GPS vs. UWB: Best Tech for Warehouse Tracking?

Introduction : In the era of Industry 4.0, knowing roughly where an asset is located is no longer enough. Modern logistics demands “Micro-Location”; the ability to pinpoint a pallet, forklift, or worker within inches.

As we know, there are mainly two tracking technologies viz. GPS (Global Positioning System) and UWB (Ultra-Wideband). While both answer the question “Where is it ?”, they are designed for two completely different physical environments.

GPS : A Outdoor technology

It is the technology which powers google maps and trucking logistics. It relies on constellation of satellites orbiting around the Earth to triangulate the position. Let us understand how it works.

• A receiver on a truck or vehicle listens for passive signals from at least four satellites.
• By calculating how long the signal took to arrive, it determines coordinates.

Limitations:

• For warehouse based tracking, satellite signals are relatively weak to penetrate the metal roofs, concrete walls and steel racking systems.
• Even if, GPS signal penetrates inside of building, it has accuracy of about 5 to 10 meters. Based on this information, one can conclude that the item is in the building but can not find which aisle or shelf it it on.

UWB : An Indoor Precision Expert

Ultra-Wideband is an RF technology designed specifically to solve the problems that break GPS, Wi-Fi and Bluetooth in industrial settings. Let us understand how it works in warehouse scenario.

• Instead of satellites, UWB uses a local network of fixed anchors mounted on the warehouse ceiling.
• Tags on forklifts or pallets transmit extremely short radio pulses (with nanoseconds in duration) to these anchors.
• UWB anchors measure time of flight (ToF) i.e. exact time light takes to travel from the Tag to the Anchor.
• Based on the ToF calculation, UWB delivers centimeter level accuracy (10-30 cm).
• Above precision measurement, allows to track exactly which forklift picked up which pallet.

Advantages:

• Offers cm level accuracy of location measurement.
• Warehouses are full of metal (e.g. racks, machinery). Due to this, radio waves bounce-off which creates ghost signals (i.e. multipath interference). As UWB pulses are short and sharp, the receiver can easily distinguish the direct true signal from bounced reflections.

Difference between GPS and UWB

Summary

From the explanation, we can conclude that the choice between GPS Vs. UWB in warehouse asset management depends on use case as follows.

• GPS is better for The Supply Chain : If you are tracking a shipping container crossing the ocean or a delivery truck driving across the country, GPS is the only viable option. It requires no local infrastructure and works globally.
• UWB is better for : Intralogistics (Inside the Walls): For operations inside the warehouse, UWB is the choice as it provides micro-location data needed for various activities such as automate inventory, to prevent accidents by stopping a forklift if worker is too close, to analyze efficiency by creating heatmaps of traffic flow.
• Hybrid is the future: Most advanced smart logistics systems actually use both GPS and UWB. A high value asset might have a tracker with a GPS module for the truck ride and a UWB chip that activates the moment it passes through the warehouse receiving dock. This ensures unbroken visibility from the factory floor to the customer’s door.