Dendrochronological studies depend on accurate dating of tree-rings. This is achieved through crossdating of tree-rings by examining common patterns of interannual variation in wood anatomy among many tree-ring series. Careful visual examination of the tree cores or cross-sections is the foundation of good crossdating. However, statistical tools have been developed to provide an independent means of assessing the consistency of these patterns among tree-ring series. These tools are particularly useful when many tree-ring series are being compared at once. The most commonly applied statistical tool for crossdating is COFECHA. COFECHA was developed in the early 1980s by Richard Holmes. The version provided here is provided by the Lamont-Doherty Earth Observatory (LDEO) tree-ring lab and is available for download at their website.
Upon successful crossdating many researchers will want to compare their tree-ring series to identify common patterns of growth and in some cases will want to average multiple series. To do this requires standardizing the tree-ring time series. Ed Cook developed the program ARSTAN to develop standardized tree-ring chronologies based on robust time-series statistics.