How has global sea level been measured over the past century?

Over the past century, global sea level has primarily been measured using tide gauge measurements. Tide gauges are long-established instruments that measure the height of the sea relative to a fixed point on land. These devices are placed along coastlines and record the rise and fall of sea levels over time by detecting changes in water surface elevation. The historical data collected from these gauges has been crucial for understanding trends in sea level changes, providing a consistent and reliable record that spans decades.

While satellite imagery and modern technologies have emerged to complement sea level research, they have not been the primary method used throughout the entire century. Ground surveys, on their own, do not provide a continuous measurement of sea level changes and are typically used in conjunction with other methods. Drone technology, being a relatively new advancement, is not historically significant in the context of measuring global sea levels over the past century. Instead, tide gauges have played an essential role in establishing a long-term dataset that has informed climate science and policy discussions concerning sea-level rise.