Geodesy is usually defined as the study of Earth’s shape and its gravitational field. While Earth’s gravity variations in space or time would not likely be of interest to most geomorphologists, the shape of Earth’s surface is clearly relevant. A few decades ago, these data might be presented as a simple topographic map. However, quantitative descriptions of Earth’s surface are commonly referred to as digital elevation models (DEMs). The techniques that generate DEMs have become sufficiently precise that they can describe and detect changes of the Earth’s surface at the decimeter to centimeter level, and sometimes at the millimeter level, although this may require sophisticated geo-referencing. Moreover, these techniques are sufficiently cost-effective that their repeat times, which effectively determine their change detection capability, can range from a few years to a few minutes.

No review is complete, and ours is no exception. Here we focus on four modern geodetic techniques that are currently used to produce high precision DEMs, in many cases sufficiently precise to enable change detection on useful time scales: light detection and ranging, sometimes called laser imaging, detection and ranging (lidar), interferometric synthetic aperture radar (InSAR), terrestrial radar interferometry (TRI), and structure from motion (SfM). Except for TRI, which is restricted to stable ground-mounted plat- forms, the instrumentation can be hosted on a variety of platforms, including satellites, piloted aircraft, and unoccupied aerial vehi- cles (UAVs) (Fig. 1). In some cases, construction of the DEM may involve merging of two or more data sets, with associated challenges in geo-referencing to a common datum (reference surface).

Here we give a brief review of each of these four technologies, with a few example applications, with implications that can be readily applied to tectonic geomorphic and associated studies. Since SfM is a relatively new technique, that section has somewhat more detail than the others. For each of the techniques, we have tried to reference a broad range of literature so that interested readers can delve into these subjects in more detail.