Dictionary.com
definitions

stadia

1
[stey-dee-uh]
noun
  1. a method of surveying in which distances are read by noting the interval on a graduated rod intercepted by two parallel cross hairs (stadia hairs or stadia wires) mounted in the telescope of a surveying instrument, the rod being placed at one end of the distance to be measured and the surveying instrument at the other.
adjective
  1. pertaining to such a method of surveying.

Origin of stadia

1
First recorded in 1860–65; probably special use of stadia2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for stadia-hairs

stadia

1
noun
    1. tacheometry that makes use of a telescopic surveying instrument and a graduated staff calibrated to correspond with the distance from the observer
    2. (as modifier)stadia surveying
  2. the two parallel cross hairs or stadia hairs in the eyepiece of the instrument used
  3. the staff used

Word Origin for stadia

C19: probably from stadia ²

stadia

2
noun
  1. a plural of stadium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012