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DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. NONRESIDENT TRAINING COURSE October 1992 Time Conversion NAVEDTRA 14252

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Page 1: US Navy course - Time Conversion NAVEDTRA 14252

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

NONRESIDENTTRAININGCOURSE

October 1992

Time ConversionNAVEDTRA 14252

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

Although the words “he,” “him,” and“his” are used sparingly in this course toenhance communication, they are notintended to be gender driven or to affront ordiscriminate against anyone.

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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. Practicalexperience, schools, selected reading, and your desire to succeed are also necessary to successfully roundout a fully meaningful training program.

THE COURSE: This self-study course is organized into subject matter areas, each containing learningobjectives to help you determine what you should learn along with text and illustrations to help youunderstand the information. The subject matter reflects day-to-day requirements and experiences ofpersonnel 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 ornaval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classificationsand Occupational Standards, NAVPERS 18068.

THE QUESTIONS: The questions that appear in this course are designed to help you understand thematerial 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 arestudying and discover a reference in the text to another publication for further information, look it up.

1992 Edition Prepared byCTRCS Richard W. Piatt

Published byNAVAL EDUCATION AND TRAINING

PROFESSIONAL DEVELOPMENTAND TECHNOLOGY CENTER

NAVSUP Logistics Tracking Number0504-LP-026-8860

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Sailor’s Creed

“ I am a United States Sailor.

I will support and defend theConstitution of the United States ofAmerica and I will obey the ordersof those appointed over me.

I represent the fighting spirit of theNavy and those who have gonebefore me to defend freedom anddemocracy around the world.

I proudly serve my country’s Navycombat team with honor, courageand commitment.

I am committed to excellence andthe fair treatment of all.”

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CONTENTS

TOPIC PAGE

1. Time theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2. Time-Conversion Computation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

3. Geography and Plotting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1

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INSTRUCTIONS FOR TAKING THE COURSE

ASSIGNMENTS

The text pages that you are to study are listed atthe beginning of each assignment. Study thesepages carefully before attempting to answer thequestions. Pay close attention to tables andillustrations and read the learning objectives.The learning objectives state what you should beable to do after studying the material. Answeringthe questions correctly helps you accomplish theobjectives.

SELECTING YOUR ANSWERS

Read each question carefully, then select theBEST answer. You may refer freely to the text.The answers must be the result of your ownwork and decisions. You are prohibited fromreferring to or copying the answers of others andfrom giving answers to anyone else taking thecourse.

SUBMITTING YOUR ASSIGNMENTS

To have your assignments graded, you must beenrolled in the course with the NonresidentTraining Course Administration Branch at theNaval Education and Training ProfessionalDevelopment and Technology Center(NETPDTC). Following enrollment, there aretwo ways of having your assignments graded:(1) use the Internet to submit your assignmentsas you complete them, or (2) send all theassignments at one time by mail to NETPDTC.

Grading on the Internet: Advantages toInternet grading are:

• you may submit your answers as soon asyou complete an assignment, and

• you get your results faster; usually by thenext working day (approximately 24 hours).

In addition to receiving grade results for eachassignment, you will receive course completionconfirmation once you have completed all the

assignments. To submit your assignmentanswers via the Internet, go to:

http://courses.cnet.navy.mil

Grading by Mail: When you submit answersheets by mail, send all of your assignments atone time. Do NOT submit individual answersheets for grading. Mail all of your assignmentsin an envelope, which you either provideyourself or obtain from your nearest EducationalServices Officer (ESO). Submit answer sheetsto:

COMMANDING OFFICERNETPDTC N3316490 SAUFLEY FIELD ROADPENSACOLA FL 32559-5000

Answer Sheets: All courses include one“scannable” answer sheet for each assignment.These answer sheets are preprinted with yourSSN, name, assignment number, and coursenumber. Explanations for completing the answersheets are on the answer sheet.

Do not use answer sheet reproductions: Useonly the original answer sheets that weprovide—reproductions will not work with ourscanning equipment and cannot be processed.

Follow the instructions for marking youranswers on the answer sheet. Be sure that blocks1, 2, and 3 are filled in correctly. Thisinformation is necessary for your course to beproperly processed and for you to receive creditfor your work.

COMPLETION TIME

Courses must be completed within 12 monthsfrom the date of enrollment. This includes timerequired to resubmit failed assignments.

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PASS/FAIL ASSIGNMENT PROCEDURES

If your overall course score is 3.2 or higher, youwill pass the course and will not be required toresubmit assignments. Once your assignmentshave been graded you will receive coursecompletion confirmation.

If you receive less than a 3.2 on any assignmentand your overall course score is below 3.2, youwill be given the opportunity to resubmit failedassignments. You may resubmit failedassignments only once. Internet students willreceive notification when they have failed anassignment--they may then resubmit failedassignments on the web site. Internet studentsmay view and print results for failedassignments from the web site. Students whosubmit by mail will receive a failing result letterand a new answer sheet for resubmission of eachfailed assignment.

COMPLETION CONFIRMATION

After successfully completing this course, youwill receive a letter of completion.

ERRATA

Errata are used to correct minor errors or deleteobsolete information in a course. Errata mayalso be used to provide instructions to thestudent. If a course has an errata, it will beincluded as the first page(s) after the front cover.Errata for all courses can be accessed andviewed/downloaded at:

http:/ /www.advancement.cnet .navy.mil

STUDENT FEEDBACK QUESTIONS

We value your suggestions, questions, andcriticisms on our courses. If you would like tocommunicate with us regarding this course, weencourage you, if possible, to use e-mail. If youwrite or fax, please use a copy of the StudentComment form that follows this page.

For subject matter questions:E-mail: [email protected]: Comm: (850) 452-1688

DSN: 922-1688FAX: (850) 452-1370(Do not fax answer sheets.)

Address: COMMANDING OFFICERNETPDTC (CODE N316)6490 SAUFLEY FIELD ROADPENSACOLA FL 32509-5237

For enrollment, shipping, grading, orcompletion letter questions:E-mail: [email protected]: Toll Free: 877-264-8583

Comm: (850) 452-1511/1181/1859DSN: 922-1511/1181/1859FAX: (850) 452-1370(Do not fax answer sheets.)

Address: COMMANDING OFFICERNETPDTC (CODE N331)6490 SAUFLEY FIELD ROADPENSACOLA FL 32559-5000

NAVAL RESERVE RETIREMENT CREDIT

If you are a member of the Naval Reserve, youwill receive retirement points if you areauthorized to receive them under currentdirectives governing retirement of NavalReserve personnel. For Naval Reserveretirement, this course is evaluated at 2 points.(Refer to Administrative Procedures for NavalReservists on Inactive Duty, BUPERSINST1001.39, for more information about retirementpoints.)

COURSE OBJECTIVES

In completing this nonresident training course,you will demonstrate a knowledge of the subjectmatter by correctly answering questions on thefollowing:

• Concepts of time zone theory and timecomputation

• Geographic reference and directionsystems

• Characteristics of maps and charts• Geographic areas of interest to the Navy

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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 isrequested in processing your comments and in preparing a reply. This information will not be divulged withoutwritten authorization to anyone other than those within DOD for official use in determining performance.

NETPDTC 1550/41 (Rev 4-00)

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TOPIC 1

TIME THEORY

The development of high-speed trans-portation and communications has reduced therelative size of the earth to the extent thatpeople can now travel from North America toEurope in less than 3 hours; a message can besent from any place on the earth and arrive atany other place in seconds; and weapons ofevery description can be deployed fromsubsurface, surface, air, and space platforms.As this technology was emerging, it becameapparent that nations could no longer think interms of local times and conditions. Astandard time reference covering the entireworld was needed. Without a standard timesystem, a routine airline flight plan for aParis-to-San Francisco flight might read likethis:

Depart Paris—1200 Local TimeArrive London—1130 Greenwich

Mean TimeDepart London—1200 Greenwich

Mean TimeArrive New York—0950 Eastern

Standard TimeDepart New York—1050 Eastern

Standard TimeArrive Denver—0930 Mountain

Standard TimeDepart Denver—1000 Mountain

Standard TimeArrive San Francisco—0930 Pacific

Standard Time

In computing the elapsed time for theflight, or for any part of it, individualcalculations are necessary to adjust for time

zone changes. There also might be changes fordaylight saving time (DST) or other localdifferences. Time computations are easier if alltimes are computed on a common worldwidebasis. Then, our flight plan is simplified,looking like this:

Depart Paris—1100 GreenwichMean Time

Arrive London—1130 GreenwichMean Time

Depart London—1200 GreenwichMean Time

Arrive New York—1450 GreenwichMean Time

Depart New York—l550 GreenwichMean Time

Arrive Denver—1630 GreenwichMean Time

Depart Denver—1700 GreenwichMean Time

Arrive San Francisco—1730Greenwich Mean Time

GREENWICH MEAN TIME(GMT)

To meet the need for standardization, theinternational GMT system was developed. Allcountries of the world adopted its use.

GLOBAL DIVISION ANDDESIGNATORS

To compute time differences, you need tounderstand the international GMT system. In

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this system, the surface of the earth is dividedinto 24 zones, each extending through 15° oflongitude, with the initial zone lying betweenlongitudes 7½° east and 7½° west of the primemeridian. (Longitude is the name given to theimaginary lines that run lengthwise, north andsouth, between the North and South Poles.They have east and west designators.) The timesystem is named after Greenwich, England,because the zero meridian passes directlythrough that town. Each zone represents adifferent time in the 24-hour-day cycle, with a1-hour variation between each time zone. Tofurther aid in zone referencing, each time zonehas a numerical, a literal (letter) and, to aid inthe mathematical computation, a "+" or a "-"designator.

Numerical Designators

The zero meridian (prime meridian) is theimaginary line running down the center of theinitial time zone; thus, this time zone isdesignated "0" (zero) in the numbering system.The remaining zones are numbered consecu-tively, 1 through 12, both east and west of 7½°longitude, through 180° longitude. Thelongitudes of 180° east and 180° west are thesame imaginary line. This meridian is theInternational Date Line.

Let’s pause to consider what appears to bea contradiction. We stated that the earth isdivided into 24 time zones; however, we haveaccounted for 25 zones (12 east of zone 0, 12west of zone 0, and zone 0 itself, a total of 25zones). This contradiction will be resolvedlater in the discussion of the International DateLine and the requirement to have a point atwhich we shift from one day to another. Fornow, let’s agree there are only 24 time zones.

Literal (Letter) Designators

In addition to all zones having an assignednumber, each zone also has a letter designator.

The initial time zone, again because of itsdivision by the zero meridian, is designatedzone "Z" or ZULU. (Use the phonetic alpha-bet to pronounce the letters of the time zones.)

With 25 designators, we use every letter ofthe English alphabet except "J." See figure 1-1.Like the numbering system, the letters beginwith the ZULU (0) time zone and progress tothe east and west, consecutively. The zones tothe east of ZULU are lettered "A" through "M"(ALFA through MIKE) and the zones to thewest of ZULU are lettered "N" through "Y"(NOVEMBER through YANKEE). Re-member, beginning at ZULU and reading fromleft to right, we have zones ALFA throughMIKE (eastern hemisphere). Returning toZULU and reading from right to left, we findzones NOVEMBER through YANKEE (west-em hemisphere). Don’t forget to omit "J" inthe eastern hemisphere.

Designators "+" and "-"

Each zone has a designation of either "+"or "-" in addition to the numerical and literaldesignators. In time-conversion computations,you will see the reason for these designators.

Learning the "+" and "-" designationsystem is easy. All zones of the westernhemisphere have the designation "+." All zonesof the eastern hemisphere have the designation"-". see figure 1-1.

PHYSICAL CHARACTERISTICSOF TIME ZONES

With the exceptions of zones MIKE andYANKEE, which we will discuss later, eachtime zone spans 15° of longitude, with the 24principal meridians bisecting (dividing inhalf) each zone. At the equator, each degreeof longitude spans 60 nautical miles (NMs).Thus, a time zone spans 900 NMs (15 × 60 =900).

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NOTE: Remember, only at the equatoris each degree of longitude equal to 60 NMs.The natural curvature of the earth causes anarrowing of the zones as the north or southlatitude increases. The length of a degree oflongitude gets progressively smaller the fartherit is from the equator.

Time zones generally correspond with theprincipal meridians; however, sometimes theydeviate from their geographical meridians,especially on land areas. This is common alongcoastlines, in mountain ranges, and alongcountry borders. These deviations keep timeconstant wherever possible throughoutcountries, states, cities, and island chains.See figure 1-1.

EXPRESSION OF TIME

The U.S. military services, as well as mostforeign countries, use the international 24-hoursystem for expressing time. This method usesa four-digit group, with the first two digitsdenoting the hour, and the second two digitsindicating 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 is0001. The time designation 1327Z shows thatit is 27 minutes past 1:00 P.M., GMT.

To express the day of the month alongwith the time, we use a six-digit group. Thesesix digits are nothing more than a four-digittime, preceded by two digits indicating thedate. This six-digit group is a date-time group(DTG). The DTG 171327Z indicates the 17thday of the month at 1327Z.

The date element of the DTG always hastwo digits. This means the dates from the 1stthrough the 9th of the month must be precededby a zero (0) to meet this requirement (forexample, 011327Z, 021327Z, or 031327Z).Should a month other than the current one beintended, the standard abbreviation for themonth desired follows the DTG (for example,

011327Z JAN, 121327Z FEB, or 211327ZMAR).

In each of the above examples, the timeswere expressed in ZULU time. This is to makeyou think in terms of ZULU, since ZULU zonetime is the standard time for military com-munications . All messages, reports, andletters containing times, use ZULU time.This enables all mobile platforms and shorestations to know at what time the subject ofthe correspondence occurred. It becomessimply a matter of converting the ZULU timeof the occurrence to the local time.

Obviously, there are occasions when timemust be expressed as local. In these instances,the literal designator for the local zone is usedin exactly the same manner as the ZULUdesignator was used. For example, in theUNIFORM time zone, 171327U would indi-cate the 17th day of the current month, 27minutes past 1300 local time.

INTERNATIONAL DATE LINE

The International Date Line divides theeastern and western hemispheres. It is animaginary line located exactly 180° eastlongitude and 180° west longitude of the primemeridian. At this point, we must understandthe special circumstances surrounding zonesMIKE and YANKEE.

Each time zone has a numerical, a literal,and a "+" or a "-" designator, and zones MIKEand YANKEE are not exceptions. There is,however, a very important difference betweenzones MIKE and YANKEE and all other timezones. To understand this difference, look atzones MIKE and YANKEE as a single timezone of 15° of longitude, half (7½°) in theeastern hemisphere, and half in the westernhemisphere. Although the two halves of thiszone share a common number (12) each halfhas its own literal and "+" or "-" designator.The eastern hemisphere’s half is designatedMIKE -12; the western hemisphere’s half isYANKEE + 12.

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Now we come to a very important point inour discussion. Since we are considering theMIKE and YANKEE zones to be a singlezone, it follows that the time in MIKE isalways the same as that in YANKEE. This iswhere the International Date Line comes intoplay, for whenever this line is crossed, whetherfrom east to west or from west to east, the daymust change. Since we have already estab-lished that there is a 1-hour difference betweeneach of the 24 time zones, it is clear that thereis always a situation where it is a day earlier orlater in one part of the world than it is inanother.

RULE: IT IS ALWAYS THE SAMETIME IN ZONE MIKE AS ITIS IN ZONE YANKEE, BUTIT IS NEVER THE SAMEDAY.

A final point of discussion involving theInternational Date Line and zones MIKE andYANKEE is the "gaining" or "losing" of a dayas the line is crossed. This is not a problem."Gaining" or "losing" is nothing more than aquestion of semantics and should not be usedin time conversion conversation.

The formula for determining whether toadd or subtract one day from the current day atthe time of departing one hemisphereanother is:

When you cross the InternationalDate Line, apply the sign of thedeparted hemisphere. For example,to go from the MIKE zone into theYANKEE zone, subtract one day.MIKE is in the eastern (or the "-")hemisphere. To go from the YAN-KEE zone into the MIKE zone, addone 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 theline westbound and subtract a daywhen crossing eastbound.

for

ZONE-TO-ZONE PROGRESSION

At this point, we will discuss one morearea needed for time calculation. It isdirectional flow and the addition or subtractionof an hour when progressing from one timezone into another. Probably the best way toremember whether to add or to subtract thehour is to take the case of the four time zonesspanned by the United States (ROMEOthrough UNIFORM).

Most of us have, at some time or other,watched a sporting event being played on theWest Coast while we were physically located onthe East Coast. In cases where the contest washeld in the late afternoon or early evening inCalifornia, it was frequently dark in New York.Obviously, it was earlier in the day inCalifornia than it was in New York. There-fore, we can say with confidence that whenevertraveling from a westerly direction toward apoint eastward, we must add an hour each timewe pass from one time zone into another. Theopposite is also certainly true. When travelingfrom an easterly direction toward a pointwestward, we must subtract an hour for eachnew zone entered. This rule will hold trueregardless of your location in the world: westto east—add, east to west—subtract.Additionally, when the 0000 hour is reached,the day changes accordingly.

TOPIC SUMMARY

It is absolutely essential that youunderstand each of the points covered thus farin this manual before attempting to converttime. The following is a short review of theseprinciples. Test yourself. If you do not fullyunderstand any of them, go back and rereadthe related section.

1. The international Greenwich meantime (GMT) system was named for the town ofGreenwich, England, as the town is locateddirectly on the prime meridian, the point ofreference for the entire system.

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2. The surface of the earth is divided into24 time zones, each spanning 15° of longitude.

3. The initial zone is zone 0 (ZULU) andspans the area 7½° longitude east and 7½°longitude west of the prime meridian (a totalof 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 theeastern and western hemispheres.

7. The zones east of ZULU are letteredALFA through MIKE, omitting JULIETT,and each has a "-" designator.

8. The zones west of ZULU are letteredNOVEMBER through YANKEE, and eachhas a "+" designator.

9. At the equator there are 60 nauticalmiles (NMs) in a degree and each time zonespans 900 NMs; a time zone spans 15° ofl o n g i t u d e ( e x c e p t i o n : M I K E a n dYANKEE—each span 7½° of longitude).

10. The U.S. Navy uses the international24-hour time system, expressed in four digits;DTGs are formed by preceding the four-digit

time with a two-digit number expressing theday.

11. The International Date Line separatesthe designators MIKE and YANKEE (-12 and+12). The date will always change whencrossing this line, regardless of the direction ofcrossing. When you cross the line, apply thesign of the departed hemisphere.

12. MIKE and YANKEE are one timezone of 15° longitude, sharing the samenumerical designator (12). MIKE is the eastern7½° of longitude of this zone; YANKEE is thewestern 7½° of longitude.

13. The time will change by 1 hourwhenever a new time zone is entered: east towest, subtract 1 hour; west to east, add 1 hour.

14. The day changes to the next orprevious day once 0000 is reached, dependingupon the direction of travel.

15. The time is always the same in MIKEas it is in YANKEE, but it is never the sameday.

REFERENCES

Communications Instructions General, ACP121(F), Annex A, Joint Chiefs of Staff,Washington, DC, 15 April 1983.

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TOPIC 2

TIME-CONVERSION COMPUTATION

With U.S. naval ships and aircraftdeployed throughout the world, t imecomputation becomes a matter of concern tovirtually every naval member. Communicatorsuse ZULU time in messages and other recordcommunications. It is extremely importantthat you know how to make time conversionsfrom local to ZULU time and from ZULU tolocal time. Those involved in collection,processing and reporting, and traffic analysismust be able to make quick and accurate timeconversions throughout their working day.

CONVERSION FROM LOCALTIME TO ZULU TIME

We know the ZULU time zone has thenumerical designator zero (0). At this point,the "+" or "-" assigned to each of the otherzones comes into play. To convert the localtime to ZULU time, simply add or subtract asindicated by the sign (+ or -) of the local timezone.

For example, we are in Pensacola, Florida,and wish to assign a date-time group (DTG) toa message. We will have to use ZULU time forthe message. Pensacola is in the SIERRA timezone and is designated +6. The local date andtime is 191045S (the 19th of the month at 10:45A.M.). Since the SIERRA time zone is +6(Pensacola local time), add 6 to the local timeof 1045. Our answer is the conversion of191045S 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 placedunder the "hours" of the local DTG.

RULE: FROM LOCAL TIME TO ZULUTIME—APPLY THE SIGN.

To check ourselves for complete under-standing, let’s take one more example ofconverting local time to ZULU time. Thistime we are in Kamiseya, Japan, and wish toassign a DTG to an outgoing message. First,we have to know the zone designation forKamiseya—INDIA (-9). The date and time inKamiseya is 101800I. Using our formula, weapply 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 localtime to ZULU time from any place in theworld. The only variations that you willencounter involve the International Date Lineand daylight saving time (DST), each of whichwill be treated separately later.

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CONVERSION FROM ZULUTIME TO LOCAL TIME

The conversion from ZULU time to localtime 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 theWashington local time of message origination,you need to know the zone designations forWashington—ROMEO +5. Then, apply theformula. Change the sign from +5 to -5 andsubtract the 5 hours from the ZULU time ofthe message:

101800Z (ZULU DTG)- 5 (Washington zone with "+"

reversed)

101300R (local DTG)

RULE: FROM ZULU TO LOCAL—REVERSE THE SIGN.

To check ourselves, let’s work anotherexample of converting ZULU to local. TheU.S. Ambassador to Japan has received amessage from the U.S. Secretary of Stateconcerning the latter’s plans to visit Tokyo.The Secretary has indicated an arrival time of210830Z. The Ambassador’s problem is one ofdiplomacy: Should he arrange a luncheon oran evening meal for the arrival of thedistinguished guest? We need not concernourselves with the geographic location of theSecretary of State because he used ZULU time.However, we must know the location anddesignators for Tokyo—INDIA (-9). Armedwith this knowledge, apply the formula. Wereverse 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, he’ll be therefor supper!

NOTE: You may see some commerciallyproduced time zone charts with thenumerical zone designators reversed("+" for the eastern hemisphere and"-" for the western hemisphere).D o n ’ t l e t t h i s c o n f u s e y o u .Remember, in the eastern hemispherethe time will always be later thanZULU and in the western hemisphereit will always be earlier than ZULU.

COMPUTING TIME INGEOGRAPHIC POSITIONS

Coordinates is a general term for numbersrepresenting the degrees, minutes, and secondsof a geographic position. The correlation oftime and geographic coordinates is a criticalskill for members of the intelligencecommunity. Once you have learned to converttime from local to ZULU and from ZULU tolocal, the conversion using positionalcoordinates is a simple matter.

Let’s consider a typical position report. Aposition report is normally sent as two sets ofnumbers. The first set of numbers is thelatitude (north or south). The second set ofnumbers is the longitude (east or west) and isthe set that we use in time conversion.Normally, the longitude of a position report(the second set of numbers) is sent as afive-digit group. The first three digits of thisgroup indicate the geographical degrees; thelast two are the minutes. The group is followedimmediately by an "E" (east) or a "W" (west) toindicate the hemisphere. For example,115°30´W indicates the location is 115 degreesand 30 minutes west of the prime meridian.

There are 180° of longitude to the west ofGreenwich and 180° longitude to the east(180°W longitude and 180°E longitude =International Date Line—the 180th meridian).Each degree can be broken into 60 minutes.

As stated above, the five-digit longitude isnormal; however, sometimes you will encountera seven-digit longitude. This is simply a further

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breakdown of the minutes into seconds. Oneminute contains 60 seconds. When this occurs,the first three digits indicate degrees; the nexttwo digits indicate minutes; and the last twodigits indicate seconds. In any event, thelongitude of a position will place the target intoa specific time zone.

To determine this zone, we’ll use ahypothetical position report sent in chatter:12°35´N 072°42´W. We may disregard the firstset of numbers (latitude) and concern ourselvesonly with the second set of numbers (longi-tude). The "072°" represents the number ofdegrees of longitude from the prime meridian(Greenwich) and the "42´" is the number ofgeographical minutes from the 072 degree line(72nd meridian). The "W" tells us that thetarget is located to the west of the primemeridian, in the western hemisphere.

NOTE: Remember, a time zone spans 15° oflongitude, with the ZULU zonedivided into 7½° of longitude east and7½° of longitude west of the primemeridian.

The first step in our computation is todraw a graphic chart showing the western halfof the ZULU time zone. Now, label thewestern border of the ZULU time zone (7½°west longitude, or 007°30´W). We must nowcontinue our chart, proceeding outward fromZULU, labeling the western borders of each ofthe time zones until we reach a point where thehypothetical longitude is equaled or exceeded.

For example, the western border of zone

NOVEMBER is 022°30´W (007°30´ + 15°);

OSCAR is 037°30´W;

PAPA is 052°30´W;

QUEBEC is 067°30´W; and

ROMEO is 082°30´W.

Once we reach the fast meridian to exceedthe longitude (in this case, ROMEO zone’swestern border is the first of the westernborders to exceed our longitude of 072°42´W),we need go no further with our labeling. Seefigure 1-1. Longitude 072°42´W falls to thewest of zone QUEBEC, but not past zoneROMEO. Our longitude falls within theROMEO zone, or zone +5.

After determining the time-zonedesignation for our target, we apply or reversethe sign, depending upon whether we want todetermine the ZULU time from local time, orthe local time from ZULU time. Longitudes inthe eastern hemisphere are handled in the sameway, except that the eastern borders are usedinstead of the western borders.

Let’s look at another example. This timewe will establish the target’s time-zonedesignators (its longitudinal parameters). Anunlocated ship sends its local time as 0945.Your local time is 1345B. The first step insolving this problem is to convert your localtime to ZULU. Use the formula, FROMLOCAL TO ZULU—APPLY THE SIGN.All you have to do is subtract your time zonefrom your local time to arrive at ZULU. ZoneBRAVO is -2. By subtracting the local timezone of -2 from your local time of 1345B, youarrive at ZULU time—1145Z. Since it hasbeen established that it is 1145Z, and the targetoperator has given his local time as 0945, allyou need to do is subtract the smaller figurefrom the larger. The difference will equate tothe time zone of the target.

1145-0945

0200 (or +2 time zone)

After all, if it is 1145Z in BRAVO zone, it mustalso be 1145Z in OSCAR and in all otherzones.

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COMPUTATIONS INVOLVINGTHE INTERNATIONAL

DATE LINE

In our discussions of the InternationalDate Line, we covered two very importantpoints which bear repeating:

1. It is always the same time in zoneMIKE as it is in zone YANKEE—it is neverthe same day.

2. When you cross the InternationalDate Line, apply the sign of the departedhemisphere to determine whether to add or tosubtract a day. Keep in mind that whenever wecross the line, the day must change.

To i l lus t ra te the ef fec t tha t theInternational Date Line has upon a DTG, let’sassume that we are flying from Tokyo to SanFrancisco. We begin by listing the facts thatwe must know about each place:

1 . The t ime zone des ignators ofTokyo—INDIA (-9).

2. The time zone designators of SanFrancisco—UNIFORM (+8).

3. The date and time of departure fromTokyo—20 April, at 0800I.

4. The flying time is 13 hours.

THE PROBLEM: What will be the local timeand date when we land inSan Francisco?

To solve this problem, make a graphicchart showing each of the time zones betweenTokyo and San Francisco, labeling each zonewith its designators. See figure 1-1. (Don’tforget to label the International Date Line.)Using our roughly drawn chart, let’s fill in thetimes between Tokyo (-9) and the Date Line.Since we are moving in an easterly directionwe add 1 hour upon entering each new timezone.

We have now reached the InternationalDate Line and find that, before crossing theline, the local time is 201100M. We cross the

line, departing - 12 and entering + 12. Usingour formula for crossing the International DateLine, we apply the sign of the departedhemisphere and subtract 1 day—it is now the19th of April. As stated before, the hour willremain the same in YANKEE (1100Y) as itwas when we departed MIKE—only the daychanges.

Now let’s leave YANKEE and continueadding 1 hour for each new zone. Remember,it is now the 19th, NOT the 20th, as it waswhen we left Japan.

As we arrive in San Francisco’s time zone(UNIFORM), the local time is 191500U.However, this is NOT the answer we areseeking. All we have determined thus far isthat when it is the 20th of April at 0800 localtime in Tokyo, it is the 19th of April at 1500local time in San Francisco. We are notfinished with the problem until we have addedthe flying time to the local time in SanFrancisco. By adding the 13 hours flying time,we find that our arrival time in San Franciscoshould be 200400U.

COMPUTATIONS INVOLVINGDAYLIGHT SAVING TIME (DST)

In computing time conversions, you willfrequently encounter problems where one orboth of the zones are using DST. Since thepurpose of this time modification is to extendthe daylight hours (primarily in the summermonths), all we have to do is to understandwhat is done to establish this time.

DST is simply the setting of the clocks ina particular area ahead 1 hour, thus extendingthe onset of darkness by that margin.Whenever we encounter a problem involvingDST, we work the problem according to themethods outlined above, then subtract 1 hour.This will give us the normal time for that zone.If we are asked to solve a time-conversionproblem for a time zone using normal time andinstructed to give the answer in DST, we work

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the problem and add 1 hour to obtain the timein DST.

TIME-CONVERSIONWORKING AIDS

Most of us have seen charts or maps of theworld showing time zones. These are handytools to have when computing time. Obvi-ously, we can’t be expected to carry charts ormaps around in our back pocket everywhere wego. The Navy has a 4" × 6" working aid, thetime-conversion table. It is small enough tocarry in your wallet and is readily available atmost field stations. Also, there are manycommercially produced materials. Some ofthese are better than others.

TIME-CONVERSION TABLE

The time-conversion table has 24horizontal rows depicting the 24 hours of theday, and 25 vertical columns showing the 25time zone designators. See table 2-1. Noticethat zones MIKE and YANKEE are identical,with the exception of the day.

To use the time-conversion table, find thezones in question along the horizontal row atthe bottom of the table and go up the verticalcolumn of the known time zone. Then find thecorresponding vertical position of the unknownzone. You now have the time of the unknownzone in relation to the known zone. It’s assimple as that.

COMMERCIAL TIME-CONVERSION AIDS

The commercially produced time-conversion aids, primarily designed to aid thetourist, are inadequate for military andcommunications use. They generally disregardzone designators and the computationprocesses. Figure 2-1 shows a typical

tourist-oriented, time-conversion aid and isincluded in this manual only as an example ofthese aids.

We have discussed time-conversionworking aids only to advise you that there areshortcuts. There are no shortcuts toprofessionalism, however, and each of thetime-conversion aids has its shortcomings. Didyou notice that the time-conversion table is ofno help in establishing positional locations oftargets? Additionally, if you are on a direct-support platform, or at an isolated duty stationwhere the time conversion table is notavailable, the success of your mission mightwell depend upon your ability to compute time.

TOPIC SUMMARY

If any one of these areas is unclear toyou, go back to the discussion and masterthat procedure.

1. To determine ZULU time from localtime, apply the sign ("+" or "-") and add orsubtract the numerical designator to or fromthe local time’s hours.

2. To determine local time from ZULUtime, reverse the sign ("+" or "-") and add orsubtract the new numerical designator to orfrom the ZULU time’s hours.

3. In problems involving geographicalpositions:

a. Latitude is irrelevant for figuringtime; use only the longitude.

b. Use all five digits of the longitude(seven digits, if given).

c. Proceed in an easterly or westerlydirection from the prime meridian, accordingto the "E" or "W" designation.

d. Make a rough, graphic chart toestablish the zone in which a given longitudefalls.

(1) Enter the longi tudina lcoordinates for the ZULU zone (007°30´E or007°30´W).

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Pag

e 2-

6.

Tab

le

2-1.

—T

ime-

Con

vers

ion

T

able

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Figure 2-1.—Typical commercial time-conversionaid.

(2) When traveling from theeastern or western border of zone ZULU, add15° for each new zone; place this newlongitudinal coordinate at the eastern orwestern meridian of the zone, as required.

e. Solve the time problem like anyother problem after placing the target into thezone corresponding to its longitudinalcoordinates.

4. In problems involving the use of atarget’s local time to establish its longitudinalparameters:

a. Convert your local time to ZULU.

b. Work from ZULU time to derivethe local time of the target.

c. Place the target within itsgeographic zone once the local time isdetermined.

5 . I n p r o b l e m s i n v o l v i n g t h eInternational Date Line:

a. Separate the MIKE and YANKEEzones.

b. Label both "+" and "-" designators(MIKE is "-"; YANKEE is "+").

c. It is always the same time in MIKEas it is in YANKEE, but never the same day.

d. The day must change each time theInternational Date Line is crossed.

e. Apply the sign of the departedhemisphere when crossing the line to determinewhether to add or to subtract a day.

6. In problems involving daylight savingtime (DST):

a. When time is given in DST, workthe problem in normal fashion, then subtract 1hour to arrive at the zone’s normal time.

b. When the zone’s normal time isgiven, work the problem in the usual fashion,then add 1 hour to determine DST.

REFERENCES

Communications Instructions General, ACP121(F), Annex A, Joint Chiefs of Staff,Washington, DC, 15 April 1983.

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TOPIC 3

GEOGRAPHY AND PLOTTING

To gain a greater knowledge of timetheory and time conversion computations, wemust have a complete understanding of theEarth, upon which we navigate and travel.

Reference points for locating objects onthe Earth have been established by generalagreement among maritime nations. TheNorth and South poles are at the ends of theaxis on which the Earth rotates. Imaginarylines (an infinite number of them) runningthrough the poles and around the Earth arecalled meridians. They divide the Earth intosections. The Equator is an imaginary linearound the Earth that bisects every meridianand divides the Earth in half: the NorthernHemisphere and the Southern Hemisphere.Meridians and the Equator are called greatcircles because they each divide the world intohalves. Any circle drawn around the Earth soas to divide it into equal parts is called a greatcircle.

Measurement along a meridian is ex-pressed in degrees, minutes, and seconds of arc.Each degree contains 60 minutes (´); eachminute, in turn, contains 60 seconds (″) .

MERIDIANS

For every degree around the Earth, thereis a meridian. There are 360 of them 60´, or3600″, apart. The starting point for number-ing meridians is the one passing through theRoyal Observatory at Greenwich, England.

Figure 3-1.—Meridians and parallel

The Greenwich meridian is number 0.Meridians run east and west from 0 to the180th meridian on the opposite side of theEarth. The complete circle formed by the 0and the 180th meridians, like the Equator,divides the Earth into two exact halves: theEastern Hemisphere and the WesternHemisphere. Every meridian runs true northand south.

PARALLELS

We need a second set of imaginary lines tocomplete our coordinate system. These linesare formed by planes that are parallel to theplane passing through the Earth at theEquator. The lines on the Earth resulting fromcutting it with these parallel planes are circlescalled parallels. The starting point fornumbering these parallels is the Equator. Theyare numbered from 0 to 90 north and south ofthe Equator. The system is shown in figure 3-1.

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Figure 3-2.—Measuring parallels of latitude.

GEOGRAPHIC COORDINATES

You must use the concepts of directionand distance to locate points. Primitive manprobably did this in relative terms, using aidssuch as the directions of the rising and settingsun, forward and backward, and left and right.He probably expressed distance in terms oftravel time in relation to his own location. Auniversal system, however, must have someunique reference or starting point. If wedesignate such a point, then we can state thelocation of every other point in terms ofdirection and distance from it. The mostwidely accepted system of locating a point onthe Earth’s surface uses lines of latitude andlongitude known as geographic coordinates.Coordinates allow us to provide an answer tothe question "Where is it?"

LATITUDE

When you draw a grid on a globe, youmust have a starting point. Unlike drawing agrid on a piece of paper where you can start ina corner or at the center, drawing a grid on aglobe requires that you have a starting pointthat everybody accepts. The point of origin forlatitude 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 theEarth.

Latitude locates a place relative to theEquator. Because the numbering of lines oflatitude begins with 0 at the Equator andincreases towards the poles, we must showwhether the latitude of a place is north or southof the Equator.

The value of a line of latitude isdetermined by the angle formed by drawing aline from the Equator to the center of theEarth, and then back out to the surface of theEarth. See figure 3-2. Since the value of anyangle would be constant all the way around theEarth, a line drawn on the Earth’s surfaceconnecting all the points that are formed by theangle would be parallel to the Equator. Forthis reason, latitude is commonly referred to asa parallel of latitude. Since 90° is straight up ordown in relation to the Equator, the North andSouth poles are 90°. Therefore, you havelatitude running from 0° to 89° north or southof the Equator.

Each degree is subdivided into minutes(´).For instance, between 48° and 49° northlatitude, there are 60 minutes. If you werelocating a point that was halfway between 48°and 49° north latitude, it would be at 48

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degrees, 30 minutes north (48°30´N). Seefigure 3-3. Each minute is subdivided intoseconds (″). For instance, between 30´ and31´) there are 60 seconds. So if you werelocating a point that was one-quarter of theway between 30´ and 31´, it would be at 48degrees, 30 minutes, 15 seconds north(48°30´15″N). Again, see figure 3-3.

The military writes coordinates using asystem called military notation without thesymbols °, ´, or ″. This system uses 6 numbersplus a letter to indicate north or south. Thecoordinate 48°30´15″N would be written483015N. When a position has less than 10° oflatitude in its coordinate designation, a zero isadded to the left of the degree number. Inother words, latitude will have two digits.Seven degrees of latitude appears as 07 in thedesignation. Likewise, two digits designateminutes and seconds: for example, 030704Nor 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 animaginary line running from the North Pole tothe South Pole through Greenwich, England.Like the Equator, it has a numerical value of 0degrees. It is called the Greenwich meridian orthe prime meridian. Many foreign maps do notuse this line as the zero reference. For example,French maps use the Paris meridian, andItalian maps use the Rome meridian. Datafrom foreign maps must be examined todetermine the prime meridian in use.

Figure 3-4.—Meridians of longitude.

All of the other lines of longitude are simplycalled meridians. See figure 3-4.

Longitude measurements are relative tothe prime meridian. Because the numbering ofmeridians begins with 0° at the prime meridianand increases to both the east and the west, wemust show whether the longitude is east or westof the prime meridian.

The prime meridian and the 180th The value of a meridian is determined bymeridian divide the Earth into two equal the angle formed by drawing a line from thevertical parts—the Eastern Hemisphere to the Equator, at the point where the prime meridianright of the prime meridian and the Western crosses it, to the center of the Earth, and thenHemisphere to the left of the prime meridian. back out to another point on the Equator. See

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Figure 3-5.—Measuring meridians.

figure 3-5. The angle formed by theintersection of those two lines is the valueassigned to that meridian. In this way, theangles are measured around the Earth in bothan east and a west direction until you reach180°. Since there are 180° on each half of theglobe, you have a circle of 360°.

Each degree of longitude is subdividedinto minutes and seconds in the same manneras latitude. However, remember two thingsabout longitude:

1. West longitude is measured from rightto left on a map; east longitude is measuredfrom left to right.

2. When you write longitude in militarynotation, use seven numbers plus a letter toindicate east or west. When a position has lessthan 100° of longitude, a zero is added to theleft of the degree number; less than 10°, twozeros are added. For example: 0074321W for7 degrees, 43 minutes, 21 seconds west.

DIRECTION

We usually indicate direction from truenorth. We give directions in degrees, measuredclockwise from true north, or 000°T. We statecourses and bearings in three digits. In otherwords, 45 degrees is 045 (zero four five).Seldom is it necessary to consider compassdirection to a value smaller than a degree, eventhough each degree contains 60 minutes of 60seconds each.

A true bearing is the direction of an objectfrom the observer, measured clockwise fromtrue north. A relative bearing is the directionof an object measured clockwise from the ship’sbow. Objects seen by lookouts are reported interms of relative bearings by degrees. Seefigure 3-6.

The reciprocal a bearing is its opposite;that is, the point or degree on the opposite sideof the compass from the bearing. For example,the reciprocal of 180° is 000°. When you obtaina bearing on an object, the bearing from the

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Figure 3-6.—True and relative bearings.

object to you is the reciprocal of the bearingfrom you to it. To fmd the reciprocal of anybearing expressed in degrees less than 150°,simply add 180° to the bearing. If the bearingis 050°, its reciprocal is 050° plus 180° or 230°.If your bearing is greater than 180°, subtract180°.

In addition to true and relative directionmeasurement, there are other commonreferences, such as measurement from themagnetic pole and grid reference lines oncharts. However, all direction measurementsystems are based on the degrees in a circle orpoints on a compass rose.

The Cardinal Point System

For centuries, navigators used a system ofcompass readings, called compass points, toindicate direction. An observer would use thecardinal points of the compass (north, south,

Figure 3-7.—The mariner’s cardinal point system.

east, and west) and intervening points betweeneach cardinal point to indicate the direction ofan object. Figure 3-7 shows the 32 relativebearings by points around a ship. The cardinalpoint system may be used when a high degree

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Figure 3-8.—The mariner’s cardinal point system.

of accuracy is not required. Only the rules ofthe road and some harbor pilots and coastalmerchant mariners still express direction inpoints. Figure 3-8 shows a compass rose with16 points of the compass.

The Azimuth System

The azimuth system measures direction bydividing a circle into 360 equal parts, calleddegrees, and subdividing each degree intominutes and seconds. We measure direction indegrees, minutes, and seconds clockwise fromnorth in a horizontal plane. Some marinecompasses show both the cardinal point andthe azimuth figures on their cards. Figure 3-9shows a compass card with the azimuth systemand eight cardinal points superimposed on it.In this figure, the subdivisions of a degree arenot shown. For most navigational purposes,subdivisions of a degree are not necessary.

MAPS, CHARTS, ANDPROJECTIONS

To become knowledgeable in geographyand plotting, an understanding of maps, charts,and projections is extremely helpful. We willdiscuss these in the following paragraphs.

MAPS

A map is a graphic representation ofselected features of the Earth’s surface, drawnto scale. A map is a compact data base—aninformation storage and retrieval system—thatdoes not require machine action. Instead, theskilled map reader retrieves information fromthe map.

From another viewpoint, maps are two-dimensional models of the Earth. Topographicmaps are three-dimensional models that showelevation by using contour lines.

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Figure 3-9.—Compass card.

The graphic representations on maps mayconsist of

lines and symbols of various colors;

depths and locations of navigational aids. Anair navigation chart may show land, but itprovides the air navigator with elevations aswell as the locations of navigational aids.

drawings of landforms, called physio-graphic diagrams; or

photographs with the addition of linesand colors to emphasize features.

CHARTS

A chart is a special-purpose map, gener-ally designed for a form of navigation, such asair navigation. There is a difference betweencharts and maps. Maps show land areas,political subdivisions, and topography. Achart details water areas and has referencelines on it to allow the navigator tographically plot information. A hydrographicchart provides information such as water

PROJECTIONS

A projection is a method of representing athree-dimensional object on a two-dimensionalsurface. Cartographers (map makers) useprojection techniques to build maps or charts;however, it is impossible to project a three-dimensional object upon a two-dimensionalsurface without distortion. The type ofprojection they use depends on the area to berepresented and the use of the map or chart.

Distortion cannot be avoided, but it canbe controlled. Map makers have createdseveral projections to represent the Earth’ssurface on a plane. In any projection, theyestablish a network of lines corresponding togeographic coordinates. This network of lines

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Figure 3-10.—A Mercator projection.

enables them to place each detail. To use achart effectively, we must understand thepurpose of the projection system and its goodand bad features.

The Mercator projection, the mostcommon method of making nautical charts,was developed by a Flemish cartographer in thesixteenth century. The Mercator chart isprojected by fast placing a cylinder around theEarth, tangent at the Equator. Planes arepassed through the meridians and projected tothe cylinder upon which they appear as parallellines of longitude. Lines are drawn from thecenter of the Earth to the cylinder passingthrough the parallels to locate the lines oflatitude on the cylinder. Then, the cylinder iscut lengthwise and flattened. See figure 3-10.

Figure 3-11.—The difference between a great circleand a rhumb line on the Earth’s surface.

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Figure 3-12.—Mediterranean Sea.

The resulting horizontal and vertical linesform a simple Mercator projection. In theproduction of today’s Mercator charts,parallels are spaced by mathematical formulae.The advantage of a Mercator projection is thatit is a conformal chart, showing true angles andtrue distance. A rhumb line (a line that makesthe 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 aMercator chart is the distortion at highlatitudes. At the poles, meridians actuallyconverge; however, they are parallel on thechart. Greenland, in the higher latitudes on aMercator chart, appears larger than theUnited States, although it is much smaller.Even in the high latitudes though, thedistortion on a Mercator projection does notprevent the measurement of true distance.

AREAS OF INTEREST

We will conclude with a brief discussionof 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 Seahas been an influential factor in world affairsthroughout history. The Navy’s Sixth Fleetoperates from the Strait of Gibraltar at thewestern end of the Mediterranean, to the shoresof Israel, Lebanon, and Syria at the easternend. See figure 3-12. The Strait of Gibraltar isa vital choke point between the Mediterraneanand the Atlantic Ocean, as is the Suez Canal,which provides access from the Mediterraneanto the Red Sea and the Indian Ocean beyond.

MIDDLE EAST/PERSIAN GULF

The U.S. Navy has significantly increasedits role in this volatile area. The Commander,Joint Task Force Middle East, located atBahrain, is augmented by ships of both theAtlantic and Pacific Fleets. Atlantic Fleet shipsenter the Red Sea via the Suez Canal and thenproceed through the Gulf of Aden to the North

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Pag

e 3-

10.

Fig

ure

3-1

3.—

Mid

dle

Eas

t.

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Figure 3-14.—Western Pacific.

Arabian Sea/Gulf of Oman. To enter thePersian Gulf (also referred to as the ArabianGulf), ships must navigate another strategicchoke point, the Strait of Hormuz. See figure3-13.

WESTERN PACIFIC

The U.S. Seventh Fleet, headquarteredin Yokosuka, Japan, is responsible for this

large area. See figure 3-14. A carrierbattle group is homeported in Yokosuka toquickly respond to any regional tensions. Ournaval presence in the Southeast Asia area ischanged somewhat now with the loss of ourbase in Subic Bay, Republic of thePhilippines. Many of those support activitieshave relocated to Guam. Continued presencein the area is important to protect the Strait ofMalacca, the passage between the South China

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Sea, and the Indian Ocean. Pacific Fleetships enroute to the Arabian Sea/Persian Gulftransit this strait. It is also an importantcommercial route. Most of the tankers carry-ing Mideast oil pass through it on their way toPacific ports.

REFERENCE

Analysis and Reporting—Analysis Tools,NSGTP 683-14-44-90, Naval Educationand Training Program Management Sup-port Activity, Pensacola, Florida, 1990.

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A

Azimuth system, 3-6

C

Cardinal point system, 3-5 to 3-6Charts, 3-7Commercial time-conversion aids, 2-5Computations involving daylight saving time

(DST), 2-4 to 2-5Computations involving the International

Date Line, 2-4Computing time in geographic positions, 2-2

to 2-3Conversion from local time to ZULU time,

2-1Conversion from ZULU time to local time,

2-2

D

Daylight saving time (DST), computationsinvolving, 2-4 to 2-5

Designators "+" and "-", 1-2

E

Expression of time, 1-4

G

Geographic positions, computing time in, 2-2to 2-3

Geography and plotting, 3-1 to 3-12azimuth system, 3-6cardinal point system, 3-5 to 3-6

Geography and plotting—Continuedcharts, 3-7direction, 3-4 to 3-6geographic coordinates, 3-2latitude, 3-2 to 3-3longitude, 3-3 to 3-4maps, 3-6 to 3-7Mediterranean Sea, 3-9meridians, 3-1Middle East/Persian Gulf, 3-9 to 3-11parallels, 3-1projections, 3-7 to 3-9Western Pacific, 3-11 to 3-12

Greenwich mean time (GMT), 1-1 to 1-5expression of time, 1-4global division and designators, 1-1 to 1-2International Date Line, 1-4 to 1-5physical characteristics of time zones, 1-1

to 1-4zone-to-zone progression, 1-5

I

International Date Line, 1-4 to 1-5,2-4

L

Latitude, 3-2 to 3-3Literal (letter) designators, 1-2Local time to ZULU time, conversion from,

2-1Longitude, 3-3 to 3-4

M

Maps, 3-6 to 3-7Mediterranean Sea, 3-9

INDEX- 1

INDEX

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Mercator projection, 3-8 to 3-9Meridians, 3-1Middle East/Persian Gulf, 3-9 to 3-11

N

Numerical designators, 1-2

P

Parallels, 3-1Physical characteristics of time zones, 1-2 to

1-4

T

Time-conversion computation, 2-1 to 2-7commercial time-conversion aids, 2-5computations involving daylight saving

time (DST), 2-4 to 2-5computations involving the International

Date Line, 2-4computing time in geographic positions,

2-2 to 2-3

Time-conversion computation—Continuedconversion from local time to ZULU time,

2-1conversion from ZULU time to local time,

2-2time-conversion table, 2-5

Time theory, 1-1 to 1-6expression of time, 1-4global division and designators, 1-1 to 1-2Greenwich mean time (GMT), 1-1 to 1-5International Date Line, 1-4 to 1-5physical characteristics of time zones, 1-2

to 1-4zone-to-zone progression, 1-5

W

Western Pacific, 3-11 to 3-12

Z

Zone-to-zone progression, 1-5ZULU time to local time, conversion from,

2-2

INDEX-2

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Assignment Questions

Information: The text pages that you are to study areprovided at the beginning of the assignment questions.

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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 longitudetime zone theory and time computation. spans how many nautical miles?

1-1. What is another name for the 180thmeridian?

1. Equator2. Prime Meridian3. Greenwich Meridian4. International Date Line

1. 602. 1503. 6004. 900

1-6. What letter combination is correct in thestatement that follows?

1-2. Except for time zones MIKE andYANKEE, how many degrees oflongitude span each time zone?

Time zones in east longitude areA B

designated (plus) (minus) and must

1. 122. 153. 184. 25

C Dbe (added to) (subtracted from) local

time to obtain Greenwich mean time.

1-3. Time zone designations use 25 of the 26letters of the English alphabet. Whatletter is NOT used?

1. A; C2. A; D3. B; C4. B; D

1. A2. J3. Q4. X

1-7. A message originated at 191045S shouldbe assigned what ZULU DTG?

1-4. In time zone problems, the ZULU timezone (0) has a "+" designator.

1. 190445Z2. 190545Z3. 191545Z4. 191645Z

1. True2. False

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1-8. When you cross the International DateLine from the eastern hemisphere into thewestern hemisphere, you always subtracta day.

1. True2. False

1-9. It is always the same time, but never thesame day, in time zones NOVEMBERand YANKEE.

1. True2. False

1-10. At the equator, what is the approximatewidth, in nautical miles, of a time zone?

1. 5002. 9003. 15004. 1800

1-11. When the local time in Tokyo, Japan, is210600I, what is the local DTG inPensacola, Florida (time zone SIERRA)?

1. 2015002. 2016003. 2120004. 212100

1-12. Washington, D.C. (39N 077W) is in whatlettered time zone?

1. QUEBEC2. SIERRA3. ROMEO4. UNFORM

1-13. What is the local DTG in zone PAPA at1700A?

1. 13002. 14003. 20004. 2100

1-14. What is the local DTG in zone DELTAwhen it is 032200Q?

1. 0406002. 0422003. 0306004. 031400

1-15. The ZULU time zone passes throughwhich of the following countries?

1. Finland2. England3. Australia4. Commonwealth of Independent States

(former Soviet Union)

1-16. What letter combination is correct in thestatement that follows?

The continental United States

(CONUS) spans four time zones

which are designated zonesA B

(E through H) (R through U)C

and are numbered (+5 through +8)D

(-5 through -8).

1. A; C2. A; D3. B; C4. B; D

1-17. If it is 1500U on 30 September, what isthe local DTG in time zone MIKE?

1. 291900 SEP2. 301100 SEP3. 011000 OCT4. 011100 OCT

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1-18. It is 100500 local time in zone +2. Whatwill be the local DTG, 10 hours later, inzone -4?

1. 0923002. 1010003. 1011004. 102100

1-19. A ship at 3840N 11221E is in what timezone?

1. +72. +83. -74. -8

1-20. When the time in Manila is 120600H,what is the local DTG in Denver (timezone TANGO)?

1. 1115002. 1315003. 1221004. 112100

1-2 1. What is the local DTG at 14400E when itis 0430 local time on 1 October at17500W?

1. 3006302. 0102303. 0201304. 020230

1-22. If it is 0300 local time on 31 May aboarda ship in the North Atlantic (2200W),what is the local DTG in Moscow (-3time zone)?

1-23. It is 0500Z on 7 March. What is the localDTG in Honolulu (2720N 15642W)?

1. 0715002. 0714003. 0619004. 061800

1-24. A message transmitted at 051000I fromTokyo is received in Washington, D.C.,(3800N 07730W) one hour later. What isthe local DC DTG at the time of receipt?

1. 052300H2. 060000H3. 042000R4. 042100R

1-25. Your ship is at 0105N 05000E. Anunidentified submarine has been locatedat 0045N 06930E. Approximately howmany nautical miles is your ship from thesubmarine?

1. 5852. 9753. 11704. 1950

1-26. A ship is at 0027N 04230W at 102300Z.What is the local DTG aboard the ship?

1. 102000C2. 102000P3. 110200C4. 110200P

1. 302300 MAY2. 310700 MAY3. 310800 MAY4. 310700 JUN

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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 radiomanaboard the USS WHITE PLAINSintercepted the garbled position report infigure 1A from a vessel in distress.Assuming the transmission time (0415)reflects the local time at the vessel’sposition, what is the probable longitude?

1. 01830E2. 02830E3. 01830W4. 02830W

1-28. A message originated in Moscow (-3time zone) at 200625Z was received by aship in the +12 time zone at 211325Y.How long was the message en route?

1. 1 hour and 25 minutes2. 28 hours3. 31 hours4. 43 hours

1-29. An airplane departs Kennedy Airport(N.Y.) at 1130 local time on 14 June forPakistan (time zone ECHO). If the flighttime is 14 hours and 17 minutes, what isthe local DTG when it arrives inPakistan?

1. 1420472. 1417473. 1511474. 151447

YOU ARE ABOARD A COAST GUARDC U T T E R O N P A T R O L I N T H EPACIFIC. YOUR RADIOMAN HASJUST RECEIVED THE PARTIALPOSITION REPORT IN FIGURE 1BFROM AN UNIDENTIFIED VESSEL.THE TIME OF RECEIPT IS 220706ZA N D T H E P O S I T I O N O F Y O U RCUTTER IS 0005N 17130W. USE THISINFORMATION AND FIGURE 1B TOANSWER QUESTIONS 1-30 THROUGH1-32.

1-30. What was the local DTG aboard yourship at the time the position report wasreceived?

1. 2114062. 2120063. 2214064. 222006

1-31. Assuming the time of the position report(1705) reflects the local time at theunidentified vessel’s location, what is thecorrect longitude?

1. 15505W2. 15505E3. 17505W4. 17505E

1-32. The unidentified vessel is in what timezone?

1. KILO2. LIMA3. XRAY4. WHISKEY

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1-33. You depart San Francisco by ship at0857 local time on 28 June for Japan.The time en route is 11 days, 12 hoursand 37 minutes. What is the local DTGin Japan (time zone INDIA) when youarrive?

1. 092134 JUL2. 100634 JUL3. 101434 JUL4. 111434 JUL

1-34. A ship at 3500N 04520W is in what timezone?

1. +32. +43. -34. -4

1-35. A missile launched at 0800Z on 1 Mayimpacts 35 minutes later at 3950N17630E. What is the local DTG in thetarget area at impact?

1. 301935 APR2. 302035 APR3. 011935 MAY4. 012035 MAY

THE PRESIDENT OF THE UNITED STATESHAS JUST SENT AN URGENT COMMUNI-QUE FROM THE WHITE HOUSE TO THEAMBASSADOR TO BRAZIL IN RIO DEJANEIRO. THE DTG OF THE MESSAGE IS212205Z. RIO DE JANEIRO IS SOUTH OF THEEQUATOR IN TIME ZONE PAPA.

FIGURE 1C

IN ANSWERING QUESTIONS 1-36 AND1-37, USE THE INFORMATION INFIGURE 1C.

1-36.

1-37.

1-38.

1-39.

What was the ZULU DTG in Rio deJaneiro when the communique wasoriginated?

1. 2201052. 2202053. 2119054. 212205

What was the local DTG in Washington,D.C., when the message was originated?

1. 2117052. 2120053. 2203054. 220705

You are onboard the USS CON-STELLATION which is transiting thePacific east to west. Your currentposition is 0027N 17820W. You receivea report of an unidentified aircraft at0030N 15540E. Approximately howmany nautical miles separate the carrierfrom the unidentified aircraft?

1. 4002. 7203. 15604. 1880

When time is given in daylight savingtime, you add one hour to arrive at thezone’s "normal" time.

1. True2. False

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1-40. Your parents are on vacation in Sydney,Australia, (time zone KILO) and havetold you they will call you at 0630 on 1June (Australia time). You are in SanAngelo, Texas, (time zone SIERRA)and the CONUS is currently on daylightsaving time. At what local San AngeloDTG will your parents call?

1. 311430 MAY2. 311530 MAY3. 010230 JUN4. 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 checkon your next set of orders. At what localDTG should you place your call tocontact your detailer on 30 June at 1500local Washington, D.C. time?

1. 301000 JN2. 302200 JN3. 010100 JL4. 011100 JL

1-42. At 1100Z, a French ship using zoneCHARLIE time sends a message to yourship stating that their commandingofficer will be visiting your ship at 1500.How much time does your ship have toprepare for the VIP visit?

1. 1 hour2. 2 hours3. 3 hours4. 4 hours

1-43. Assume you are planning a TAD trip toTokyo, Japan (time zone INDIA). Youare 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 yourpoint of contact to meet you at Tokyo’sInternational Airport?

1. 300100 APR2. 291100 APR3. 010100 MAY4. 011100 MAY

1-44. If a missile was fired at 1316 local time on4 February from a location in time zoneINDIA and the impact area had alongitude of 17700E, what would be thelocal DTG in the impact area when themissile hits if the flight time is 16minutes?

1. 041032Y2. 041032M3. 041632M4. 041632Y

AS YOUR BATTLE GROUP PATROLS IN THEPACIFIC AT 0015N 17015W AT 2245Z ON 30APRIL, YOUR PICKET DESTROYERLOCATES AN ENEMY AIRCRAFT CARRIERAT 0026N 17145E.

FIGURE 1D

IN ANSWERING QUESTIONS 1-45THROUGH 1-47, REFER TO FIGURE1D.

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1-45.

1-46.

1-47.

1-48.

1-49.

At the time the position of the enemycarrier was obtained, what was theapproximate distance between it andyour battle group?

1. 620 NMs2. 1080 NMs3. 1440 NMs4. 1880 NMs

What was the local DTG at the positionof the enemy carrier at 302245Z?

1. 300945 APR2. 301245 APR3. 010845 MAY4. 010945 MAY

What was the local DTG at the positionof your battle group at 302245Z?

1. 301145 APR2. 301245 APR3. 011045 MAY4. 010945 MAY

A Russian ship departs Vladivostock(time zone -9) at 101327 local time andarrives in Vancouver, B.C., (time zone+8) exactly twelve days later. What wasthe arrival time of the vessel?

1. 210600H2. 212027U3. 230600H4. 232027U

At 0915Z on 22 December, the USSLONG BEACH, located at 4130N16845W, launched a surface-to-surfacemissile. Forty-live minutes later, ahelicopter observed the splash-down ofthe missile at 4045N 17015E. What wasthe local DTG in the impact zone at thetime of splash-down?

1. 212100X2. 222000L3. 222100L4. 230700M

Learning Objective: Identify geographicreference and direction systems.

1-50.

1-51.

1-52.

1-53.

1-54.

Which of the following is a characteristicof the prime meridian?

1. It passes through the RoyalObservatory at Greenwich, England

2. It runs true north and south3. It divides the Eastern and Western

Hemispheres4. Each of the above

Which of the following imaginary linesis a parallel that divides the Earth inhalf into Northern and SouthernHemispheres?

1. The Prime Meridian2. The Great Circle3. The Equator4. The 180th Meridian

The latitude of a given point locates thatpoint relative to its distance from theequator.

1. True2. False

In geographic coordinates, each degree isdivided into which of the followingsubunits?

1. 30 minutes2. 30 seconds3. 60 minutes4. 60 seconds

Which of the following designationsrepresents a point that is two-thirds ofthe way from 35° north to 36° northlatitude?

1. 352000N2. 352020N3. 354000N4. 354020N

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1-55. A person traveled from Greenwich,England, until reaching a meridiandesignated 90°. In which of the followingdirections could the person havetraveled?

1. East only2. West only3. East or west4. North

1-56. A relative bearing is the direction of anobject measured clockwise from which ofthe following reference points?

1. The ship’s bow2. Magnetic north3. The object4. True north

1-57. What is the reciprocal of 280°?

1. 0902. 1003. 1804. 200

1-58. A ship steaming at an azimuth of 315° isheaded in which of the followingdirections?

1. Northwest2. Southeast3. Northeast4. Southwest

Learning Objective: Recognize characteristicsof maps and charts.

1-59. Which of the following phrases defines achart?

1. A chart details land areas only2. A chart is a map that is used only by

navigators of ships3. A chart is the background upon which

a map, showing a portion of theearth’s surface, is superimposed

4. A chart details water areas and is usedprimarily for navigation

8

1-60. Map makers use which of the followingmethods to represent three-dimensionalobjects on a two-dimensional surface?

1. Hydrographics2. Geographic coordinates3. Topography4. A projection

1-61. In the construction of a Mercator chart,the surface of the Earth is projected uponwhich of the following shapes?

1. A plane tangent to the Earth2. A sphere tangent to the equator3. A cylinder tangent to the equator4. A cone tangent to the pole

1-62. Which of the following phrases describesthe appearance of meridians on aMercator projection?

1. Vertical lines that are parallel andequally spaced

2. Parallel lines whose spacing increasesas longitude increases

3. Straight lines that intersect at the poles4. Curved lines that bend toward the

point of tangency

1-63. Which of the following is a disadvantageof a Mercator chart?

1. Distortion near the equator2. Distortion at high latitudes3. True distance cannot be measured4. Parallel spacing is distorted

Learning Objective: Identify geographic areasthat hold interest to the Navy.

1-64. What is the choke point that a ship mustnavigate to pass from the Atlantic Oceanto the Mediterranean Sea?

1. Suez Canal2. Strait of Hormuz3. Strait of Malacca4. Strait of Gibraltar

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1-65.

1-66.

1-67.

1-68.

1-69.

What U.S. Navy fleet operates in theMediterranean Sea?

1. Second2. Third3. Sixth4. Seventh

The island of Crete in the MediterraneanSea is located nearest to which of thefollowing coordinates?

1. 3125N 03015E2. 3900N 00430E3. 3500N 02500E4. 3430N 03500E

A ship entering the Red Sea via the SuezCanal will steer what approximateheading to reach the Gulf of Aden?

1. SSE2. ENE3. S4. SW

The eastern side of Saudi Arabia isbordered by what body of water?

1. Arabian Sea2. Red Sea3. Gulf of Oman4. Persian Gulf

Ships entering the Persian Gulf from theGulf of Oman must navigate whatstrategic choke point?

1. Suez Canal2. Strait of Hormuz3. Strait of Malacca4. 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 isclosest to your location?

1. Oman2. Saudi Arabia3. Egypt4. Iraq

What strategically important body ofwater lies between Japan and Korea?

1. Pacific Ocean2. Yellow Sea3. Sea of Japan4. South China Sea

What U.S. Navy fleet is responsible foroperations in the Western Pacific area?

1. Second2. Third3. Sixth4. Seventh

A ship departing Guam on a heading of350° is most likely destined for which ofthe following countries?

1. Philippines2. Indonesia3. Japan4. Taiwan

The Strait of Malacca is an importantpassage between which of the followingtwo bodies of water?

1. Pacific Ocean and Sea of Japan2. Pacific Ocean and South China Sea3. South China Sea and Indian Ocean4. Indian Ocean and Coral Sea

Your ship is near 1800N 11200E on aheading of 015°. Which of the followingports of call will you soon be visiting?

1. Manila, Philippines2. Hong Kong3. Tokyo, Japan4. Jakarta, Indonesia

9

DAPS DAPS
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