Definitions of "baseline study" on the Web:

* A model of evaluation which attempts to show that some intervention produced a gain in organizational performance by comparing a measure of performance after some action is taken to a measure of performance before the action. (The intervention is usually considered successful if the measurements taken afterwards exceed the baseline data by a statistically significant amount - assuming that the conditions for the two measurements are the same.)
www.ndu.edu/irmc/elearning/primer/glossary.htm

* (1) For a geographic area where human activities potentially affecting the environment are proposed, a study is undertaken to describe the existing conditions and trends. This description of key ecological system components and their functional relations through time provide a reference "baseline" from which the effects of the proposed action may be predicted. ...
fwie.fw.vt.edu/rhgiles/appendices/glossb.htm

* a description of existing conditions to provide a starting point against which progress can be assessed or comparisons made
www.mos.gov.pl/mos/publikac/Raporty_opracowania/manual/glos...