D7 Geological Remote Sensing

Topic

Geological remote sensing encompasses a suite of methods for gathering information about the terrain from airborne or satellite platforms, without direct contact with the surface under study. Its geological applications include generating high-resolution digital elevation models for geomorphological analysis and fault mapping, detecting specific minerals via hyperspectral spectroscopy, measuring ground deformation using radar interferometry techniques, estimating the gravitational field from gravimetry satellites, and detecting thermal anomalies in volcanic areas.

High-resolution digital elevation models—obtained through airborne laser scanning with a vertical resolution of one to two meters—have revolutionized active fault mapping; it is possible to map a fault trace obscured by dense vegetation by stripping away the canopy from the airborne point cloud, thereby visualizing the bare-earth model beneath the vegetation.

A satellite radar formation-flying mission—consisting of a pair of coordinated satellites—produces global digital elevation models with a horizontal resolution of twelve meters and a vertical resolution of less than two meters, derived from radar interferometry between the images captured by both satellites.

Hyperspectral spectroscopy, which captures images across dozens or even hundreds of contiguous spectral bands, enables the identification of specific minerals based on the unique absorption signatures they leave in the short-wave infrared range; clays, carbonates, sulfates, and iron oxides can thus be identified directly from the air or space, with direct applications in mapping hydrothermal alteration, mineral exploration, and fault zones. Finally, infrared thermography detects temperature anomalies on the surface of volcanic and hydrothermal areas with a resolution ranging from one-tenth of a degree to a full degree, thereby—along with the previously described digital elevation models and hyperspectral spectroscopy—completing the suite of techniques used in geological remote sensing to study the terrain without the direct contact mentioned at the beginning of this description.

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