Thanks to the efforts of brilliant engineers and scientists, GPS (Global Positioning System) is a cornerstone technology in our world today. Whether it's from our vehicle's navigation system or a handheld device while hiking through the woods, we are now able to pinpoint our exact latitude and longitude from satellites orbiting the earth. Pretty crazy, right? Come along with us and learn what it is, how it works and how you can make your own GPS system.
Learn about the history of GPS, how it works and how it came to be an integral technology in today's world.
At Medium Earth Orbit (12,550 miles), there are approximately 31 satellites in operation at any given time. This is a relatively large system, run with careful planning and calibration. The principle idea is math. Wait! Let me finish. Your receiver pinpoints location by calculating the distance between you and that satellite. This is done by multiplying the rate of signal (speed of light) by the atomic clock time on the satellite. You can get your location from three satellites, but it will not be as accurate – four satellites are needed to determine your location in three dimensions. Three satellites are needed for x, y and z coordinates, and one satellite to determine the time it took the signal to travel from the satellites to the receiver (see images below).
Ok, cool. So satellites are zipping around spitting out location data, and if I’m in the line of sight then my receiver will tell me my location. Is that it? No, not exactly. We’ve just taken a small step into GPS technology as a whole. We’ve established there are two key parts, satellites and receivers, so now let’s look closer. A receiver is usually a chip that can receive an electromagnetic wave and translate it into readable data. These systems can range from a standalone chip, to a breakout board, to a fancy complete user system, like in a car. If you’re making a project around these types of technologies, you’ll have to understand the three main features they all need to work. For a GPS module you’ll need an antenna, an integrated system to perform math and data communication, and a communication protocol output that feeds to the user or end system.
Any wireless communication system will feature the almighty antenna. In short, we’re looking for a conductive metal that, when hit with electromagnetic waves, an electric current inside the conductor will flow. Think of slapping a pool and watching waves ripple on the water. This current flows in a specific way, controlled by the electromagnetic wave. There is an entire engineering discipline dedicated to making antennas, so we won’t go too deep. But, this is an important component for the next part of the system.
There is no exact standard for this portion, but we need electronics to filter out unwanted wave frequencies and read the ones we’re interested in. These systems can be complex, as with GPS-RTK, or simple for regular GPS. A basic recipe would be a filter, signal decoder and some communication output. We use a variety of chips, and each has their own advantages and disadvantages. So how do we communicate with these chips?
Let's assume you’ve heard of or have some experience with common communication methods between electronics, like Serial, I2C, SPI, etc. These are hardware-level, computer-to-computer communication methods, but GPS has an extra layer on top. How do we account for many satellites zipping around spitting out their own languages? We introduce GPS communication protocols, which is just a fancy way of saying standardizing. Meet the NMEA-0183 standard: this basically breaks down signals into sentences.
When the signal is decoded into this standard, the once-electromagnetic wave becomes readable to humans. Throw it on communication method lines, and our computer can show us our location.
If you would like to learn even more about GPS, check out our GPS Basics page below.
Now that we've covered the basics with GPS, it's time to dive right in. We've put together a simple, effective tutorial to introduce you to the hardware and coding needed to build your first global positioning system.
With technological advances in GPS receivers, we are able to achieve positional accuracy to one centimeter. This is possible through what is called real-time kinematics (RTK). RTK-capable GPS receivers used to be thousands of dollars and were limited to professional surveyors and government groups, but now they can be used by anyone, for a fraction of the cost.
As with any technology, GPS hardware comes in many shapes and sizes to fit the specific needs of your project. Below we have listed a few of our favorite breakout boards, antennas and modules.
Take a look at our GPS Buying Guide for a full list of products, specs, and information to help you build the system right for you.
GPS breakout boards are equipped with a receiver, and have the ability to interface with your favorite development boards, such as a SparkFun RedBoard Qwiic.
Some projects require an antenna to better recieve signals from the satellites. Below are some of our favorites.
GPS modules are the signal receivers. These modules come without a breakout board, so interfacing with these modules may increase difficulty of a project.
Here are a few other projects that use GPS. We are always trying to expand our library of projects and tutorials, so check back often or fill out the form above to be notified of new content.