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VOICE ONE:
This is Steve Ember.
VOICE TWO:
And this is Phoebe Zimmermann with the VOA Special Englishprogram, EXPLORATIONS. Today we tell about a device you can hold inyour hand. It permits you to find your way across mountains, throughdeserts and across oceans without ever getting lost.
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VOICE ONE:
Let us begin back on Junetwenty-seventh, Eighteen-Fifty-One. We are on the sailing ship,”Flying Cloud,” in the Atlantic Ocean. The Flying Cloud is under thecommand of Captain Josiah Cressy.
For many days now, Captain Cressy has made the huge ship travelat speeds that were not thought possible. The crew is frightened bythe speed. No ship in history has ever traveled this fast. The crewalso is frightened because the ship is sailing in some of the mostdangerous waters in the world.
The Flying Cloud is near Cape Horn at the end of the SouthAmerican continent. The weather has been bad for several days. Theperson responsible for guiding the ship must be able to see the Sunor a star to know the position of the ship. The stormy weather hasprevented this for several days.
VOICE TWO:
The person who plans thedirections for a sailing trip is usually the ship’s captain. On theFlying Cloud, however, the captain’s wife does this job.
Her name is Eleanor Cressy. She is famous as an expert navigator.She has planned this trip through the dangerous waters near CapeHorn. Many underwater rocks are found here. To guide the shipsafely, she must know where the ship is at all times.
Eleanor Cressy must use a method called “Dead Reckoning” becauseshe has not been able to see the Sun or stars to find the ship’strue position. Dead Reckoning is extremely difficult. It is partscience, and part estimate.
To find the position of the Flying Cloud, Missus Cressy must usethe last known position of the ship. She also has to consider theship’s direction, its speed and the movement of waves or the oceancurrent.
Here, near Cape Horn, she is permitted no mistakes. Many shipshave sunk in this part of the world. Hour after hour, Eleanor Cressyuses mathematics to find the ship’s Dead Reckoning position. Shedoes this again and again, carefully searching for mistakes. Thelives of the crew and the future of the ship are her responsibility.
VOICE ONE:
Eleanor Cressy demonstrates her great skill at navigation thenext day. On the morning of June twenty-ninth, Captain Cressy cansee Cape Horn, just eight kilometers to the north. The ship isexactly where Eleanor said it should be. It is safe and willcontinue on to San Francisco, California, faster than any sailingship ever.
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VOICE TWO:
Eleanor Cressy’s job in Eighteen-Fifty-One was important andextremely difficult. The job of navigator did not change much untilthe middle of the Twentieth Century. At sea or on land, finding thecorrect direction to travel has always been a problem.
However, within the past several years, the problem of navigationhas greatly changed. Dead Reckoning navigation is a thing of theancient past. Now, people do not need the skills of Eleanor Cressyto navigate. They can use a simple device that will permit them tonavigate anywhere in the world. It uses a technology called “GlobalPositioning System,” or G-P-S.
VOICE ONE:
G-P-S is able to show your exactposition on Earth. Weather does not affect the device. Many G-P-Sdevices can be held in the hand. Some are larger, and meant to beplaced in ships, automobiles, trucks, airplanes or other aircraft.
Whatever the size, the device works much the same way. The G-P-Sdevice is a radio receiver. It receives information from twenty-foursatellites in orbit around the Earth. The satellites are placed sothat a G-P-S device on the surface of the Earth can receiveinformation from at least four of the satellites at any time.
VOICE TWO:
A satellite sends information, including the exact time at whichit is operating. It also sends information about the position ofother satellites.
This information travels from the satellite to the G-P-S deviceat almost the speed of light. But the satellite is far enough awayto permit the device to measure the distance.
The G-P-S device uses the time the information was sent to findits distance from the satellite. The device measures the exactdistance to four satellites to establish its position on Earth. TheG-P-S device can do this second by second, minute by minute, dayafter day and arrive an the correct answer all the time.
You can place the device in a ship, a car or other movingvehicle. Then you can watch the position information change as thevehicle moves. In fact, the G-P-S device will give both yourdirection and the speed you are traveling.
VOICE ONE:
The United States government owns the twenty-four satellites thatprovide the information for G-P-S. The Department of Defensecontrols the satellites.
The first G-P-S satellite system was called NAVSTAR. It waslaunched in February, Nineteen-Seventy-Eight. The NAVSTAR satelliteswere created to provide extremely correct navigation information toAmerican military ships and aircraft.
A few years later, President Ronald Reagan signed a document thatpermitted information from NAVSTAR to be used by anyone. He did thisafter a Korean Air Lines flight was lost. The Korean airplane hadflown by mistake into airspace over the Soviet Union innineteen-eighty-three. It was shot down by Soviet military aircraft.President Reagan said the American satellite navigation system wouldhelp prevent such accidents in the future.
It costs nothing to use the satellite information. All you needis a G-P-S device to receive the information.
The least costly G-P-S devices sell for about one-hundreddollars. The smallest devices can be held in the hand. Devices foraircraft or ships are larger. They may cost several thousands ofdollars.
VOICE TWO:
After President Reagan permitted the public use of Americannavigation information, several electronics companies began makingthe G-P-S devices. However, there was a problem. The DefenseDepartment would not let the satellites send the exact informationto the public. Defense officials made sure the satellites sentinformation with mistakes. This was done so the information couldnot be used by military forces of any future enemy.
In May of two-thousand, the United States announced that such asecurity measure was no longer needed. The government turned off theequipment preventing satellites from providing the correctinformation.
Today, a G-P-S device that receives information from foursatellites at the same time will show your correct position on Earthto within ten meters. It can also tell you the speed of yourvehicle, the direction you are traveling, how far you have traveled,and the distance remaining until the end of your trip.
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VOICE ONE:
G-P-S devices are popular in the United States. Many companiesmake and sell them. Most of the devices come with a receiver thatlooks like a small television. The less costly G-P-S devices provideinformation in black and white. More costly ones provide theinformation in color.
Many G-P-S devices can be linked to computers. The computersplace information into the device including maps of city streets andmajor roads between cities.
The user of the device enters information using the controls. TheG-P-S provides information about the direction of travel and tellshow to get where you want to go. The device will correctly guide youfrom road to road and street to street, warning before a left andright turn must be made. The device also remembers where it hasbeen. So it can guide the G-P-S user home again.
Recently, some companies started producing G-P-S devices thatspeak the directions. A person driving a vehicle does not have tolook at the device for information. A person only has to listen.Here is an example. This G-P-S device is from the Garmin Company.Listen as the voice gives directions.
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VOICE TWO:
As you can see, the new G-P-S devices can help anyone get towhere they want to go. And, they can do this just as well as thefamous Eleanor Cressy did one-hundred-fifty years ago.
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VOICE ONE:
This VOA Special English program was written by Paul Thompson andproduced by Caty Weaver. This is Steve Ember.
VOICE TWO:
And this is Phoebe Zimmermann. Join us again next week foranother EXPLORATIONS program on the Voice of America.
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