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Understanding the Three Levels of Location: Presence, Proximity and Positioning

To maximize ROI when utilizing the Internet of Things, invest in an RTLS solution that covers all levels of accuracy and multiple use cases, and that will be scalable for future growth.
By Fabio Belloni
Sep 04, 2019

Organizations across a wide range of industries are finding significant value in determining the precise location of a person or object as part of their Internet of Things (IoT) implementations. While all organizations want their IoT solutions to be able to provide an accurate location, what does that really mean? Is location within a meter considered accurate enough? For some use cases, yes. Others require much more precise levels of accuracy, perhaps even down to 10 centimeters.

There are a few different levels of accuracy, and several different ways in which to achieve each level. Finding which solution is the best fit—in terms of both accuracy and total cost of ownership (TCO)—depends on the requirements of the specific use case at hand. Location is important for many industries, but looking at one environment—a warehouse—makes it easy to understand the benefits and use cases the three different levels of location can enable:

Presence detection is the simplest location-based solution—and the least accurate. The goal with presence is simply to determine whether an item is present or not. A common use for presence detection in a warehouse is to determine whether or not an item or a pallet has arrived. Using an advanced location system utilizing Bluetooth technology and the angle-of-arrival (AoA) methodology, a locator at the entrance of the warehouse can act as a "gate" through which tagged items pass.

The locator identifies the tag based on its unique ID, measures the AoA of the tag's signal, calculates the direction of motion for the tag, and determines whether it is entering or exiting the warehouse. Some real-time location systems (RTLS) can further determine presence and provide real-time information within the warehouse because of their long communications range.

Radio frequency identification technology is another choice for presence detection, but RFID has limitations. For example, it requires multiple locators to calculate the direction of motion of tracked items, which can increase infrastructure costs. Also, RFID technology cannot automatically detect if an item has already passed the gate, so there is no way to know if it is still present in the warehouse.

With proximity, the goal is to identify both the presence and location of items, and so proximity solutions typically use a combination of high-accuracy positioning in key areas and low-accuracy presence detection in others. For this reason, proximity solutions are ideal for use cases in which the end customer does not need uniformly accurate coverage throughout the deployment area.

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