Locating your assets is an essential part of your business. There are a dozen practices ranging from maximizing asset usage, scheduling maintenance to tracking different assets like containers, trailers, pallets, etc. Geolocation is helping businesses worldwide to get the most optimal value out of their asset fleet.
This blog post explains and compares four different geolocation technologies: GPS, Bluetooth, WiFi, and network-based geolocation. We will compare their advantages and disadvantages and show that combining different geolocation technologies within your supply chain logistics can drastically improve operational efficiency. But first things first… What is geolocation exactly?
Geolocation refers to any type of technology that is capable of identifying the geographic location of a device. By locating an asset tracking device in real time, you can locate an important asset, such as a container, a trailer, a pallet, etc.
Often the tracking device is a mobile phone or an internet-connected device (Internet of Things). Let’s dive a little deeper into four different types of geolocation technologies and their pros and cons.
Zooming in on GPS, BLE, WiFi and network-based geolocation
Global Positioning System, was originally developed for military navigation but nowadays anyone with a GPS device can receive radio signals that these satellites broadcast. This global satellite system provides geolocation and time information to a GPS receiver almost anywhere on the Earth if there are no obstacles and at least three GPS satellites available.
A big plus of GPS is its accuracy. It can locate something up to five meters precisely or even better with dual-band GPS receivers. The accuracy depends on many factors and it is also important to take into account the time it takes to determine a position, the fix time.
Best results are obtained when the GPS antenna has clear sky view. Contrary when the GPS signal is reflected or obstructed it can take much longer or even become impossible to get an accurate position. The longer it takes to get a GPS fix, the more energy is consumed.
There is also an important distinction between a cold fix and a hot fix. A cold fix is determining a position when no satellite data is available, for example after a period of inactivity. When the tracking device already has acquired satellite positions because it is constantly tracking it can find much faster an accurate position, this is a hot fix.
A battery-powered tracking device that has to work for multiple years will not frequently determine positions, it has to do cold fixes. Your smartphone that needs recharging after one day on the other hand can do hot fixes as it has the luxury to do GPS fixes frequently.
Another advantage is that GPS works everywhere outdoors and there is no specific infrastructure required. The downside is that this geolocation technology requires quite some energy because it has to listen to several satellites and this can take some time especially in the case of a cold fix. Other disadvantages are that long distance communication can be interrupted by weather-related situations and its inability to work indoors.
Where GPS can therefore be used as an outdoor positioning technology, WiFi and Bluetooth can be used side by side for positioning indoors.
GPS in short
- Accurate outdoor positioning (up to five meters)
- Works almost everywhere outdoors
- No additional infrastructure required
- High energy use
- Does not work indoor
- Risk of interruption by weather-related situations
Bluetooth Low Energy
Bluetooth is a wireless short-range communications technology standard. It’s mainly designed for communicating over short distances. The signals do not carry very far, even in optimal circumstances devices need to be within 100 meters. Although Bluetooth has been around for two decades, its latest version, Bluetooth Low Energy (BLE) is making big strides in geolocation and positioning.
- Geobeacon (Fixed-location BLE beacon): a BLE location marker on a fixed location advertises its position over BLE. The tracking device receives this data and reports the position to the end-user
- BLE gateway: the tracking device announces its presence via BLE to a BLE gateway on a fixed location. The BLE gateway identifies the tracking device and reports its position to the end-user
Fixed-location BLE beacons (Geobeacons)
Geobeacons act as a location marker. These are devices emitting a BLE signal which tracking devices use to identify their location. So when you install geobeacons on known locations, the beacon will broadcast their identifier. The tracking device nearby identifies the broadcaster, the geobeacon, and uses this to determine its position.
Advantageous to geobeacons is the fact that there is no interaction required with existing IT infrastructure for communication. The beacon itself is the minimal infrastructure that has to be installed.
This geolocation technology works accurately outdoors and indoors. The more geobeacons you install , the more accurate the positioning of your asset will be.
The main argument to use BLE technology is the fact that the battery lifetime is guaranteed for many years. This technology consumes very low power and can easily be installed into your existing logistics infrastructure.
A battery-powered beacon is much cheaper than installing wires in industrial zones, for which you might need to shut down processes and perform security checks.
A disadvantage is that it’s a little less accurate than GPS and it requires minimal infrastructure where GPS requires none.
An alternative approach to locate a device using BLE is working with BLE gateways. Gateways are installed on fixed locations and act as a location marker. These devices are used to localise tracking devices that are not (necessarily) connected to the internet. The tracking device transmits a BLE signal which is received by the gateway. The gateway will forward the unique identifier of the transmitting device to the cloud allowing it to be localised.
BLE localisation accuracy relies on determining the distance to a fixed marker. There are different approaches. The device can take over the location of the closest marker or it can estimate distances to all markers it can reach and do a triangulation to determine a position.
There are also different techniques to determine the distance between two devices over BLE. The simplest is using the signal strength of the received signal but it is also possible to measure angles or calculate the time-of-flight.
The combination of these techniques will determine the accuracy of the location determined over BLE. If only one marker is used and this marker is selected based on RSSI (Received Signal Strength Indicator) the result will be less precise compared to combining different markers with more precise location estimations like time-of-flight. Signal strength can be affected by reflections or absorption, resulting in a deviant calculated distance.
Bluetooth Low Energy in short
- Accurate indoor / outdoor (depending on infrastructure)
- Low energy use (1/15th of GPS)
- Minimal wireless infrastructure required
- Infrastructure required
Wi-Fi positioning taps into wireless local area networks (WLANs), which are networks of devices that connect to a specific radio frequency, usually 2.4GHz or 5.0GHz. The Wi-Fi device transfers signals for a range of up to one hundred meters, which means Wi-Fi can cover both indoor and outdoor sites. A tracking device will sniff for nearby Wi-Fi access points (APs). By determining the unique identifier of the APs, the MAC address for example, a position can be determined. Local or public databases provide the link between observed MAC addresses and geolocation.
Tracking devices only sniff for Wi-Fi signals, they do not have to connect to the Wi-Fi. Therefore Wi-Fi positioning also harnesses Wi-Fi networks that you don’t own or can’t access. For instance, as a commercial trailer passes through an urban center, it will drive through hundreds or thousands of Wi-Fi networks.
Good to know is that Wi-Fi has a low energy usage. The accuracy depends on two major factors: density of the access points, and the accuracy of the database. There is a risk of false database entries which results in false positions. Wi-Fi does not require additional infrastructure. As mentioned above, your Wi-Fi device can track information about networks in the area. Keep in mind that this might require paid service or you need to know the local infrastructure network.
Wi-Fi in short
- Accurate (depending on availability)
- Low energy use (1/10th of GPS)
- Might require paid service or known local infrastructure network
- Not for rural areas where no WiFi infrastructure is available
Location can also be determined by using a service provider’s network infrastructure. The accuracy of network-based techniques can vary. This is both dependent on the concentration of base stations and the implementation of the most up-to-date timing methods. A technique used by different network providers is network triangulation. This means that you can determine the location of a point by forming triangles to it from known points. To use a service provider’s network infrastructure your tracking device will be equipped with a module of the service provider.
Of all the geolocation technologies discussed, network-based geolocation requires the least energy. The accuracy of this positioning technique depends on the network and the density of available base stations (usually higher in an urban environment compared to a rural environment) and can vary a lot.
Network-based geolocation in short
- Works everywhere indoors and outdoors
- No additional energy consumption
- No infrastructure required
- Accuracy depends on the network
The real strength lies in combining geolocation technologies
Each technology has its strengths and weaknesses. The real strength lies in knowing when to use which technology to ensure both minimal energy consumption and maximum data accuracy.
Each project evolves over time and so do the needs for asset localization. Balancing this energy use and correct usage of geolocation technologies is a key aspect of our solution. This is achieved by combining intelligence on the device and intelligence on the platform, adapting over time.
The choice of geolocation technology can also vary per location. In your factory you might require 10 meter accuracy while at a supplier you do not require this precision. The ability to add additional infrastructure only where you need more precision adds flexibility.
In some places it is worth to take the extra costs of additional infrastructure while on other locations you want to keep costs to a minimal because there is no added business value.
Geolocation should be dynamic, allowing you to use the optimal technology at each location. In Figure 4 below, you see the example of a tracking device that first tries BLE localization. When this would fail it falls back on GPS, if that also fails there is still the option for a Wi-Fi or even network location. Regardless the physical location (outdoor/indoor, rural/urban, …), the tracking device will always find a technology to localize itself with the highest possible precision.