Geodesy is the study of big areas of land such as countries or continents. It is like mapping but is used to measure the size, shape, and gravity of these big pieces of land. People have been studying geodesy since ancient times. It was used to measure the distances between cities and countries and make sure they were in the right place. Geodesy was an important part of sea travel. People used it to figure out where they were, how to get where they wanted to go, and how big an area was when they arrived. People also used geodesy for things like building bridges, roads, and towers. By understanding how the land was shaped, engineers and builders could build things that were strong and safe. Geodesy has continued to grow and change over time as technology has improved. Today, geodesy is used for many things, like measuring the height of mountain ranges, helping to make more accurate maps, and predicting things like earthquakes and floods.