GPS Systems

by Caribou Betty

What is a GPS ?


Technology by and large excels. Every place in this whole wide world that you look at, even the places that you cannot see with your naked eye, speak of the advancement of existing technology. The GPS (Global Positioning System) is one of those amazing technologies.

It enables you to keep track of your journey, locate destinations, and hunt places you have never been to previously. Gone are the days when people had to ask others to guide them to their specific destinations; now we have GPS in different forms meant for delivering the highest level of customer convenience.

You can have your GPS with you 24/7. Whether you are driving, fishing, walking, playing, hiking, or hunting, you can use it for assistance. Every new technology is assumed to be a breakthrough, but a GPS is more so! This device is extremely beneficial and has multiple applications to get the best use possible.

A GPS is a highly versatile device capable of working across all weather types and locations, such as on land, underwater, in the air, and so forth. It works through signals via satellites. The signals transmitted through the satellites are specific to the GPS device, which guide the user towards a particular location.

Prior to the use of GPS units installed in motor vehicles, people got from place to place by using maps, checking the location of the sun, or asking someone working at a gas station. This lead to many misadventures, since the sun is not visible 24 hours a day, and while the directional information gleaned from gas station attendants may have been helpful and well meaning, it wasn’t always accurate. Hence, a map and a compass on the dashboard was the technology of the old days.  However, today, the widespread use and applications of the Global Positioning System (GPS) has revolutionized how we get from one place to another.

Technology Behind GPS system?

Global Positioning System Satellies

Global Positioning System Satellites

The Global Positioning System is a two-part navigation system. The first part is in space and is composed of 31 satellites orbiting 12,600 miles above the Earth’s surface. Each satellite is sending a constant stream of signals to GPS receivers located on or near the Earth’s surface. The GPS satellites in space are called a constellation. GPS satellites move at a speed of about 7,000 miles per hour, making two complete trips around the Earth each day. Of the 31 GPS satellites in space, 24 of them are up and operational at all times, and the other seven are used as back-ups. The back-ups are used if one of the satellites has a malfunction, which is referred to as “unhealthy”. Since each satellite has its own specific orbital path, you can sit, stand, walk or fly, almost anywhere on, or near Earth and be in the line sight of at least six GPS satellites, at any time of the day.

The second part is GPS devices on Earth that receive information from the satellites that are in its clear line of sight and determines, mathematically, your precise location on Earth. It displays that information to you on a GPS unit display screen in an easy to understand format. Not only can your GPS unit tell where you are, but it can also give you other vital information such as:

  • The distance from you to the green on the 14th hole
  • How far you have walked or, and at what speed
  • Where the Thai restaurants are in your area
  • Find the perfect fishing spot
  • Locate your campsite when you get lost, no need to leave a trail of breadcrumbs

Click to Read about History of Global Positioning System

How Does GPS Work?

The three major components to the Global Positioning System are Space, Control and Users.

Space is the constellation of GPS satellites that orbit 12.600 miles above the Earth’s surface. Each satellite is about 17 feet wide when its solar panels are extended. A satellite makes its twice-daily trip around the Earth using solar power. It is equipped with a battery for back-up power (when the Earth blocks out the solar rays). It has rocket boosters that can be used to make slight corrections if it happens to veer off its designated orbital path. It also has an atomic clock on board, which is the most accurate, and most expensive timepiece used by humankind.

However, unlike the name implies, it is not radioactive.

The final part of the GPS satellite is the radio transmitter, which uses less than 50 watts to send a constant stream of radio signals to Earth. Information that is sent to the receivers on Earth at the speed of light (radio signals) is:

  • the I.D. code of the satellite
  • if the satellite is working
  • where the satellite should be in its orbital path
  • date and time the signal was sent, down to the nanosecond level

Control of the GPS system is carried out by the United States Air Force. Air Force personnel work at the Master Control Station in Colorado 24 hours a day, 7 days a week. Six monitor stations located around the world constantly receive information from the GPS satellites, and then forward that information to the MCS (Master Control Station). If a correction needs to made, Air Force control personnel first mark the satellite as “unhealthy” and take it off-duty. They temporarily replace the unhealthy satellite with a spare “healthy” one. Then MCS control personnel make the correction and forward the correction to a dedicated GPS antenna, which transmits the correct data to the appropriate satellite. Control also synchronizes all the atomic clocks on the satellites within a few nanoseconds of each other.

Users are the tens of millions of civilians like you and me who own and operate a GPS device that receives GPS satellite signals, along with the United States military. A typical GPS device has an antenna and a receiver that tunes in to the low-frequency satellite signals. It generally has more than 20 different channels for capturing those signals, a receiver-processor, and an excellent clock. The clock is not as excellent, or as accurate as an atomic clock, but it does not need to be because the atomic clocks on the satellites are constantly “telling” our GPS receivers what time it is. Besides, all our GPS units would cost about $100,000 each if they came with their own atomic clock. Finally, a typical GPS device has an excellent display screen showing a map as to where we are, the speed we traveling, estimated time of destination arrival, etc.

How exactly does a Global Positioning System work for Me?

You are lost, and you ask your GPS unit to tell you where on Earth am I? Your GPS device chooses four satellites in its line of sight at four different locations in the sky. Your GPS unit then receives information from each of the four satellites:

  • its pseudorandom, or I.D. code identifying itself
  • its status (healthy or unhealthy)
  • the current time and date
  • where that particular satellite should be at that time of day, according to its almanac

Your GPS then calculates the distance between you and each of the four satellites by determining how much time it took to receive a signal from each satellite. The speed of a radio signal is a constant 186,000 miles per second. Therefore, the length of time to receive the signal is in direct relation to the distance between you and the four satellites. Then it uses trilateration, where, picture this, it views each of those four satellites as the center of its own sphere, and where all four of those spheres intersect, is where you are at, baby! Your GPS unit will then display the correct latitude, longitude and altitude within feet of your own two feet.

Is the Global Positioning System Accurate?

GPS is extremely accurate, but there are some factors that may affect its accuracy:

  • the atmosphere
  • radio signals bouncing off objects before reaching the receiver
  • the position of the satellites in the sky
  • an error in the receiver clock
  • the government intentionally downgrading the signals

However, it is possible to reduce some of those errors in accuracy.

  • Differential GPS: So far, we have assumed that the radio signals coming from the GPS satellites travel at a constant rate (the speed of light). But our atmosphere can actually slow down that signal very slightly, causing an error in calculation of our location.

The ionosphere and troposphere seem to slow radio signals down the most, and DGPS, or Differential GPS provides data to reduce the error in the GPS calculation by employing a system of land-based beacons to transmit the corrective data to GPS receivers. Additional hardware or software for your GPS device is usually required for DGPS.

  • WAAS: The Wide Area Augmentation System basically does the same thing as the DGPS. The difference between the two is that some GPS units are equipped with WAAS capability, so there is no need to purchase extra hardware or software. The Wide Area Augmentation System operates with 25 ground reference stations in the continental United States, a master station on each coast and two geostationary satellites positioned near the equator.

The ground reference stations receive signals from the GPS satellites, adjust the calculations for atmosphere or satellite path error, then forward the correct data to the geostationary satellites, and they forward the correct information to your GPS. WAAS is considered to be five times more accurate than an ordinary GPS unit is, and twice as accurate as DGPS.

  • GPS Reception can be affected if your GPS device is near tall buildings, mountains or densely forested areas. Your GPS will receive the signal, but the amount of time that it bounces off tall solid objects will affect the calculation of where you are in relation to the satellites.
  • Clock Error: The clock in your receiver is of high quality, and it is constantly being synchronized with the atomic clocks attached to the satellites. However, occasional location mistakes will happen if your receiver clock is wrong by just a fraction of a second.
  • Selective Availability: The United States government owns the GPS satellites and the systems that operate it. They allow civilians to use GPS as a national resource free of charge. The U.S. government can take away civilian use of the GPS in time of war.

How does GPS make our lives easier ?

The uses or applications of GPS devices are virtually unlimited. This relatively new technology has already found myriad applications in a wide range of organizations. Some of them are:

Marine GPS will not only show you where you are and how to get to your destination, but will help you find the best place to fish on coastal waters, inland lakes and rivers. Some have sonar attachments to assist in shallow waters, or to determine how deep you want to drop your fishing line. Other features of a waterproof marine GPS may include track plotting and chart plotting.

Sports GPS assists runners, bicyclists and even swimmers. The waterproof GPS designs are either small, lightweight handheld devices, or a wristwatch design packed with features like speed, distance, average times, best speeds and distance to go.

Hiking and Hunting GPS are known for their rugged durability. The handheld units are popular with people who love to hike mountain bike, fish, hunt, camp and even do some geocaching. They feature easy to read screens even in bright sunlight, and a long lasting battery.

Automotive GPS uses are so numerous I don’t know where to begin. They can be used in personal cars, fleet vehicles, trucks, motorcycles and RV’s. They may be used for navigation as well as tracking a vehicle’s speed or route. Some parents have GPS trackers installed on their teen driver’s cars to monitor their driving habits and behavior.

Golf GPS have become very popular. Some are pre-loaded with the layout of over 20,000 golf courses. Golfers can purchase them in the small, durable handheld or wristwatch design. The GPS will not only tell you the distance between you and hole, but also locate and alert you to hazards such as sand traps and water. Some can even record average distance from each club you used, or display easy to read layup charts.

GPS has boosted efficiency and productivity in many sectors of our economy. Some of the commercial applications for the Global Positioning System include:

  • Communications
  • Banking and finance
  • Power grid coordination
  • Package delivery
  • Construction
  • Mining
  • Aviation

GPS has also been extremely useful in the public sector. It is a national resource that we paid for as taxpayers, and continues to pay us benefits by saving lives that probably would have been lost without it:

  • Emergency services
  • Search and rescue
  • Disaster relief
  • Environmental protection

How to Choose a GPS

With so many brands, price ranges and types of GPS devices on the market, choosing one that is right for you can become a difficult task. Here are some suggestions to help you find your GPS.

Choose Your Application. What will be the function of your GPS? Do you need a GPS for your vehicle because you travel a great deal? Are you an avid hunter and need to know where public and private land begins and ends in a particular area? Choose the application that is right for your needs.

Price Range. Live within your means. With so many different brands and models, you should be able to find a GPS that has the features and applications within your budget.

Different Brands are Good for Different Applications. It is comparable to purchasing a car. Certain car brands are known for fuel economy, some for reliability, and others for luxury. The same things apply to GPS. Find a brand that excels in the application you are searching for.

Ease of Use. A GPS that is user-friendly and intuitive is much better than the model that has a manual as thick as a dictionary.

Durability and Rugged Casing. Things happen to our electronic devices. They are dropped on the floor, get wet, or sit out in the sun. Those events should not be end of your GPS. Find one that is tough.

Readability for Day and Night. Struggling to read a GPS display screen while driving is not good. Nor is it good to be standing in the middle of a desert at noon and not be able to read your GPS display screen because the sun is too bright. It is vital to read the display screen when there is no light, a little light, or too much light.

Interface and Connectivity. Do you need to transmit data from your Marine GPS to someone on land? Or are you a pilot that needs to receive data from someone on the ground? How is the connections done, and is there any additional software costs?

Signals and Reception. Receiving signals is very important. Some GPS receivers are very temperamental and fade in or out with the slightest interference. Signal reliability and the number of channels to receive a signal are key factors.


Options are numerous and so are the applications of Global Positioning Systems. Technology has always been a step forward, just like this one. Above are the features and benefits of a number of GPS types while there are several others too. One can keep on exploring the device to get the best use possible under given circumstances.

Using a GPS instead of a map is both convenient and safe. Get rid of understanding the map while driving because not only is it difficult to be a multitasker but such multitasking carries huge risk too. Every commercial and recreational activity is useless if it forcibly pushes you in a dangerous situation.

So whether you are driving a vehicle or a boat; or you are playing, hiking, hunting, or simply walking; stay safe using a Global Positioning System and say “When the going gets rough, let’s get going!”



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