DCHP-1 Online
flying level 
See 1829 quote.
- 1829 . . . we were enabled to take, what is called in surveying a flying level, which is a rough guess to a foot, more or less, of the rise or fall of the country above any fixed data.
- 1829 [We took] what is termed flying levels through the dark woods. . . .
- 1903 We were taking a flying-level between Rafting Bay and the Rideau--a distance of about four miles.
- 1829 . . . we were enabled to take, what is called in surveying a flying level, which is a rough guess to a foot, more or less, of the rise or fall of the country above any fixed data.