Advancements of Geodetic Activities in Nepal: A Review on Pre- and Post-2015 Gorkha Earthquake Eras with Future Directions.

From celestial objects to every feature on Earth, geodesy provides a reference frame and is the foundation for surveying, mapping, and other geoscience activities. In Nepal, geodesy was officially introduced after 1924 to prepare the topographic map series. Although the previous geodetic project occurred with foreign assistance, Nepal is using national resources to conduct milestone projects such as the re-measurement of Mount Everest height in 2020 and the ongoing LiDAR survey of western Terai. Taking the 2015 Gorkha earthquake as a reference, this paper reviews the past and present geodetic activities in Nepal. It presents the history of conventional Nepal datum as a horizontal datum and Indian mean sea level-based vertical datum, and modern satellite geodesy works on the Himalayas. Considering recent earthquakes, continuous crustal motion, international and global compliance, and increasing demand for precise positional accuracy from the users and stakeholders, this paper discusses future directions to build, establish, maintain, and operate modern terrestrial, height, and gravity reference systems and frames. This paper consolidates many reports and experiences from Nepal and will serve as useful documentation for newcomers whose interests align in geodesy and Nepal. [ABSTRACT FROM AUTHOR]