首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Longitude and Latitude The meridians of longitude are imaginary great circles drawn from pole to pole around the earth. By
Longitude and Latitude The meridians of longitude are imaginary great circles drawn from pole to pole around the earth. By
admin
2013-09-28
93
问题
Longitude and Latitude
The meridians of longitude are imaginary great circles drawn from pole to pole around the earth. By international agreement, the meridian of longitude passing through Greenwich, England, is numbered zero. The earth is divided into 360 degrees, and the meridians are numbered east and west from Greenwich. There are 180 degrees of longitude east of Greenwich and 180 degrees in the westerly direction. New York has a longitude of 74 degrees west (74oW.) which means that it lies on the 74th meridian west of Greenwich.
Since the sun appears to travel around the earth in 24 hours, it will move 360/24 or 15 degrees in one hour. This reasoning can be used by navigators to determine their longitude. Imagine that we have set sail from Greenwich, England, after having set a very accurate clock, or chronometer, to the local Greenwich time. As we travel westward toward New York, we notice that the sun is going "slower" than our chronometer. At the time that our timepiece reads 12 o’clock, the sun has not quite reached the zenith. As a matter of fact, when our clock reads noon, what it really means is that it’s noon in Greenwich, England. Our clock continues to tell us the time, not at our present location, but at Greenwich. Let us wait until the sun is directly overhead (noon at our location) and then read the time on our clock. Suppose it reads i o’clock. This means that there is one hours difference in time between our longitude and that of Greenwich. As we mentioned earlier, this corresponds to exactly 15 degrees of longitude, so our longitude must be 150 W. The world is divided into 24 time zones, and each zone corresponds to 15 degrees of longitude. New York is approximately 5 time zones west of Greenwich, so the time difference must be about 5 hours. By maintaining chronometers on Greenwich time, ships can determine their longitude on any sunny day by merely noting the difference in hours between Greenwich time and local sun time and multiplying this difference by 15 degrees.
Of course, longitude gives only half of the information needed to determine our precise location. We must also know our latitude, which tells us how far we are north or south of the Equator. The Equator is the zero line for the measurement of latitude. Circles are drawn parallel to the Equator to indicate other values of latitude. There are 90 degrees of south latitude.
In the Northern Hemisphere there is a star called Polaris almost directly over the North Pole. This makes it possible to determine the latitude of a given point by setting our sextant (六分仪) to measure the angle between Polaris;the North Star, and the horizon. Mathematicians tell us that this angle is equal to the latitude at the point in question.
To get idea of our location, therefore, we need to know local time, Greenwich time, and the angle between Polaris and the horizon.
In order to establish the "fix" or precise location of a ship, the navigator must know________.
选项
A、his latitude
B、his longitude
C、local time
D、both his latitude and longitude
答案
D
解析
转载请注明原文地址:https://kaotiyun.com/show/F8LK777K
0
专业英语四级
相关试题推荐
Whatarethetwospeakerstalkingabout?
Letchildrenlearntojudgetheirownwork.Achildlearningtotalkdoesnotlearnbybeingcorrectedallthetime.Ifcorrecte
TheDragonBoatFestival(端午节)isoneoftheimportantnationalfestivalsinChina.WriteonANSWERSHEETTHREEacompositionofa
Comparedwith2009,whichofthefollowingfiguresremainedaboutthesamein2010?
Starsarepublicpeoplewhoarepermanentlyinthespotlight.Somecomplainthattherearenowhereforthemtohide.Newspapers,
WriteonANSWERSHEETTHREEanoteofabout50-60wordsbasedonthefollowingsituation:You’velearnedthatyourfriendJimm
TheDiscoveryofAstronomersThediscoveryofplanetsarounddistantstarshasbecomelikespace-shuttlelaunches—newsworthy
ItisobviouslynecessarythatboththePresidentandhisadvisers______downtoearth.
Thattrumpetplayerwascertainlyloud.ButIwasn’tbotheredbyhisloudness_______byhislackoftalent.
Katya’s______loveofjusticecausedhertochampionanyonesheconsideredtobetreatedunfairlybysociety.
随机试题
关于血液功能的叙述,错误的是
A.肝B.心C.脾D.肺E.肾
流量,是指单位时间内通过特定表面的流体(液体或气体)的量(体积或质量)。当流体量以体积表示时称为体积流量;当流体量以质量表示时称为质量流量。根据上述定义,下列选项含有对体积流量描述的是()。
春之怀古张晓风①春天必然曾经是这样的:从绿意内敛的山头,一把雪再也撑不住了,噗嗤的一声,将冷面笑成花面,一首澌澌然的歌便从云端唱到山麓,从山麓唱到低低的荒村,唱入篱落,唱入一只小鸭
“视其所以,观其所由,察其所安”所体现德育原则是()
白居易在《大林寺桃花》一诗中描述道:“人间四月芳菲尽,山寺桃花始盛开。”这两句诗所蕴含的哲学寓意是()。
2014年,全国粮食播种面积112738.3千公顷,比2013年增加782.7千公顷。其中谷物播种面积94622.8千公顷(141934.1万亩),比2013年增加854.1千公顷,增长0.9%。全国粮食总产量60709.9万吨,比2013年增长0.9%
如果消费者消费的X、Y商品的价格之比是2,它们的边际效用之比是5,为达到效用最大化,消费者应当()。(河南财经政法大学,2011)
Dr.WhiteandMr.Lihavenotmetbefore.
Wheredoesthewomanwanttogo?
最新回复
(
0
)