Sentence:  The two stars, one at the Pole and the other at the Equator, were essential to both <WSD>orienting</WSD> and dating the structure. Hence the conclusion that the Great Pyramid could not have accomplished its design as a monumental witnessing pillar at any other time, and that the only time when the aid indispensable was possible was B.C. 2170. 
Meaning of the word marked with <WSD> tags:  To determine which direction one is facing.