When calculating excavation, what is 'HI' an abbreviation for?

In the context of excavation and construction surveys, 'HI' stands for Height of Instrument. This term refers to the elevation of the survey instrument (typically a level) above the reference point or benchmark. The height of the instrument is crucial for accurately determining elevations at various points during excavation and construction work.

Understanding the height of the instrument allows surveyors to calculate the necessary adjustments for accurate leveling and ensures that all subsequent measurements are precise in relation to the established benchmark. It is essential in establishing a proper reference line for any excavation project, enabling the team to effectively gauge the depth and elevation required.

While the other options might sound plausible in different contexts, they do not specifically relate to the standardized terminology used in surveying and excavation.