Module 8 - Thermal Imagery

Every day objects such as rocks, water, soil, vegetation, cars, and people emit thermal infrared radiation. The Stefan-Boltzmann law explains the relationship between these objects' temperatures and the energy they emit; and that is that objects with higher temperatures emit more. Thermal imagery illustrates just that. Some of the more popular uses of thermal imagery include: residential and commercial heat-loss insulation studies, firefighting resources for emergency situations, and detection machinery for wars. (Jensen)

For our lab exercises, we learned how to convert multiple layers of multispectral images obtained from USGS (which contained thermal data), by using the Composite Bands tool in ArcMap (Data Management tools > Raster > Raster Processing); and by using the Layer Stack tool in ERDAS Imagine (Raster tab > Resolution group > Spectral). By combining these layers, we made it easier for ourselves to analyze patterns and features in the thermal infrared imagery.

For our lab assignment, I identified a vegetation type, "mangrove trees" surrounding Guayaquil city in a region of Ecuador. I began my analysis by looking at each individual band separately in ArcMap under Properties > Symbology > Stretched. I found that Band 4 illustrated the greatest, crispest difference for vegetation verse urban verse water features. To best differentiate among the temperatures of these features I used the band combination R6, G4, B7, as well as manipulated the breakpoints in the histogram to contrast the mangrove trees (seen as hues of bright, neon green) from the highly-dense urban areas (depicted as neon pink).