There seems to be confusion in the industry about where these descriptions differ.
RFID is a general description of any system that identifies without line if sight. At a cursory glance, RTLS (Real time location System) seems to add a qualitative presentation and timeliness element to data that is collected by RFID.
But ask yourself these questions:
1. Is an RFID system real time if it reports the data immediately? What about all the times it is NOT reporting?
2. If the sensors are shown on a map does that make it a location system? What about all the places where there are no sensors?
Don’t be distracted by the wrapper on the package. The distinction is fundamental and real. It goes deeper, to the underlying capability of the sensing system, not the presentation. It’s about the information that is not easily collected.
Uses one sensor at a time
Records presence near sensor
Answer is binary – a tag IS / IS NOT here.
Uses many sensors simultaneously
Calculates best answer from all sensors
Answer is Qualitative – tag is “about here” represented on a map
Most offerings use one or the other method. But some more advanced hybrid technologies actually merge the two capabilities of both. But fundamentally, an RTLS system should have the requirements of covering everywhere within your scope, all the time. If it does this, whether it uses proximity, time of arrival, or some other method, is more of a nuance than distinction.
Bottom line is:
First identify what are the primary goals of the measurement system.
Then identify the cases where each technology will be right about what it senses, and when it will be wrong.
Your requirements should strike the best risk reward trade-off for you situation.