Which vertical datum was established in 1929?

The National Geodetic Vertical Datum of 1929 (NGVD 29) is the correct answer because it was officially established as a vertical datum for the United States in 1929. This datum was created to provide a consistent reference point for measuring elevations across the country, based on a network of benchmarks and a defined mean sea level. The NGVD 29 has served as an essential reference for topographic mapping, construction, and various engineering projects related to elevation.

In contrast, the World Geodetic System 1924 is a global reference frame primarily focused on horizontal positioning, and it does not pertain specifically to vertical measurements. The North American Vertical Datum of 1928 is an earlier system that predates NGVD 29 and was used for similar purposes but was ultimately replaced by NGVD 29 due to advancements and refinements in measurement techniques. The Normalized Geodetic Datum 1929 is not a recognized vertical datum, making it irrelevant to the question at hand. Understanding the importance of NGVD 29 in the evolution of vertical datums provides clarity on its foundational role in GIS and geographic studies.