There are many methods that can help your device send coordinates. Each has upsides and downsides: cost, power needs, accuracy, etc.
Let's look at the 3 most common ones, from the least accurate to the most accurate:
1) Atlas positioning
Atlas positioning is based on a proprietary probabilistic calculation of the most probable location of the device. This is done thanks to the Received Signal Strength Indicator (RSSI) coming from the messages sent by a device and received by the Sigfox infrastructure. It doesn't rely on TDOA (Time Difference Of Arrival) or on the signal Doppler shift.
The location computation is based on the data obtained from the Sigfox infrastructure. This data comes from several replicas of the same messages sent by a device and received by different base stations.
With the identifiers of the base stations, the Sigfox infrastructure can assert their location. Thanks to this information, probable locations are computed, the one with the highest probability being selected.
Because this method is calculated using regular Sigfox messages, it has two main advantages:
- No extra hardware required,
- Very cost-efficient,
- Message payload can be empty, or used for regular data handling.
Moreover, it benefits from advantages of the Sigfox network:
- Low energy for a longer battery life,
- Very long range and global (up to 50 territories covered or in progress) with the capacity to automatically switch from a radio configuration (RC) to another thanks to the Monarch feature,
- Resilient to interference, with the capacity to resist jamming.
It does have limitations:
- The computation method (using RSSI and base station location) allows to have an accuracy in kilometers (1 to 10 km precision (0.6 to 6 mi)) for more than 80% of the messages, depending on the environment and the base station density in the considered territory. Moreover, the access to the service strongly depends on the Sigfox network coverage in the dedicated territory.
Sigfox-based location is perfect for solutions which are high-volume, don't need much precision, and where battery life is key. Here is a guide on how to create a geolocation callback on our backend platform.
2) Wi-Fi positioning
One common method to find the position of a device is to listen to Wi-Fi networks around it. To position itself, the device matches these networks to a Wi-Fi hotspot database through Sigfox.
Using Wi-Fi positioning allows the customer to benefit from a good accuracy (thanks to the maximum range of Wi-Fi access points: 200 meters) without setting-up an ad hoc infrastructure (such as RTLS solutions), on a global scale.
How does it work?
- The device (equipped with Wi-Fi hardware) "listens" to the different networks around it and recognizes the two strongest ones.
- The device sends the Media Access Control address (or MAC@) of those Wi-Fi networks through the Sigfox network. A Wi-Fi network's MAC@ is 6 bytes, so two MAC@s are perfect for a Sigfox message (12 bytes).
- Once received on your platform, the MAC@s are sent to a Wi-Fi hotspot database for matching.
- The hotspot database server answers with an approximate position (25 to 50 meters, 82 to 158 ft).
This method has many advantages:
- Works both in indoor and outdoor, with high density in urban areas,
- Energy consumption is average,
- Accuracy: 25 to 50 meters (82 to 158 ft).
It also some has its disadvantages:
- Wi-Fi hardware is required,
- Only works if Wi-Fi networks are available,
- Wi-Fi infrastructure is, by nature, evolving,
- Access to the Wi-Fi hotspots database is rarely free.
You can see a quick implementation example here on GitHub.
3) GPS positioning
The most common way of obtaining geolocation is through the GPS method. By adding a GPS module to your hardware, you will know the position of your assets very easily.
How does it work?
- The GPS module listens to the satellites in sight.
- Once done, the coordinates are sent through the Sigfox network. A GPS coordinate is usually stored on 6 bytes, so you can send 2 GPS positions within a single Sigfox message.
- The data is then transmitted to your own server and can then be located on a map.
GPS has multiple advantages:
- Highly precise (up to 15 meters / 49 feet),
- Widely used,
- Works almost everywhere on the planet.
It has also its disadvantages:
- High battery consumption,
- Not very efficient indoor,
- Expensive hardware.
You can find an example tutorial of Sigfox + GPS here.
What is the best method for my project?
Because it involves modules, the most fitting method depends on the use-case you're targeting. While the Sigfox Atlas is better for use-cases needing high battery life, some will prefer the GPS method for its high precision, or even Wi-Fi for indoor use. It all depends on what your device needs to achieve.
A good solution is sometimes a mix of some of them, and that is why module manufacturers are making available hardware that includes the three technologies on board.
Atlas Suite is a Sigfox service that provides the geographic coordinates of a device within a confidence radius of accuracy.
Atlas Suite comprises two services: Atlas Network and Atlas Wi-Fi.
The service is based solely on Atlas positioning, without GPS or any additional component. The geographic coordinates are computed from diverse information coming from the Sigfox infrastructure and messages. Atlas Network is available for all Sigfox devices in all areas where the network is deployed, without any GPS or other location technology.
The combination of two technologies, Wi-Fi and Atlas positioning, for a high indoor and outdoor accuracy. The geographic coordinates are computed from both the Wi-Fi and Sigfox infrastructure information, which allows a higher accuracy in urban and industrial areas. The combination of these two location technologies ensures a high availability of the location information and its continuity in all types of geographic environments (indoor and outdoor).
|Atlas||Everywhere||1 to 10 km|
|Atlas + Wi-Fi||Indoor
|50 to 200 meters|
|Atlas Network||1 to 10 km||$||Excellent||Excellent||Good|
|Atlas Wi-Fi||50 to 200 meters||$$||Good||Excellent||Excellent|