Applications ofICESat‐2Photon Data in the Third Pole Environment

Abstract

Elevation information plays a significant role in Earth Sciences as it enables interpretation of the data in three-dimensional (3D) space, especially when the landscape of the study area contains rugged or irregular topography. Topography influences the Earth's surface processes that include geology, hydrology, climatology, and human settlement patterns. The Himalayas, a large mountain belt, are the result of topographic expression from the interplay between tectonic activities, climatic fluctuations, and Earth surface processes. Termed as the third pole, the Himalayan region hosts numerous glaciers, peaks, valleys, rivers, and has a profound role in the “water-ice-air-ecosystem-energy-human” interactions related to most parts of the South Asian countries. Certain Earth system processes of Himalayan mountains act as a climate proxy and thus, long-term studies about the Himalayas provide patterns of climate change. Elevation information is a critical need to investigate a range of surface processes in the rugged terrains of the Himalayan region. The availability of the void-filled global digital elevation model products has paved a better way to integrate remote sensing methods with 3D models. Data from multi-view optical satellite images and Synthetic Aperture Radar (SAR) satellites have been commonly used to understand the elevation component for the study areas that contain rugged topography. However, research results show that there exist certain limitations using these sensors while studying mountainous regions due to the presence of large sloped facies. Similarly, the accuracies of void-filled global digital elevation models differ significantly from the true heights. The recent Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) is the latest addition in space-borne laser altimetry missions launched by NASA and hosts a solo sensor, namely ATLAS, that produces height measurements from surface reflected photons for every 0.7 m along-track direction. The resultant data are conducive to quantify the heights over various surfaces like glaciers, sea ice, water-bodies, land, and canopy. This chapter attempts to demonstrate the applications of photon data from the ICESat-2 laser altimeter for various strategic needs in the Himalayan region. The applications include retrieval of topographic profiles over rugged topography, hydrological profiles, water surface, and canopy height detection, lake ice phenology, and refining the existing elevation models using the heights from surface reflected photons of ICESat-2.