Any successful tracking solution, whether for people, machinery or materials, needs sensor tags appropriate for their working environment. They need to be resilient enough for the risks associated with location loss, easy to maintain and easy to manage.
The systems involved in their management must also be able to provide or deliver a variety of factors. These include package sizes, shapes, weatherproofing and operating lifetime to allow data to be available from whatever physical situation.
Is it 3D?
First question you need to consider is how accurate do you need this location to be, and can you work with 2D information (like GPS/GNSS systems that usually show you on the earth’s surface) or will you need 3D?
Accuracy to well within a meter is possible should this be required using UWB (Ultra-Wideband) technology. UWB can give this high accuracy location in three dimensions.
Bluetooth LE is used in many sensor tag solutions. Accuracy in a well-designed system should be within 3m. Bluetooth is also supported by a wide range of other devices. This includes smartphones that could be integrated into your tracking system.
You can even use your existing Wi-Fi network to give location to within 15m or so. Plus, many tags include more than one of these technologies (including GPS/GNSS).
Battery and Sensor Lifetime
There are compromises to consider with sensor tag solutions. These include the issue of accuracy, with each situation bringing differing demands on build quality and operating environment. There’s also the issue of battery life and ease of battery charging or exchange.
Many wireless solutions for tag location are Low Power and so a tag using only a protocol such as UWB or Bluetooth could well have a battery life approaching ten years.
High power is required for Wi-Fi and GPS, for example. The same battery is likely to only have a life of a year or less.
As many tags feature more than one technology, demands on power are likely to be high and so you will need to decide whether you will use a system that changes batteries periodically, or uses a rechargeable source of energy. Tags will give a warning on battery life, of course, and most will be designed for USB charging. A widely deployed technology, but if you forget to charge the battery then you cannot track it!
I even saw a presentation last year on tracking assets in a large aerospace manufacturing location where a dedicated UHF radio system was deployed purely to charge tag batteries. With a separate low power radio system for actual location. The risk to business efficiency of losing a tag, and the difficulty in this environment to exchange or charge batteries, justified this additional infrastructure.
There are additional factors to consider for personal tags, regardless of the accuracy required. Many situations where these are deployed are hazardous or at least challenging and require a build quality fit for these environments.
Personnel tags are likely to support many radio technologies, but some may not be appropriate to use in particularly hazardous environments. Specific personnel tags may be the requirement for an emergency call or other communications system. This includes fall or other hard detection, and the use of the tag in wider company systems such as Access Control.
Battery life is less likely to be an issue for personnel tags. Rechargeable batteries may be the preference for both tags that are permanently issued to personnel, or those available on site for more ad hoc use that could easily be stored in a dock with USB charging support.
Location tags are available to meet most use cases and working environments, and you may need to consider that a single solution may well be available to you that could involve a variety of technologies and tag form factors. Key questions you need to answer include:
- Accuracy of location
- Ruggedness and residence of hardware build
- Battery life
- Easy of battery exchange/charging
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