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The Traveler: The Past, Present, and Future of Navigations
University of Southern California
Lucine Agazaryan
lagazary@usc.edu
(818) 569-9844
December 10, 2012
Lucine Agazaryan is an undergraduate student at University of Southern California majoring in
Computer Science and Business Administration. Her passion for traveling encouraged her to
research the past, present, and future of navigations.
Abstract:
Our ancestors had to go through extreme measures to keep from getting lost. They read the stars
in the night sky and used compasses to steer ships towards their destinations. The Global
Positioning System, or GPS, created by the Department of Defense, has become a part of our
daily lives by providing step-by-step directions to our destinations. This article is devoted to
demystifying the GPS system and GPS receivers. After a broad overview of the history behind the
modern marvel, how the satellites and receivers work, and the limitations of the receivers, the
article works its way back down to Earth, discussing the receiver’s uses. The importance of
future applications and the future of a new GPS system are also studied.
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Introduction:
The distance around the Earth is 24,906 miles, containing seven continents and 196 official
independent countries. These countries are kept alive by a vast maze of roads and highways that
connect people and allow for modern travel. In the 21st century,
individuals wonder how they would ever live without the
Global Positioning System, also known as the GPS. Can you
remember life before Mapquest, Google Maps, and GPS? When
people had to read the stars in the night sky, draft detailed maps,
and map out routes long before leaving their homes? Today, for
around $80, one can purchase a GPS receiver that will tell them
exactly where they are located on Earth at any given moment
(Figure 1). This article investigates the GPS navigation system:
the history of the system, the creation of the device, the way the
receiver works, the potential problems, the usages, and the
future applications of GPS.
Figure 1: Garmin - nüvi 30 Automobile
Portable GPS Navigator for $80.91 at BestBuy
http://www.bestbuy.com/site/Garmin++n%FCvi+30+Automobile+Portable+GPS+Navigator/415
1133.p?id=1218456939096&skuId=4151133
History:
In the early 1500s as international commerce and travel spread, finding ways to map one’s
position became much more urgent. In 1675, the Royal Observatory was established by Great
Britain in Greenwich “…for the very purpose of measuring star positions in order to help the
sailors of the British Royal Navy and the Merchant Navy navigate safely across the sea” [1]. In
the 1700s, the captains of the sea struggled to measure latitude (x-coordinate) and longitude (ycoordinate), which can now be automatically measured in GPS receivers. While measuring
latitude (highest point in the Sun's daily motion across the sky) was comparatively easy,
measuring longitude was much more difficult since navigators needed to know the accurate time.
The way they set their clocks was by observing eclipses of the moons of Jupiter [2]. Currently,
GPS receivers use atomic clocks – which provide the most accurate time standards – to receive
time information [3]. If digital maps could sing the old song “Anything you could do I could do
better” to their paper counterparts, they would be right. Nowadays, a GPS receiver can show
latitude, longitude, time, and much more with relative ease and unparalleled mobility.
How Was the GPS Developed?
American scientists figured out that if they knew a satellite’s precise orbital position, they could
accurately locate their exact position on Earth “by listening to the pinging sounds and measuring
the satellite’s radio signal” [4]. The first NAVSTAR (Navigation Satellite Timing and Ranging),
the official name for the U.S. GPS Program, satellite was launched by the U.S. Department of
Defense (DoD) in 1974 to test the concept (Figure 2) [4]. After the test, the Global Positioning
System was restricted for government use until the immediate aftermath of a disaster. In 1983,
269 passengers died on Korean Air Lines Flight 007 upon being shot down after entering Soviet
airspace because of a navigation error [5]. Due to this tragedy, President Ronald Reagan ordered
the United States military to make the Global Positioning System available for civilian use.
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Figure 2: A NAVSTAR GPS satellite
undergoing pre-launch testing.
http://en.wikipedia.org/wiki/GPS_%28satellite%29
How does it Work?
A Global Positioning System (GPS) consists of 27 Earth-orbiting satellites (NAVSTARS), 24 in
operation and three extra in case one fails [6]. Each of these 3,000 to 4,000 pound solar-powered
satellites orbits about 12,000 miles above the Earth (Figure 3) [4]. Airplanes usually fly no
higher than six miles, and the space shuttle orbits at 230 miles, which gives an idea of just how
high up the satellites are [7]. Each GPS satellite orbits the earth once every 12 hours, making two
complete rotations every day [6].
The satellites are positioned in such a way that a GPS receiver can
receive signals from at least six of the satellites at any time and
location on Earth [4]. To calculate a 2D position (latitude and
longitude) and track movement, a GPS receiver must be locked on to
the signal of at least three satellites [6]. To calculate a 3D position
(latitude, longitude, and altitude), a GPS receiver needs four or more
satellites in view [6]. In general, the more GPS satellites your
receiver can get a fix on, the more accurate the information will be.
Once the user's position has been determined, the GPS unit can
calculate additional information, including speed, trip distance, and
time.
A GPS receiver goes through a process of steps to determine its location. First, the almanac data
tells the GPS receiver where each GPS satellite should be at any given time throughout the day
[4]. The data is constantly transmitted and stored in the GPS receiver’s memory. The difference
in time between when the satellite sent the signal and when the receiver received it is compared.
The GPS receiver and the satellite create identical pseudo-random code. The pseudo-random
code is simply an I.D. code that identifies which satellite is transmitting information (this number
can be viewed on your GPS receiver’s unit's satellite page) [4]. When the GPS receiver receives
the code, it uses the Doppler shift principle (determines how much code needs to be shifted) for
the codes to be matched. The shift is multiplied by the speed of light (186,282 miles per second)
to determine the distance between the satellite and the receiver [4]. Using this information, from
several satellites, the receiver pinpoints the exact location of the user. This information is
converted to the coordinate system of the user’s choice and the user’s current location is ready
for use.
GPS satellites work in any weather conditions, anywhere in the world, 24 hours a day. In
addition to buying a receiver to access and make use of the data, there are no subscription fees or
setup charges to use the GPS. Each satellite is built to last approximately 10 years theoretically,
but their actual lifespan varies [7]. A satellite’s lifetime is not governed as much by the reliability
of the electronics, as by other factors such as battery life and fuel capacity.
Limitations of the Receiver:
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According to the government and GPS receiver
manufacturers, a GPS receiver is accurate to within
49 feet (15 meters) in general [8]. However, a number
of factors can reduce the accuracy of a GPS receiver.
For example, atmospheric conditions such as
variations in atmospheric plasma, temperature,
pressure, and humidity can result in satellite signals
being significantly slowed [4]. Another problematic
factor is multipath errors: when the GPS signal is
reflected off a hard surface (such as buildings) before
it reaches the receiver, a delay in time occurs (Figure
4) [3]. Frequently, timing errors are due to the
receiver’s less precise clock [4]. Evidently, the clock
inside the receiver is not as accurate as the four atomic clocks onboard each satellite. Another
factor that can potentially interfere with the GPS signal is the number of satellites visible to the
GPS receiver. The GPS receiver has difficulty receiving satellite data if a significant part of the
sky is blocked with dense foliage, buildings, canyons, and mountainous area [4]. Many have
experienced this problem while attempting to make the receiver work indoors or in parking
garages.
In addition to technological limitations, GPS users have to be aware of problems arising from
their own negligent behavior. A major issue society overlooks is blind faith in technology. For
instance, the Anchorage Daily News reported on August 24, 2012 that an unnamed man drove
his car into the water while taking directions from his GPS [9]. He relied on the receiver to
navigate him to the ferry in the town of Whittier, but he had driven a little more than 100 meters
when the receiver told him to make a right, and he blindly followed the directions despite the
evidence of his eyes [9]. People must remember that technology can sometimes be faulty and use
common sense when utilizing a GPS receiver.
Are GPS users losing a skill?
The human mind is surprisingly good at developing “mental maps” of an area. By relying on a
GPS receiver, are users losing this skill? Physical maps help us build cognitive maps. By
remembering the positions of landmarks and the relations between locations passed along a
route, users “develop survey knowledge (stored in the mind like a mental map),” allowing users
to locate destinations and find shortcuts [10]. A negative side effect of relying on GPS receivers
is that users are not building up their cognitive maps, which causes the hippocampus, the region
of the brain responsible for cognitive maps, to exhibit inactivity
[10]. According to one neurologist, “…our brains act
economically: they try to decrease the amount of information to be
stored (by relating new thoughts to already known content) and
avoid storing unnecessary information” [10]. However, in an
increasingly busy world, the GPS, with its remarkable power and
ability, can help people avoid unnecessary stress.
GPS Usages:
In addition to being used as a mapping tool for travelers, GPS can
also be used for locating restaurants, gas stations, movie theaters,
airports, lodging, hospitals, and banks. On hand-held devices that
include Google Play Store or Apple Store, users have access to free
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or paid applications that allow users to make connections and interact with the world. One
particularly useful app, “Trapster,” is an application that allows drivers to report red-light
cameras, speed cameras, or cops hiding near speed traps (Figure 5). There are also locationbased games that give users an interactive way to explore their surroundings, giving audio tours
and turning cities into real-world games [11]. Whether a user is commuting to work or on a road
trip, they may want to take a quick nap without the fear of missing a bus or train stop. There are
apps that can track a user’s location and trigger an alarm at the inputted destination [12]. If a user
does not want to travel by bus or train and prefers to catch a cab, there are apps designed to give
a list of local cab companies so users can call a company to catch a nearby cab [12]. When a user
desires some company while at a store or a coffee shop, a “check-in” allows other users to know
where the user is located. A new generation of online dating has emerged using GPS based
dating apps. This is how Sam Hyde met his fiancée, Nina [13]. When he checked in, he saw
Nina’s check-in was at the same location and messaged her asking to meet up. Sam and Nina
told a reporter from South Mississippi, “we just locked eyes and it was love at first site; love at
first text” [13].
The Future of GPS:
Modern technology rapidly evolves and so does the GPS. GPS units have already been integrated
into wrist watches and PC Cards, but GPS receivers will continue to get smaller. Not only will
they become easier to view with the improved brighter screens, but they will also become easier
to use. GPS is continually becoming to an integral part of our everyday lives. In the future GPS
will become a staple in all electronic devices as people become more dependent on them. On
September 15, 2012, Mashable Tech reported that a simple click of the heels could navigate you
back home [14]. Created by British designer Dominic Wilcox, the “No Place Like Home GPS
Shoes” are programmed to guide a user to their destination anywhere in the world (Figure 6)
[14]. Wilcox was inspired by The Wizard of Oz’s protagonist, Dorothy Gale, who got lost
because of a tornado and wanted to return home. To activate the GPS, the user uploads their
destination through a custom-made mapping software and a USB cable [14]. With a series of
LED lights installed in the toe box, the user is guided by step-by-step directions toward their
desired destination.
Figure 6: “No Place Like Home GPS
Shoes” created by Dominic Wilcox
http://mashable.com/2012/09/15/gps-shoes/
Many users take GPS for granted in the same way they do with the Internet and assume it is free
to generate locations at any time and place. Hence, users tend to neglect the fact that GPS is
owned, operated, and controlled by the United States military, which can cut or control access at
any time. The solution to this problem is Galileo, a GPS system currently under construction
with the intention primarily for civilian use. Galileo is estimated to be 6-7% of European GDP,
or €800 billion by value [15]. The GPS will be Europe’s own system consisting of 30 satellites
(27 operational and 3 active spares) [15]. The estimated date of completion is 2018 but they are
continuously making progress: the first two Galileo In-Orbit Validation satellites were launched
on October 21, 2011 by Soyuz ST-B (Figure 7) and two more are scheduled for launch this year
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[15]. GPS is a modern marvel that has allowed numerous generations to easily travel to and from
their destinations. After analyzing the history, the way the satellites and the GPS receivers work,
and the usages of the device, we can expect future applications and developments to overcome
the limitations of the device and provide all users with future application to improve quality of
life.
ADD VIDEO ON WEBSITE: http://www.esa.int/esaNA/galileo.html
GIOVE-A
GIOVE-B
Figure 7: Two experimental Galileo satellites, GIOVE-A and
GIOVE-B are part of the first step in the orbit validation of the
Galileo system.
http://www.esa.int/esaNA/SEM5KHXEM4E_galileo_0.html
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References:
[1] P. Murdin, Full Meridian of Glory: Perilous Adventures in the Competition to Measure the
Earth. New York: Copernicus Books, 2008, pp. 4.
[2] O. Zuravicky, Map Math: Learning About Latitude and Longitude Using Coordinate
Systems. New York: The Rosen Publishing Group, 2005, pp. 12.
[3] A. El-Rabbany, Introduction to GPS: The Global Positioning System. Norwood: Artech
House Inc., 2002, pp. 31-33.
[4] J. McNamara, GPS For Dummies. Hoboken: Wiley Publishing, 2008, pp. 50-56.
[5] T. Mahnken, Technology and the American Way of War. New York: Columbia University
Press, 2008, pp. 160.
[6] Garmin. “What is GPS?” Internet: http://www8.garmin.com/aboutGPS/. [December 10,
2012]
[7] R. Broida, How to Do Everything with Your GPS. Emeryville: McGraw-Hill, 2004, pp. 2-4.
[8] S. Featherstone, Outdoor Guide to Using Your GPS. Chanhassen: Creative Publishing, 2004,
pp. 68.
[9] MCT News Service, (2012, Aug. 24). “Alaskan man drives car into harbor while following
GPS directions.” Channel 6 News. Internet:
http://www.channel6newsonline.com/2012/08/alaskan-man-drives-car-into-harbor-whilefollowing-gps-directions/ [December 10, 2012].
[10] J. Frankenstein. (2012, Feb. 5). “Is GPS All in Our Heads?" The New York Times.
Internet:http://www.nytimes.com/2012/02/05/opinion/sunday/is-gps-all-in-ourhead.html?_r=3. [December 10, 2012].
[11] Apple. “iTunes Store Top 10 Apps” Internet:
http://www.apple.com/euro/itunes/charts/apps/top10appstoregames.html. [December 10,
2012].
[12] E. Biba. (2009, Jan. 19). “Inside the GPS Revolution: 10 Applications That Make the Most
of Location.” Wired. Internet: http://www.wired.com/gadgets/wireless/magazine/1702/lp_10coolapps?currentPage=all [December 10, 2012].
[13] C. Holmstrom. (2012, Sep. 18). “Finding Love with GPS.” WLOX 13. Internet:
http://www.wlox.com/story/19518012/finding-love-with-gps [December 10, 2012].
[14] A. Li. (2012, Sep. 15). “GPS Shoes Guide You Home With a Click of the Heels.” Mashable
Tech. Internet: http://mashable.com/2012/09/15/gps-shoes/ [December 10, 2012].
[15] European Space Agency. (2012, Sep. 14). “About Galileo.” ESA-Navigation. Internet:
http://www.esa.int/esaNA/galileo.html [December 10, 2012].