What Does HI Mean in Surveying

Written By George Mylne  | CategorySurveying 

In surveying, “HI” means Height of Instrument.  The term is used when:

  1. Describing the elevation or height a total station is above a survey mark that it is set up on, or
  2. The elevation of an automatic/dumpy level based on a known benchmark elevation.

How to Calculate Height of Instrument (HI)

When undertaking a level survey run, to calculate the height of an instrument, the formula is:

Benchmark Elevation + Backsight Observation = Height of Instrument

What Errors Can Cause Inaccuracies in Height of Instrument Reading

There are several systematic and human errors that can cause inaccuracies in the height of instrument reading.  These include:

  • Not having an equal foresight and backsight distance.
  • The level bubble on the dumpy level or staff is out of adjustment.
  • Unstable change point marks.
  • Not having the leveling rods correctly extended on the leveling staff.

About the Author

George has been a surveyor for over 13 years, working across a wide range of projects and industries. In this blog, he shares his experiences and information gathered from his time on mining, civil and surveying projects.