Last week we looked at how GPS and RFID work, today we'll compare and contrast the two technologies and see how the strengths of each can be used to compensate for the limitations of the other.
The global range of the global positioning system is its greatest strength. GPS enabled devices can be tracked all over the world with no additional equipment necessary as the GPS satellites are already positioned overhead. However, reliance upon satellites yields the system's greatest weakness - inaccuracies or failure to determine position due to obstacles or signal reflections. The presence of buildings, mountains, or dense foliage can serve to block GPS satellite signals; operating in canyons or indoors can be very difficult or impossible. Signals can also reflect off of nearby surfaces causing the GPS device to receive too many mixed signals resulting in inaccurate locations or failures.
One of the biggest strengths of RFID is its customize-ability and flexibility. The different types of tags can address nearly all necessary purposes. Lower-cost passive tags require closer read ranges but can be teamed with readers positioned at entry points or along conveyor belts to log the tag's movement, while higher cost, "always on", active tags can be placed on items throughout a warehouse or stockyard for constant monitoring. The weakness in RFID is the reliance upon a reader. While there are handheld readers available, meaning the position of the reader is not required to be fixed in space, the overall scale of an RFID operation, due to it's reliance upon readers and limited tag read-ranges, is very much "local".
The other major difference between RFID and GPS is that an RFID tag transmits to the reader information stored on its chip. RFID tags have been combined with other monitoring equipment such as thermometers or medical equipment in order to transmit not only the tag's location, but various characteristics of the tracked item (such as temperature or vital signs).
By creating tags with combinations of RFID and GPS chips users are able to get the global tracking ability of GPS while outside the local zine then utilizing RFID for indoor or local position tracking possibly combined with other status measurements.
There are many unique ways in which this combination may manifest itself. There are combination tags developed where the tag is set to operate as RFID by default, switching to GPS once the item has left the facility "exit point". One company has a system where GPS is used to monitor an item's location in an open air stock yard. When an item needs to be moved a reader mounted on the forklift collects data on the item's exact contents. Then there is the unique example we cited in the opening of Part I, where Macy's is testing a system where GPS detects a user's approach (via smartphone) and then launches an app with advertisements to entice the customer to enter the store. Once in the store RFID systems detect customer's locations and provide promotions specific to the customer's immediate vicinity.
There are many possibilities for these relatively new GPS and RFID combined tags. With the way these two technologies uniquely balance each other there are surely many more applications to come.