It requires a chronograph study of forests in the vicinity, generally done with a microscope.
Dendrochronology also includes a study of surrounding forests and climate, and doing a comparison.
If the source forest was hundreds of miles away, you generally depend on someone else's ring study.
By climate study,I means that it includes temperature, humidity, rainfall, and knowledge of terrain and topography,
as well as the location of where the rings were found.
Basically, it is a scientific system of comparative study and analysis of known factors within a geographic area.
It is a field of study within archeology and anthropology.
Thanks. You sure know your arboreal anthropology!