Remember, in the eastern hemisphere
the time will always be later than
ZULU and in the western hemisphere
it will always be earlier than ZULU.
COMPUTING TIME IN
GEOGRAPHIC POSITIONS
Coordinates is a general term for numbers
representing the degrees, minutes, and seconds
of a geographic position. The correlation of
time and geographic coordinates is a critical
skill for members of the intelligence
community. Once you have learned to convert
time from local to ZULU and from ZULU to
local, the conversion using positional
coordinates is a simple matter.
Lets consider a typical position report. A
position report is normally sent as two sets of
numbers. The first set of numbers is the
latitude (north or south). The second set of
numbers is the longitude (east or west) and is
the set that we use in time conversion.
Normally, the longitude of a position report
(the second set of numbers) is sent as a
five-digit group. The first three digits of this
group indicate the geographical degrees; the
last two are the minutes. The group is followed
immediately by an "E" (east) or a "W" (west) to
indicate the hemisphere. For example,
11530W indicates the location is 115 degrees
and 30 minutes west of the prime meridian.
There are 180 of longitude to the west of
Greenwich and 180 longitude to the east
(180W longitude and 180E longitude =
International Date Linethe 180th meridian).
Each degree can be broken into 60 minutes.
As stated above, the five-digit longitude is
normal; however, sometimes you will encounter
a seven-digit longitude. This is simply a further
2-2
breakdown of the minutes into seconds. One
minute contains 60 seconds. When this occurs,
the first three digits indicate degrees; the next
two digits indicate minutes; and the last two
digits indicate seconds. In any event, the
longitude of a position will place the target into
a specific time zone.
To determine this zone, well use a
hypothetical position report sent in chatter:
1235N 07242W. We may disregard the first
set of numbers (latitude) and concern ourselves
only with the second set of numbers (longi-
tude). The "072" represents the number of
degrees of longitude from the prime meridian
(Greenwich) and the "42" is the number of
geographical minutes from the 072 degree line
(72nd meridian). The "W" tells us that the
target is located to the west of the prime
meridian, in the western hemisphere.
NOTE: Remember, a time zone spans 15 of
longitude, with the ZULU zone
divided into 7 of longitude east and
7 of longitude west of the prime
meridian.
The first step in our computation is to
draw a graphic chart showing the western half
of the ZULU time zone. Now, label the
western border of the ZULU time zone (7
west longitude, or 00730W). We must now
continue our chart, proceeding outward from
ZULU, labeling the western borders of each of
the time zones until we reach a point where the
hypothetical longitude is equaled or exceeded.
For example, the western border of zone
NOVEMBER is 02230W (00730 + 15);
OSCAR is 03730W;
PAPA is 05230W;
QUEBEC is 06730W; and
ROMEO is 08230W.
Once we reach the fast meridian to exceed
the longitude (in this case, ROMEO zones
western border is the first of the western
borders to exceed our longitude of 07242W),
we need go no further with our labeling. See
figure 1-1. Longitude 07242W falls to the
west of zone QUEBEC, but not past zone
ROMEO. Our longitude falls within the
ROMEO zone, or zone +5.
Aft er det ermi ni ng t he t i me-zone
designation for our target, we apply or reverse
the sign, depending upon whether we want to
determine the ZULU time from local time, or
the local time from ZULU time. Longitudes in
the eastern hemisphere are handled in the same
way, except that the eastern borders are used
instead of the western borders.
Lets look at another example. This time
we will establish the targets time-zone
designators (its longitudinal parameters). An
unlocated ship sends its local time as 0945.
Your local time is 1345B. The first step in
solving this problem is to convert your local
time to ZULU. Use the formula, FROM
LOCAL TO ZULUAPPLY THE SIGN.
All you have to do is subtract your time zone
from your local time to arrive at ZULU. Zone
BRAVO is -2. By subtracting the local time
zone of -2 from your local time of 1345B, you
arrive at ZULU time1145Z. Since it has
been established that it is 1145Z, and the target
operator has given his local time as 0945, all
you need to do is subtract the smaller figure
from the larger. The difference will equate to
the time zone of the target.
1145
-0945
0200 (or +2 time zone)
After all, if it is 1145Z in BRAVO zone, it must
also be 1145Z in OSCAR and in all other
zones.
2-3
COMPUTATIONS INVOLVING
THE INTERNATIONAL
DATE LINE
In our discussions of the International
Date Line, we covered two very important
points which bear repeating:
1. It is always the same time in zone
MIKE as it is in zone YANKEEit is never
the same day.
2. When you cross the International
Date Line, apply the sign of the departed
hemisphere to determine whether to add or to
subtract a day. Keep in mind that whenever we
cross the line, the day must change.
To i l l ust r at e t he ef f ect t hat t he
International Date Line has upon a DTG, lets
assume that we are flying from Tokyo to San
Francisco. We begin by listing the facts that
we must know about each place:
1. The t i me zone desi gnat or s of
TokyoINDIA (-9).
2. The time zone designators of San
FranciscoUNIFORM (+8).
3. The date and time of departure from
Tokyo20 April, at 0800I.
4. The flying time is 13 hours.
THE PROBLEM: What will be the local time
and date when we land in
San Francisco?
To solve this problem, make a graphic
chart showing each of the time zones between
Tokyo and San Francisco, labeling each zone
with its designators. See figure 1-1. (Dont
forget to label the International Date Line.)
Using our roughly drawn chart, lets fill in the
times between Tokyo (-9) and the Date Line.
Since we are moving in an easterly direction
we add 1 hour upon entering each new time
zone.
We have now reached the International
Date Line and find that, before crossing the
line, the local time is 201100M. We cross the
line, departing - 12 and entering + 12. Using
our formula for crossing the International Date
Line, we apply the sign of the departed
hemisphere and subtract 1 dayit is now the
19th of April. As stated before, the hour will
remain the same in YANKEE (1100Y) as it
was when we departed MIKEonly the day
changes.
Now lets leave YANKEE and continue
adding 1 hour for each new zone. Remember,
it is now the 19th, NOT the 20th, as it was
when we left Japan.
As we arrive in San Franciscos time zone
(UNIFORM), the local time is 191500U.
However, this is NOT the answer we are
seeking. All we have determined thus far is
that when it is the 20th of April at 0800 local
time in Tokyo, it is the 19th of April at 1500
local time in San Francisco. We are not
finished with the problem until we have added
the flying time to the local time in San
Francisco. By adding the 13 hours flying time,
we find that our arrival time in San Francisco
should be 200400U.
COMPUTATIONS INVOLVING
DAYLIGHT SAVING TIME (DST)
In computing time conversions, you will
frequently encounter problems where one or
both of the zones are using DST. Since the
purpose of this time modification is to extend
the daylight hours (primarily in the summer
months), all we have to do is to understand
what is done to establish this time.
DST is simply the setting of the clocks in
a particular area ahead 1 hour, thus extending
the onset of darkness by that margin.
Whenever we encounter a problem involving
DST, we work the problem according to the
methods outlined above, then subtract 1 hour.
This will give us the normal time for that zone.
If we are asked to solve a time-conversion
problem for a time zone using normal time and
instructed to give the answer in DST, we work
2-4
the problem and add 1 hour to obtain the time
in DST.
TIME-CONVERSION
WORKING AIDS
Most of us have seen charts or maps of the
world showing time zones. These are handy
tools to have when computing time. Obvi-
ously, we cant be expected to carry charts or
maps around in our back pocket everywhere we
go. The Navy has a 4" 6" working aid, the
time-conversion table. It is small enough to
carry in your wallet and is readily available at
most field stations. Also, there are many
commercially produced materials. Some of
these are better than others.
TIME-CONVERSION TABLE
The time-conversion table has 24
horizontal rows depicting the 24 hours of the
day, and 25 vertical columns showing the 25
time zone designators. See table 2-1. Notice
that zones MIKE and YANKEE are identical,
with the exception of the day.
To use the time-conversion table, find the
zones in question along the horizontal row at
the bottom of the table and go up the vertical
column of the known time zone. Then find the
corresponding vertical position of the unknown
zone. You now have the time of the unknown
zone in relation to the known zone. Its as
simple as that.
COMMERCIAL TIME-
CONVERSION AIDS
The commercially produced time-
conversion aids, primarily designed to aid the
tourist, are inadequate for military and
communications use. They generally disregard
zone designators and the computation
processes. Figure 2-1 shows a typical
tourist-oriented, time-conversion aid and is
included in this manual only as an example of
these aids.
We have discussed time-conversion
working aids only to advise you that there are
shortcuts. There are no shortcuts to
professionalism, however, and each of the
time-conversion aids has its shortcomings. Did
you notice that the time-conversion table is of
no help in establishing positional locations of
targets? Additionally, if you are on a direct-
support platform, or at an isolated duty station
where the time conversion table is not
available, the success of your mission might
well depend upon your ability to compute time.
TOPIC SUMMARY
If any one of these areas is unclear to
you, go back to the discussion and master
that procedure.
1. To determine ZULU time from local
time, apply the sign ("+" or "-") and add or
subtract the numerical designator to or from
the local times hours.
2. To determine local time from ZULU
time, reverse the sign ("+" or "-") and add or
subtract the new numerical designator to or
from the ZULU times hours.
3. In problems involving geographical
positions:
a. Latitude is irrelevant for figuring
time; use only the longitude.
b. Use all five digits of the longitude
(seven digits, if given).
c. Proceed in an easterly or westerly
direction from the prime meridian, according
to the "E" or "W" designation.
d. Make a rough, graphic chart to
establish the zone in which a given longitude
falls.
( 1) Ent er t he l ongi t udi nal
coordinates for the ZULU zone (00730E or
00730W).
2-5
P
a
g
e

2
-
6
.
T
a
b
l
e

2
-
1
.

T
i
m
e
-
C
o
n
v
e
r
s
i
o
n

T
a
b
l
e
Figure 2-1.Typical commercial time-conversion
aid.
(2) When traveling from the
eastern or western border of zone ZULU, add
15 for each new zone; place this new
longitudinal coordinate at the eastern or
western meridian of the zone, as required.
e. Solve the time problem like any
other problem after placing the target into the
zone corresponding to its longitudinal
coordinates.
4. In problems involving the use of a
targets local time to establish its longitudinal
parameters:
a. Convert your local time to ZULU.
b. Work from ZULU time to derive
the local time of the target.
c. Pl ace t he t arget wi t hi n i t s
geographic zone once the local time is
determined.
5 . I n p r o b l e ms i n v o l v i n g t h e
International Date Line:
a. Separate the MIKE and YANKEE
zones.
b. Label both "+" and "-" designators
(MIKE is "-"; YANKEE is "+").
c. It is always the same time in MIKE
as it is in YANKEE, but never the same day.
d. The day must change each time the
International Date Line is crossed.
e. Apply the sign of the departed
hemisphere when crossing the line to determine
whether to add or to subtract a day.
6. In problems involving daylight saving
time (DST):
a. When time is given in DST, work
the problem in normal fashion, then subtract 1
hour to arrive at the zones normal time.
b. When the zones normal time is
given, work the problem in the usual fashion,
then add 1 hour to determine DST.
REFERENCES
Communications Instructions General, ACP
121(F), Annex A, Joint Chiefs of Staff,
Washington, DC, 15 April 1983.
2-7
TOPIC 3
GEOGRAPHY AND PLOTTING
To gain a greater knowledge of time
theory and time conversion computations, we
must have a complete understanding of the
Earth, upon which we navigate and travel.
Reference points for locating objects on
the Earth have been established by general
agreement among maritime nations. The
North and South poles are at the ends of the
axis on which the Earth rotates. Imaginary
lines (an infinite number of them) running
through the poles and around the Earth are
called meridians. They divide the Earth into
sections. The Equator is an imaginary line
around the Earth that bisects every meridian
and divides the Earth in half: the Northern
Hemisphere and the Southern Hemisphere.
Meridians and the Equator are called great
circles because they each divide the world into
halves. Any circle drawn around the Earth so
as to divide it into equal parts is called a great
circle.
Measurement along a meridian is ex-
pressed in degrees, minutes, and seconds of arc.
Each degree contains 60 minutes (); each
minute, in turn, contains 60 seconds ().
MERIDIANS
For every degree around the Earth, there
is a meridian. There are 360 of them 60, or
3600, apart. The starting point for number-
ing meridians is the one passing through the
Royal Observatory at Greenwich, England.
Figure 3-1.Meridians and parallel
The Greenwich meridian is number 0.
Meridians run east and west from 0 to the
180th meridian on the opposite side of the
Earth. The complete circle formed by the 0
and the 180th meridians, like the Equator,
divides the Earth into two exact halves: the
East ern Hemi sphere and t he West ern
Hemisphere. Every meridian runs true north
and south.
PARALLELS
We need a second set of imaginary lines to
complete our coordinate system. These lines
are formed by planes that are parallel to the
plane passing through the Earth at the
Equator. The lines on the Earth resulting from
cutting it with these parallel planes are circles
called parallels. The starting point for
numbering these parallels is the Equator. They
are numbered from 0 to 90 north and south of
the Equator. The system is shown in figure 3-1.
3-1
Figure 3-2.Measuring parallels of latitude.
GEOGRAPHIC COORDINATES
You must use the concepts of direction
and distance to locate points. Primitive man
probably did this in relative terms, using aids
such as the directions of the rising and setting
sun, forward and backward, and left and right.
He probably expressed distance in terms of
travel time in relation to his own location. A
universal system, however, must have some
unique reference or starting point. If we
designate such a point, then we can state the
location of every other point in terms of
direction and distance from it. The most
widely accepted system of locating a point on
the Earths surface uses lines of latitude and
longitude known as geographic coordinates.
Coordinates allow us to provide an answer to
the question "Where is it?"
LATITUDE
When you draw a grid on a globe, you
must have a starting point. Unlike drawing a
grid on a piece of paper where you can start in
a corner or at the center, drawing a grid on a
globe requires that you have a starting point
that everybody accepts. The point of origin for
latitude is the Equator. The Equator is an
Figure 3-3.Degrees, minutes, and seconds.
imaginary line, with a numerical value of 0,
running east and west around the center of the
Earth.
Latitude locates a place relative to the
Equator. Because the numbering of lines of
latitude begins with 0 at the Equator and
increases towards the poles, we must show
whether the latitude of a place is north or south
of the Equator.
The value of a line of latitude is
determined by the angle formed by drawing a
line from the Equator to the center of the
Earth, and then back out to the surface of the
Earth. See figure 3-2. Since the value of any
angle would be constant all the way around the
Earth, a line drawn on the Earths surface
connecting all the points that are formed by the
angle would be parallel to the Equator. For
this reason, latitude is commonly referred to as
a parallel of latitude. Since 90 is straight up or
down in relation to the Equator, the North and
South poles are 90. Therefore, you have
latitude running from 0 to 89 north or south
of the Equator.
Each degree is subdivided into minutes().
For instance, between 48 and 49 north
latitude, there are 60 minutes. If you were
locating a point that was halfway between 48
and 49 north latitude, it would be at 48
3-2
degrees, 30 minutes north (4830N). See
figure 3-3. Each minute is subdivided into
seconds (). For instance, between 30 and
31) there are 60 seconds. So if you were
locating a point that was one-quarter of the
way between 30 and 31, it would be at 48
degrees, 30 minutes, 15 seconds north
(483015N). Again, see figure 3-3.
The military writes coordinates using a
system called military notation without the
symbols , , or . This system uses 6 numbers
plus a letter to indicate north or south. The
coordinate 483015N would be written
483015N. When a position has less than 10 of
latitude in its coordinate designation, a zero is
added to the left of the degree number. In
other words, latitude will have two digits.
Seven degrees of latitude appears as 07 in the
designation. Likewise, two digits designate
minutes and seconds: for example, 030704N
or 801708S.
NOTE: In geographic coordinates,
always write the latitude first.
LONGITUDE
The point of origin for the vertical lines
(longitude) on American and British maps is an
imaginary line running from the North Pole to
the South Pole through Greenwich, England.
Like the Equator, it has a numerical value of 0
degrees. It is called the Greenwich meridian or
the prime meridian. Many foreign maps do not
use this line as the zero reference. For example,
French maps use the Paris meridian, and
Italian maps use the Rome meridian. Data
from foreign maps must be examined to
determine the prime meridian in use.
Figure 3-4.Meridians of longitude.
All of the other lines of longitude are simply
called meridians. See figure 3-4.
Longitude measurements are relative to
the prime meridian. Because the numbering of
meridians begins with 0 at the prime meridian
and increases to both the east and the west, we
must show whether the longitude is east or west
of the prime meridian.
The prime meridian and the 180th The value of a meridian is determined by
meridian divide the Earth into two equal the angle formed by drawing a line from the
vertical partsthe Eastern Hemisphere to the
Equator, at the point where the prime meridian
right of the prime meridian and the Western crosses it, to the center of the Earth, and then
Hemisphere to the left of the prime meridian. back out to another point on the Equator. See
3-3
Figure 3-5.Measuring meridians.
figure 3-5. The angle formed by the
intersection of those two lines is the value
assigned to that meridian. In this way, the
angles are measured around the Earth in both
an east and a west direction until you reach
180. Since there are 180 on each half of the
globe, you have a circle of 360.
Each degree of longitude is subdivided
into minutes and seconds in the same manner
as latitude. However, remember two things
about longitude:
1. West longitude is measured from right
to left on a map; east longitude is measured
from left to right.
2. When you write longitude in military
notation, use seven numbers plus a letter to
indicate east or west. When a position has less
than 100 of longitude, a zero is added to the
left of the degree number; less than 10, two
zeros are added. For example: 0074321W for
7 degrees, 43 minutes, 21 seconds west.
DIRECTION
We usually indicate direction from true
north. We give directions in degrees, measured
clockwise from true north, or 000T. We state
courses and bearings in three digits. In other
words, 45 degrees is 045 (zero four five).
Seldom is it necessary to consider compass
direction to a value smaller than a degree, even
though each degree contains 60 minutes of 60
seconds each.
A true bearing is the direction of an object
from the observer, measured clockwise from
true north. A relative bearing is the direction
of an object measured clockwise from the ships
bow. Objects seen by lookouts are reported in
terms of relative bearings by degrees. See
figure 3-6.
The reciprocal a bearing is its opposite;
that is, the point or degree on the opposite side
of the compass from the bearing. For example,
the reciprocal of 180 is 000. When you obtain
a bearing on an object, the bearing from the
3-4
Figure 3-6.True and relative bearings.
object to you is the reciprocal of the bearing
from you to it. To fmd the reciprocal of any
bearing expressed in degrees less than 150,
simply add 180 to the bearing. If the bearing
is 050, its reciprocal is 050 plus 180 or 230.
If your bearing is greater than 180, subtract
180.
In addition to true and relative direction
measurement, there are other common
references, such as measurement from the
magnetic pole and grid reference lines on
charts. However, all direction measurement
systems are based on the degrees in a circle or
points on a compass rose.
The Cardinal Point System
For centuries, navigators used a system of
compass readings, called compass points, to
indicate direction. An observer would use the
cardinal points of the compass (north, south,
Figure 3-7.The mariners cardinal point system.
east, and west) and intervening points between
each cardinal point to indicate the direction of
an object. Figure 3-7 shows the 32 relative
bearings by points around a ship. The cardinal
point system may be used when a high degree
3-5
Figure 3-8.The mariners cardinal point system.
of accuracy is not required. Only the rules of
the road and some harbor pilots and coastal
merchant mariners still express direction in
points. Figure 3-8 shows a compass rose with
16 points of the compass.
The Azimuth System
The azimuth system measures direction by
dividing a circle into 360 equal parts, called
degrees, and subdividing each degree into
minutes and seconds. We measure direction in
degrees, minutes, and seconds clockwise from
north in a horizontal plane. Some marine
compasses show both the cardinal point and
the azimuth figures on their cards. Figure 3-9
shows a compass card with the azimuth system
and eight cardinal points superimposed on it.
In this figure, the subdivisions of a degree are
not shown. For most navigational purposes,
subdivisions of a degree are not necessary.
MAPS, CHARTS, AND
PROJECTIONS
To become knowledgeable in geography
and plotting, an understanding of maps, charts,
and projections is extremely helpful. We will
discuss these in the following paragraphs.
MAPS
A map is a graphic representation of
selected features of the Earths surface, drawn
to scale. A map is a compact data basean
information storage and retrieval systemthat
does not require machine action. Instead, the
skilled map reader retrieves information from
the map.
From another viewpoint, maps are two-
dimensional models of the Earth. Topographic
maps are three-dimensional models that show
elevation by using contour lines.
3-6
Figure 3-9.Compass card.
The graphic representations on maps may
consist of
lines and symbols of various colors;
depths and locations of navigational aids. An
air navigation chart may show land, but it
provides the air navigator with elevations as
well as the locations of navigational aids.
drawings of landforms, called physio-
graphic diagrams; or
photographs with the addition of lines
and colors to emphasize features.
CHARTS
A chart is a special-purpose map, gener-
ally designed for a form of navigation, such as
air navigation. There is a difference between
charts and maps. Maps show land areas,
political subdivisions, and topography. A
chart details water areas and has reference
lines on it to allow the navigator to
graphically plot information. A hydrographic
chart provides information such as water
PROJECTIONS
A projection is a method of representing a
three-dimensional object on a two-dimensional
surface. Cartographers (map makers) use
projection techniques to build maps or charts;
however, it is impossible to project a three-
dimensional object upon a two-dimensional
surface without distortion. The type of
projection they use depends on the area to be
represented and the use of the map or chart.
Distortion cannot be avoided, but it can
be controlled. Map makers have created
several projections to represent the Earths
surface on a plane. In any projection, they
establish a network of lines corresponding to
geographic coordinates. This network of lines
3-7
Figure 3-10.A Mercator projection.
enables them to place each detail. To use a
chart effectively, we must understand the
purpose of the projection system and its good
and bad features.
The Mercator projection, the most
common method of making nautical charts,
was developed by a Flemish cartographer in the
sixteenth century. The Mercator chart is
projected by fast placing a cylinder around the
Earth, tangent at the Equator. Planes are
passed through the meridians and projected to
the cylinder upon which they appear as parallel
lines of longitude. Lines are drawn from the
center of the Earth to the cylinder passing
through the parallels to locate the lines of
latitude on the cylinder. Then, the cylinder is
cut lengthwise and flattened. See figure 3-10.
Figure 3-11.The difference between a great circle
and a rhumb line on the Earths surface.
3-8
Figure 3-12.Mediterranean Sea.
The resulting horizontal and vertical lines
form a simple Mercator projection. In the
production of todays Mercator charts,
parallels are spaced by mathematical formulae.
The advantage of a Mercator projection is that
it is a conformal chart, showing true angles and
true distance. A rhumb line (a line that makes
the same angle with all intersected meridians)
plots as a straight line on a Mercator chart.
See figure 3-11. On a Mercator chart,
meridians are parallel. A disadvantage of a
Mercator chart is the distortion at high
latitudes. At the poles, meridians actually
converge; however, they are parallel on the
chart. Greenland, in the higher latitudes on a
Mercator chart, appears larger than the
United States, although it is much smaller.
Even in the high latitudes though, the
distortion on a Mercator projection does not
prevent the measurement of true distance.
AREAS OF INTEREST
We will conclude with a brief discussion
of some of the more important U.S. Navy
operating areas. These include the Mediter-
ranean Sea, the Middle East/Persian Gulf area,
and the Western Pacific.
MEDITERRANEAN SEA
The nearly landlocked Mediterranean Sea
has been an influential factor in world affairs
throughout history. The Navys Sixth Fleet
operates from the Strait of Gibraltar at the
western end of the Mediterranean, to the shores
of Israel, Lebanon, and Syria at the eastern
end. See figure 3-12. The Strait of Gibraltar is
a vital choke point between the Mediterranean
and the Atlantic Ocean, as is the Suez Canal,
which provides access from the Mediterranean
to the Red Sea and the Indian Ocean beyond.
MIDDLE EAST/PERSIAN GULF
The U.S. Navy has significantly increased
its role in this volatile area. The Commander,
Joint Task Force Middle East, located at
Bahrain, is augmented by ships of both the
Atlantic and Pacific Fleets. Atlantic Fleet ships
enter the Red Sea via the Suez Canal and then
proceed through the Gulf of Aden to the North
3-9
P
a
g
e

3
-
1
0
.
F
i
g
u
r
e

3
-
1
3
.

M
i
d
d
l
e

E
a
s
t
.
Figure 3-14.Western Pacific.
Arabian Sea/Gulf of Oman. To enter the
Persian Gulf (also referred to as the Arabian
Gulf), ships must navigate another strategic
choke point, the Strait of Hormuz. See figure
3-13.
WESTERN PACIFIC
The U.S. Seventh Fleet, headquartered
in Yokosuka, Japan, is responsible for this
large area. See figure 3-14. A carrier
battle group is homeported in Yokosuka to
quickly respond to any regional tensions. Our
naval presence in the Southeast Asia area is
changed somewhat now with the loss of our
base in Subic Bay, Republ i c of t he
Philippines. Many of those support activities
have relocated to Guam. Continued presence
in the area is important to protect the Strait of
Malacca, the passage between the South China
3-11
Sea, and the Indian Ocean. Pacific Fleet
ships enroute to the Arabian Sea/Persian Gulf
transit this strait. It is also an important
commercial route. Most of the tankers carry-
ing Mideast oil pass through it on their way to
Pacific ports.
REFERENCE
Analysis and ReportingAnalysis Tools,
NSGTP 683-14-44-90, Naval Education
and Training Program Management Sup-
port Activity, Pensacola, Florida, 1990.
3-12
A
Azimuth system, 3-6
C
Cardinal point system, 3-5 to 3-6
Charts, 3-7
Commercial time-conversion aids, 2-5
Computations involving daylight saving time
(DST), 2-4 to 2-5
Computations involving the International
Date Line, 2-4
Computing time in geographic positions, 2-2
to 2-3
Conversion from local time to ZULU time,
2-1
Conversion from ZULU time to local time,
2-2
D
Daylight saving time (DST), computations
involving, 2-4 to 2-5
Designators "+" and "-", 1-2
E
Expression of time, 1-4
G
Geographic positions, computing time in, 2-2
to 2-3
Geography and plotting, 3-1 to 3-12
azimuth system, 3-6
cardinal point system, 3-5 to 3-6
Geography and plottingContinued
charts, 3-7
direction, 3-4 to 3-6
geographic coordinates, 3-2
latitude, 3-2 to 3-3
longitude, 3-3 to 3-4
maps, 3-6 to 3-7
Mediterranean Sea, 3-9
meridians, 3-1
Middle East/Persian Gulf, 3-9 to 3-11
parallels, 3-1
projections, 3-7 to 3-9
Western Pacific, 3-11 to 3-12
Greenwich mean time (GMT), 1-1 to 1-5
expression of time, 1-4
global division and designators, 1-1 to 1-2
International Date Line, 1-4 to 1-5
physical characteristics of time zones, 1-1
to 1-4
zone-to-zone progression, 1-5
I
International Date Line, 1-4 to 1-5,2-4
L
Latitude, 3-2 to 3-3
Literal (letter) designators, 1-2
Local time to ZULU time, conversion from,
2-1
Longitude, 3-3 to 3-4
M
Maps, 3-6 to 3-7
Mediterranean Sea, 3-9
INDEX- 1
INDEX
Mercator projection, 3-8 to 3-9
Meridians, 3-1
Middle East/Persian Gulf, 3-9 to 3-11
N
Numerical designators, 1-2
P
Parallels, 3-1
Physical characteristics of time zones, 1-2 to
1-4
T
Time-conversion computation, 2-1 to 2-7
commercial time-conversion aids, 2-5
computations involving daylight saving
time (DST), 2-4 to 2-5
computations involving the International
Date Line, 2-4
computing time in geographic positions,
2-2 to 2-3
Time-conversion computationContinued
conversion from local time to ZULU time,
2-1
conversion from ZULU time to local time,
2-2
time-conversion table, 2-5
Time theory, 1-1 to 1-6
expression of time, 1-4
global division and designators, 1-1 to 1-2
Greenwich mean time (GMT), 1-1 to 1-5
International Date Line, 1-4 to 1-5
physical characteristics of time zones, 1-2
to 1-4
zone-to-zone progression, 1-5
W
Western Pacific, 3-11 to 3-12
Z
Zone-to-zone progression, 1-5
ZULU time to local time, conversion from,
2-2
INDEX-2
Assignment Questions
Information: The text pages that you are to study are
provided at the beginning of the assignment questions.
ASSIGNMENT 1
Textbook Assignment: Cryptologic Technician Training Series, Time Conversion, A95-23-00-92,
Topics 1, 2, and 3.
Learning Objective: Recognize concepts of 1-5. At the equator, each degree of longitude
time zone theory and time computation. spans how many nautical miles?
1-1. What is another name for the 180th
meridian?
1. Equator
2. Prime Meridian
3. Greenwich Meridian
4. International Date Line
1. 60
2. 150
3. 600
4. 900
1-6. What letter combination is correct in the
statement that follows?
1-2. Except for time zones MIKE and
YANKEE, how many degrees of
longitude span each time zone?
Time zones in east longitude are
A B
designated (plus) (minus) and must
1. 12
2. 15
3. 18
4. 25
C D
be (added to) (subtracted from) local
time to obtain Greenwich mean time.
1-3. Time zone designations use 25 of the 26
letters of the English alphabet. What
letter is NOT used?
1. A; C
2. A; D
3. B; C
4. B; D
1. A
2. J
3. Q
4. X
1-7. A message originated at 191045S should
be assigned what ZULU DTG?
1-4. In time zone problems, the ZULU time
zone (0) has a "+" designator.
1. 190445Z
2. 190545Z
3. 191545Z
4. 191645Z
1. True
2. False
1
1-8. When you cross the International Date
Line from the eastern hemisphere into the
western hemisphere, you always subtract
a day.
1. True
2. False
1-9. It is always the same time, but never the
same day, in time zones NOVEMBER
and YANKEE.
1. True
2. False
1-10. At the equator, what is the approximate
width, in nautical miles, of a time zone?
1. 500
2. 900
3. 1500
4. 1800
1-11. When the local time in Tokyo, Japan, is
210600I, what is the local DTG in
Pensacola, Florida (time zone SIERRA)?
1. 201500
2. 201600
3. 212000
4. 212100
1-12. Washington, D.C. (39N 077W) is in what
lettered time zone?
1. QUEBEC
2. SIERRA
3. ROMEO
4. UNFORM
1-13. What is the local DTG in zone PAPA at
1700A?
1. 1300
2. 1400
3. 2000
4. 2100
1-14. What is the local DTG in zone DELTA
when it is 032200Q?
1. 040600
2. 042200
3. 030600
4. 031400
1-15. The ZULU time zone passes through
which of the following countries?
1. Finland
2. England
3. Australia
4. Commonwealth of Independent States
(former Soviet Union)
1-16. What letter combination is correct in the
statement that follows?
The continental United States
(CONUS) spans four time zones
which are designated zones
A B
(E through H) (R through U)
C
and are numbered (+5 through +8)
D
(-5 through -8).
1. A; C
2. A; D
3. B; C
4. B; D
1-17. If it is 1500U on 30 September, what is
the local DTG in time zone MIKE?
1. 291900 SEP
2. 301100 SEP
3. 011000 OCT
4. 011100 OCT
2
1-18. It is 100500 local time in zone +2. What
will be the local DTG, 10 hours later, in
zone -4?
1. 092300
2. 101000
3. 101100
4. 102100
1-19. A ship at 3840N 11221E is in what time
zone?
1. +7
2. +8
3. -7
4. -8
1-20. When the time in Manila is 120600H,
what is the local DTG in Denver (time
zone TANGO)?
1. 111500
2. 131500
3. 122100
4. 112100
1-2 1. What is the local DTG at 14400E when it
is 0430 local time on 1 October at
17500W?
1. 300630
2. 010230
3. 020130
4. 020230
1-22. If it is 0300 local time on 31 May aboard
a ship in the North Atlantic (2200W),
what is the local DTG in Moscow (-3
time zone)?
1-23. It is 0500Z on 7 March. What is the local
DTG in Honolulu (2720N 15642W)?
1. 071500
2. 071400
3. 061900
4. 061800
1-24. A message transmitted at 051000I from
Tokyo is received in Washington, D.C.,
(3800N 07730W) one hour later. What is
the local DC DTG at the time of receipt?
1. 052300H
2. 060000H
3. 042000R
4. 042100R
1-25. Your ship is at 0105N 05000E. An
unidentified submarine has been located
at 0045N 06930E. Approximately how
many nautical miles is your ship from the
submarine?
1. 585
2. 975
3. 1170
4. 1950
1-26. A ship is at 0027N 04230W at 102300Z.
What is the local DTG aboard the ship?
1. 102000C
2. 102000P
3. 110200C
4. 110200P
1. 302300 MAY
2. 310700 MAY
3. 310800 MAY
4. 310700 JUN
3
MAYDAY.YPOS.T.ONIS34-5.N0.8-30.17/0415 ...DE... 0003N 1.505. 090 014 1705 K
FIGURE 1A FIGURE 1B
IN ANSWERING QUESTION 1-27,
REFER TO FIGURE 1A.
1-27. On 17 January at 0215Z, a radioman
aboard t he USS WHITE PLAINS
intercepted the garbled position report in
figure 1A from a vessel in distress.
Assuming the transmission time (0415)
reflects the local time at the vessels
position, what is the probable longitude?
1. 01830E
2. 02830E
3. 01830W
4. 02830W
1-28. A message originated in Moscow (-3
time zone) at 200625Z was received by a
ship in the +12 time zone at 211325Y.
How long was the message en route?
1. 1 hour and 25 minutes
2. 28 hours
3. 31 hours
4. 43 hours
1-29. An airplane departs Kennedy Airport
(N.Y.) at 1130 local time on 14 June for
Pakistan (time zone ECHO). If the flight
time is 14 hours and 17 minutes, what is
the local DTG when it arrives in
Pakistan?
1. 142047
2. 141747
3. 151147
4. 151447
YOU ARE ABOARD A COAST GUARD
CUTTER ON PATROL I N THE
PACIFIC. YOUR RADIOMAN HAS
JUST RECEIVED THE PARTIAL
POSITION REPORT IN FIGURE 1B
FROM AN UNIDENTIFIED VESSEL.
THE TIME OF RECEIPT IS 220706Z
AND THE POSI TI ON OF YOUR
CUTTER IS 0005N 17130W. USE THIS
INFORMATION AND FIGURE 1B TO
ANSWER QUESTIONS 1-30 THROUGH
1-32.
1-30. What was the local DTG aboard your
ship at the time the position report was
received?
1. 211406
2. 212006
3. 221406
4. 222006
1-31. Assuming the time of the position report
(1705) reflects the local time at the
unidentified vessels location, what is the
correct longitude?
1. 15505W
2. 15505E
3. 17505W
4. 17505E
1-32. The unidentified vessel is in what time
zone?
1. KILO
2. LIMA
3. XRAY
4. WHISKEY
4
1-33. You depart San Francisco by ship at
0857 local time on 28 June for Japan.
The time en route is 11 days, 12 hours
and 37 minutes. What is the local DTG
in Japan (time zone INDIA) when you
arrive?
1. 092134 JUL
2. 100634 JUL
3. 101434 JUL
4. 111434 JUL
1-34. A ship at 3500N 04520W is in what time
zone?
1. +3
2. +4
3. -3
4. -4
1-35. A missile launched at 0800Z on 1 May
impacts 35 minutes later at 3950N
17630E. What is the local DTG in the
target area at impact?
1. 301935 APR
2. 302035 APR
3. 011935 MAY
4. 012035 MAY
THE PRESIDENT OF THE UNITED STATES
HAS JUST SENT AN URGENT COMMUNI-
QUE FROM THE WHITE HOUSE TO THE
AMBASSADOR TO BRAZIL IN RIO DE
JANEIRO. THE DTG OF THE MESSAGE IS
212205Z. RIO DE JANEIRO IS SOUTH OF THE
EQUATOR IN TIME ZONE PAPA.
FIGURE 1C
IN ANSWERING QUESTIONS 1-36 AND
1-37, USE THE INFORMATION IN
FIGURE 1C.
1-36.
1-37.
1-38.
1-39.
What was the ZULU DTG in Rio de
Janeiro when the communique was
originated?
1. 220105
2. 220205
3. 211905
4. 212205
What was the local DTG in Washington,
D.C., when the message was originated?
1. 211705
2. 212005
3. 220305
4. 220705
You are onboard the USS CON-
STELLATION which is transiting the
Pacific east to west. Your current
position is 0027N 17820W. You receive
a report of an unidentified aircraft at
0030N 15540E. Approximately how
many nautical miles separate the carrier
from the unidentified aircraft?
1. 400
2. 720
3. 1560
4. 1880
When time is given in daylight saving
time, you add one hour to arrive at the
zones "normal" time.
1. True
2. False
5
1-40. Your parents are on vacation in Sydney,
Australia, (time zone KILO) and have
told you they will call you at 0630 on 1
June (Australia time). You are in San
Angelo, Texas, (time zone SIERRA)
and the CONUS is currently on daylight
saving time. At what local San Angelo
DTG will your parents call?
1. 311430 MAY
2. 311530 MAY
3. 010230 JUN
4. 012230 JUN
1-41. Assume that you are stationed in Hawaii
(time zone WHISKEY) and your de-
tailer told you to call on 30 June to check
on your next set of orders. At what local
DTG should you place your call to
contact your detailer on 30 June at 1500
local Washington, D.C. time?
1. 301000 JN
2. 302200 JN
3. 010100 JL
4. 011100 JL
1-42. At 1100Z, a French ship using zone
CHARLIE time sends a message to your
ship stating that their commanding
officer will be visiting your ship at 1500.
How much time does your ship have to
prepare for the VIP visit?
1. 1 hour
2. 2 hours
3. 3 hours
4. 4 hours
1-43. Assume you are planning a TAD trip to
Tokyo, Japan (time zone INDIA). You
are scheduled to depart Los Angeles,
California at 0800 local time on 30 April.
Your flight to Japan will take 10 hours.
What local DTG should you tell your
point of contact to meet you at Tokyos
International Airport?
1. 300100 APR
2. 291100 APR
3. 010100 MAY
4. 011100 MAY
1-44. If a missile was fired at 1316 local time on
4 February from a location in time zone
INDIA and the impact area had a
longitude of 17700E, what would be the
local DTG in the impact area when the
missile hits if the flight time is 16
minutes?
1. 041032Y
2. 041032M
3. 041632M
4. 041632Y
AS YOUR BATTLE GROUP PATROLS IN THE
PACIFIC AT 0015N 17015W AT 2245Z ON 30
APRIL, YOUR PICKET DESTROYER
LOCATES AN ENEMY AIRCRAFT CARRIER
AT 0026N 17145E.
FIGURE 1D
IN ANSWERING QUESTIONS 1-45
THROUGH 1-47, REFER TO FIGURE
1D.
6
1-45.
1-46.
1-47.
1-48.
1-49.
At the time the position of the enemy
carrier was obtained, what was the
approximate distance between it and
your battle group?
1. 620 NMs
2. 1080 NMs
3. 1440 NMs
4. 1880 NMs
What was the local DTG at the position
of the enemy carrier at 302245Z?
1. 300945 APR
2. 301245 APR
3. 010845 MAY
4. 010945 MAY
What was the local DTG at the position
of your battle group at 302245Z?
1. 301145 APR
2. 301245 APR
3. 011045 MAY
4. 010945 MAY
A Russian ship departs Vladivostock
(time zone -9) at 101327 local time and
arrives in Vancouver, B.C., (time zone
+8) exactly twelve days later. What was
the arrival time of the vessel?
1. 210600H
2. 212027U
3. 230600H
4. 232027U
At 0915Z on 22 December, the USS
LONG BEACH, located at 4130N
16845W, launched a surface-to-surface
missile. Forty-live minutes later, a
helicopter observed the splash-down of
the missile at 4045N 17015E. What was
the local DTG in the impact zone at the
time of splash-down?
1. 212100X
2. 222000L
3. 222100L
4. 230700M
Learning Objective: Identify geographic
reference and direction systems.
1-50.
1-51.
1-52.
1-53.
1-54.
Which of the following is a characteristic
of the prime meridian?
1. It passes through the Royal
Observatory at Greenwich, England
2. It runs true north and south
3. It divides the Eastern and Western
Hemispheres
4. Each of the above
Which of the following imaginary lines
is a parallel that divides the Earth in
half into Northern and Southern
Hemispheres?
1. The Prime Meridian
2. The Great Circle
3. The Equator
4. The 180th Meridian
The latitude of a given point locates that
point relative to its distance from the
equator.
1. True
2. False
In geographic coordinates, each degree is
divided into which of the following
subunits?
1. 30 minutes
2. 30 seconds
3. 60 minutes
4. 60 seconds
Which of the following designations
represents a point that is two-thirds of
the way from 35 north to 36 north
latitude?
1. 352000N
2. 352020N
3. 354000N
4. 354020N
7
1-55. A person traveled from Greenwich,
England, until reaching a meridian
designated 90. In which of the following
directions could the person have
traveled?
1. East only
2. West only
3. East or west
4. North
1-56. A relative bearing is the direction of an
object measured clockwise from which of
the following reference points?
1. The ships bow
2. Magnetic north
3. The object
4. True north
1-57. What is the reciprocal of 280?
1. 090
2. 100
3. 180
4. 200
1-58. A ship steaming at an azimuth of 315 is
headed in which of the following
directions?
1. Northwest
2. Southeast
3. Northeast
4. Southwest
Learning Objective: Recognize characteristics
of maps and charts.
1-59. Which of the following phrases defines a
chart?
1. A chart details land areas only
2. A chart is a map that is used only by
navigators of ships
3. A chart is the background upon which
a map, showing a portion of the
earths surface, is superimposed
4. A chart details water areas and is used
primarily for navigation
8
1-60. Map makers use which of the following
methods to represent three-dimensional
objects on a two-dimensional surface?
1. Hydrographics
2. Geographic coordinates
3. Topography
4. A projection
1-61. In the construction of a Mercator chart,
the surface of the Earth is projected upon
which of the following shapes?
1. A plane tangent to the Earth
2. A sphere tangent to the equator
3. A cylinder tangent to the equator
4. A cone tangent to the pole
1-62. Which of the following phrases describes
the appearance of meridians on a
Mercator projection?
1. Vertical lines that are parallel and
equally spaced
2. Parallel lines whose spacing increases
as longitude increases
3. Straight lines that intersect at the poles
4. Curved lines that bend toward the
point of tangency
1-63. Which of the following is a disadvantage
of a Mercator chart?
1. Distortion near the equator
2. Distortion at high latitudes
3. True distance cannot be measured
4. Parallel spacing is distorted
Learning Objective: Identify geographic areas
that hold interest to the Navy.
1-64. What is the choke point that a ship must
navigate to pass from the Atlantic Ocean
to the Mediterranean Sea?
1. Suez Canal
2. Strait of Hormuz
3. Strait of Malacca
4. Strait of Gibraltar
1-65.
1-66.
1-67.
1-68.
1-69.
What U.S. Navy fleet operates in the
Mediterranean Sea?
1. Second
2. Third
3. Sixth
4. Seventh
The island of Crete in the Mediterranean
Sea is located nearest to which of the
following coordinates?
1. 3125N 03015E
2. 3900N 00430E
3. 3500N 02500E
4. 3430N 03500E
A ship entering the Red Sea via the Suez
Canal will steer what approximate
heading to reach the Gulf of Aden?
1. SSE
2. ENE
3. S
4. SW
The eastern side of Saudi Arabia is
bordered by what body of water?
1. Arabian Sea
2. Red Sea
3. Gulf of Oman
4. Persian Gulf
Ships entering the Persian Gulf from the
Gulf of Oman must navigate what
strategic choke point?
1. Suez Canal
2. Strait of Hormuz
3. Strait of Malacca
4. Bab el Mandeb
1-70.
1-71.
1-72.
1-73.
1-74.
1-75.
Your ship is located at 1830N 05945E.
Which of the following countries is
closest to your location?
1. Oman
2. Saudi Arabia
3. Egypt
4. Iraq
What strategically important body of
water lies between Japan and Korea?
1. Pacific Ocean
2. Yellow Sea
3. Sea of Japan
4. South China Sea
What U.S. Navy fleet is responsible for
operations in the Western Pacific area?
1. Second
2. Third
3. Sixth
4. Seventh
A ship departing Guam on a heading of
350 is most likely destined for which of
the following countries?
1. Philippines
2. Indonesia
3. Japan
4. Taiwan
The Strait of Malacca is an important
passage between which of the following
two bodies of water?
1. Pacific Ocean and Sea of Japan
2. Pacific Ocean and South China Sea
3. South China Sea and Indian Ocean
4.
Indian Ocean and Coral Sea
Your ship is near 1800N 11200E on a
heading of 015. Which of the following
ports of call will you soon be visiting?
1. Manila, Philippines
2. Hong Kong
3. Tokyo, Japan
4. Jakarta, Indonesia
9