There are two main categories of dating methods in archaeology: relative dating and absolute dating.
Relative dating includes methods that rely on the analysis of comparative data or the context (eg, geological, regional,cultural) in which the object one wishes to date is found. This approach helps to order events chronologically but it does not provide the absolute age of an object expressed in years. Relative dating uses many techniques, but the most common are soil stratigraphy analysis and typology.
Absolute dating includes all methods that provide figures about the real estimated age of archaeological objects or occupations. These methods usually analyze physicochemical transformation phenomena whose rate are known or can be estimated relatively well. This is the only type that can clarifying the actual age of an object. Absolute dating methods mainly include radiocarbon dating, dendrochronology and thermoluminescence.
Archaeologists don't just look at objects and give opinions of age. Dating is done carefully with scientific instruments, computer analysis, professional standards and peer review.
As in all fields of science, in archaeology there have been amazing advancements in knowledge, databases, chemistry, imaging, instrumentation and analysis over the past 30 years. The quantity and quality of data collection and artifacts is exploding. Clear pictures of the past are rapidly emerging.
It is now possible to have greater accuracy and confidence in scientific dating because there are so many testing methods and so much data. Testing can be done on the same object with different methods, and accuracy is assured when all reveal approximately the same age.
Arial imaging is not a way of determining age but is a way of identifying high potential excavation sites which have an abundance of structures, fossils and artifacts. The result is more and better sites and objects to study, in less time and at less cost.
CT scans are used to X-ray blocks of sandstone and limestone to see if what's inside is worth chipping out and to help avoid damage in the process. This improves efficiency and quality.