Which datum was developed after NGVD29 and started in the 1970s?

The datum that was developed after NGVD29 and started in the 1970s is NAVD88. NAVD88, or the North American Vertical Datum of 1988, was established to provide a more accurate reference for elevations in North America. It replaced NGVD29, which had several limitations and inconsistencies due to variations in measurement techniques and geodetic data.

NAVD88 utilized a more extensive and improved network of leveling surveys, allowing it to incorporate advances in technology and methodologies developed during the 1970s. This new datum provided a more reliable vertical reference system, making it essential for applications involving topographic mapping, construction, and emergency management, among others.

By using modern techniques such as precise leveling and geodetic measurements, NAVD88 is able to serve as a key standard for elevation data in numerous applications throughout the United States and Canada, establishing a more uniform and accurate framework than its predecessor, NGVD29. This consistency and precision make NAVD88 a critical component in various fields, including surveying and land development.