There are a lot of options when it comes to GPS and GNSS hardware so it can be hard to just pick one and start logging locations. The size, update rate, power requirements, these are all features that you'll want to look into before you choose which hardware is right for your project.
This is something you need to consider if your project is supposed to be pocket-sized. GPS and GNSS modules are getting ever-smaller (Your tiny, tiny cell has one in it!) but remember that in general, the antenna has to shrink to fit the module which will affect things like lock time and accuracy.
The update rate of a GPS or GNSS module is basically how often it recalculates and reports its position. The standard for most devices is 1Hz (Only once per second). The fact is, unless you're on an airplane or something, you're probably not going fast enough to have changed position significantly in the past second. However, UAVs and other flying or fast vehicles may require faster update rates to stay on track. 5 and even 10Hz update rates are becoming more and more available for cheap. Keep in mind, though, that a fast update rate means that there's more NMEA sentences flying out of the module, some microprocessors will be quickly overwhelmed trying to parse that much data. On the plus side, if you have a module that runs at 5 or 10Hz, it can usually be configured to run at an easier pace.
If someone asked you to crunch a bunch of numbers that you had to get from satellites in orbit around the Earth and use that information to figure out where you were, you'd flat out refuse. It's a lot of work, and yet that's exactly what these tiny GPS/GNSS units are doing (multiple times per second!) so they can use a lot of power. On average, around 30mA at 3.3V. Keep in mind, also, that GPS antennas usually enlist the help of an amplifier that draws extra power. If a unit appears to have super-groovy-low power consumption, make sure there's an antenna attached.
Even though there are only so many GPS/GNSS satellites in view at any given time, the number of channels that your module runs will affect your time to first fix. Since the module doesn't know which satellites are in view, the more frequencies that you can check at once, the faster you'll find a fix. After you get a lock, some modules will shut down the extra blocks of channels to save power. If you don't mind waiting a little longer for a lock, 12 or 14 channels will work just fine for tracking.
Many modules come with this chunk of something on top of it. What is that? That is a precisely made chunk of ceramic. Each antenna is finely trimmed to pickup the GPS L1 frequency of 1. GHz. Sound expensive? Well, they make a lot of them. There are some other GPS antenna technologies (chip, helical), but they are not as common, a bit more expensive, and require significantly more amplification and filtering.
Oh hey - as I mentioned, the satellites are in the sky like... 12,552 miles above you, so be sure and point the ceramic towards the sky, ok? GPS and GNSS antennas are getting better, and you can certainly get a signal indoors, but it's hit-or-miss. I hear there are reception problems in the urban canyons of places like New York City. If you can get near a window - it will help a lot.
How accurate is GPS and GNSS? Well it varies a bit, but you can usually find out where you are, anywhere in the world, within 30 seconds, down to +/- 10m. Amazing! I say +/- because it can vary between modules, time of day, clarity of reception, etc. Most modules can get it down to +/-3m, but if you need sub meter or centimeter accuracy, it gets really expensive. I've heard stories of such fabled receivers, but I have never gotten to touch one. Someone please prove us wrong.
So you&#;re wondering what the difference is between GPS and GNSS? Good news, you&#;re not alone and you&#;ve come to the right place! The topic of GPS vs GNSS can be confusing for many people. The main reason for this is that in the US, we tend to use a specific GNSS called GPS. You can learn more in our article explaining each of the world's geospatial satellite constellations!
It is difficult enough looking for the right GNSS antenna or module. There are many options to choose from, and getting the most popular GNSS option may not be the best choice for your application. [Read our article on "GPS vs GNSS"] Yet as the number of GNSS systems increases and navigation technology improves, keeping track of GNSS choices can be challenging.
Augustine Nguyen, Applications Engineer at Symmetry Electronics, provides a few considerations for those adding GNSS to their design.
It may be easy to account for GPS, but how about BeiDou or Galileo? Different regions use different GNSS systems, and if your product has a regional focus, it&#;s best to know the corresponding GNSS system to build around.
&#;This is an important factor to consider when designing a product because adding support for multiple GNSS systems requires additional testing during the production process,&#; says Augustine Nguyen. &#;Each GNSS system serves a specific set of regions with their own regulations, and certification is required before the product can be introduced to a region. This can be a lengthy and expensive process &#; which any project manager would need to consider.&#;
GNSS systems available or planned to be available in the future are GPS (USA), Galileo (European Union), BeiDou (China), GLONASS (Russia), NAVIC (India), and QZSS (Japan).
The answer depends on the global reach of the application. Is the product a domestic product, with a strong focus on a specific region, or will the product extend across other parts of the world?
&#;Do you want your product to provide GNSS capabilities for multiple regions around the world? You are essentially dictating the demographic you are selling to. It comes down to how flexible and versatile you want your product to be. For example, your cell should have location tracking no matter where you are in the world, therefore supporting multiple GNSS systems. An application focusing primarily on domestic farmers, on the other hand, would only need to support the GNSS system that pertains to that specific region. Supporting only the regions you need keeps the product cheaper and easier to produce.&#;
Take into consideration the dimensions of the product, as well as the size of the PCB. Augustine explains further:
&#;Knowing the size of the product is important because the dimension of the product and its PCB determines where you can place the antenna. Poor placement of the antenna would affect the antenna&#;s performance. The size of the antenna also changes how the antenna behaves. The antenna&#;s output power, efficiency, and directivity are the major parameters that can be affected by poor design.&#;
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Internal, or external? Soldered or connected via cable? Location determines the optimal performance of the system and the user experience.
"The location of the antenna on your product&#;s PCB affects the radiation pattern and efficiency of it. Depending on the type of antenna, the size of the PCB&#;s ground plane should always be considered in comparison to the antenna manufacturer&#;s reference plane and calculated values. The manufacturer&#;s data sheet of that particular antenna only gives you the general idea of how it performs and will often bear no resemblance to the antenna performance on your final product. This is because antenna manufacturer use reference boards (that are of a specific size) to ONLY provide a baseline of their product&#;s performance.
The location of the antenna also has to do with how you want your design to look like. You don&#;t find GNSS antennas external to the enclosure of the because it would be unattractive. There is a balancing act between the product&#;s functionality and its aesthetics.&#;
Not all antennas are the same, and good manufacturers go above and beyond to make sure buyers are satisfied. Choose reputable parts for quality and service. A specialty distributor can help you find the right antenna and avoid costly mistakes along the design cycle.
Finding the right solution for your specific needs is key to successful design. The size of the product, location of the antenna, and geographic range are important factors to consider before adding GNSS to your design.
Ethertronics offers antennas of all sizes to accommodate your product needs.
For smaller antennas mounted on the surface of a PCB, Ethertronics offers internal antennas that are placed inside the enclosure of the product as a surface-mounted device, or SMD.
Ethertronics: (SMD) - Prestta Standard GPS Embedded Ceramic Chip Antenna
Ethertronics: M (SMD) - GPS Savvi Ceramic Chip Antenna
Ethertronics: (SMD) - Embedded GPS ISM Stamped metal SMT Antenna
Ethertronics EtherHelix
Ethertronics also offers bigger, external or off-board antennas connected to the PCB via a coaxial cable with RF connectors at both ends (SMA, u.FL). These external antennas are either placed outside the enclosure of the product or off the products PCB to provide more design flexibility.
Ethertronics: - EtherHelix Mission Critical GPS Antenna
Ethertronics: - GPS Active Patch Antenna
In addition to industry-leading wireless antennas, Ethertronics has an in-house team of engineers to help analyze your product or system and fine-tune your RF design around your application for optimal performance. Click here to see the selection of Ethertronics antennas available.