What does the North American Datum of 1927 use for its calculations?

The North American Datum of 1927 (NAD27) uses a combination of measurement units for its calculations, primarily relying on feet and varas. This datum was established to provide a consistent framework for geographic and geodetic measurements across North America. Feet are commonly used in the U.S. survey system, while varas are traditional units used, particularly in areas influenced by Spanish land grants. The integration of these units allows for accurate representation and reference of land measurements used in surveying practices of that era.

This choice reflects the historical context of land measurement in the United States, where feet and varas were prevalent. Consequently, the other options do not accurately represent the units employed by NAD27. Kilometers and centimeters pertain more to the metric system, which is not the focus of NAD27. "Only feet" excludes the use of varas, which were significant in certain regions. Lastly, acres and hectares relate to land area measurements, not used for the fundamental datum calculations themselves. Thus, the combined use of meters, feet, and varas is the correct context for NAD27's calculations.