Radar altimeters send pulses of radio waves straight down to Earth and measure how long they take to come back. Because radio waves travel at the speed of light, turning travel time into distance is straightforward. Combined with precise information about the satellite’s orbital position, the height of the sea surface, ice sheets, rivers, lakes, wetlands, or land can be tracked over time. Their purpose is not to generate images like SAR but produce a 1D/narrow 2D track of highly accurate height measurements.
