UCL Physics Science Centre Lectures - Space Geodesy- Survey of planet Earth by global satellites

Geodesy is the science of knowing where things are and where they are going on Earth.

Geodesy enables us to define space in an Earth-fixed coordinated system. Without this, there would be no Google Maps (other mapping service providers do exist) or any decent maps at all for that matter. And we would struggle to do Earth science. For example, these days tectonic plate motion is measured precisely using Global Positioning System receivers that are sensitive to ground motion at the level of mm per year! Without Geodesy, this would not be possible.

Geodesy allows us to know the height at the summit of Mt. Everest. But is it 8,848m above sea level? Or as reported by a recent study, is it 8,851m above sea level? And what exactly do we mean by sea level? Why is it that are there some places, on land, like Badwater Basin in Death Valley, USA which are said to be below sea level? How is it that a bone-dry desert can be below sea level? By the end of the talk, the audience will be able to answer all of these questions, and more.

The talk is about how Mathematics (Geometry, Algebra) and Physics (Gravity) are used together to describe the size, shape, orientation, mass, mass distribution (and other properties) of the Earth. And it’s about how, today, we now know all of these facts at an extraordinary level of precision because of observations made by satellite systems on orbit – i.e. technologies brought to us by Engineering. At University College London, our research is helping to improve the quality of the data collected by such satellite systems. We will touch upon this work in the final part of the talk.