LAB EXERCISE USING THERMAL-INFRARED IMAGERY FOR GEOLOGIC MAPPING

Remote sensing is an incredibly useful tool for geologic mapping. Visible-wavelength imagery can be used to track changes in color and texture, while imagery recording wavelengths beyond the visible can detect vegetation, clay, iron and rock type. Students are usually familiar with some remote sensing imagery, but their experience is often limited to imagery taken in the visible part of the spectrum.

To address this limitation, a lab exercise was designed to increase student familiarity with imagery beyond the visible and its application to geologic mapping. This lab exercise has students a) use Thermal-infrared imagery to identify rock types and b) determine the sensitivities of different wavelength regions to geologic characteristics.

In this lab exercise, students use airborne MASTER imagery to explore and identify rock units around Lake Mead in Nevada/Arizona. The MASTER imagery, flown by JPL, has 17m pixels and 50 bands across the visible (VIS), near-infrared (NIR), short-wave infrared (SWIR), and thermal infrared (TIR) wavelengths. This imagery was selected because it has moderate spatial resolution and includes 10 TIR bands.

In the first part of the lab, students learn about the sensitivity of the TIR bands to silicate minerals and use TIR imagery to identify rock types. In addition, they learn that the image analysis techniques (ex. RGB combinations) that they have applied to VIS/NIR/SWIR imagery also work on TIR imagery.

In the second part of the lab, students use imagery from different regions of the electromagnetic spectrum (VIS/NIR/SWIR/TIR) to determine characteristics of the various geologic units, such as color, rock type and presence/absence of clay and iron. Students then compare and contrast the geologic units to determine which spectral regions are best used for detecting the various geologic characteristics. Geologic units in this region include sandstone, limestone, basalt, gypsum and river gravels.