Idaho Airships, Inc.

Here are some deliverables from our recent aerial thermography assignment over a site of suspected archaeological importance near the Snake River in central Idaho.

Working with our sister company RedLens Thermography we were assigned to determine whether or not there was themographic evidence of archaeological value in a remote plain near a perennial water source.

Our first step was to image in the visible band at extreme resolution-less than 1 inch per pixel. This was accomplished to generate a visual foundation for identifying thermal signatures of particular features, which are not always easily recognizeable and may present cognitive challenges even when georeferenced.

The following display is constructed using a 417 MegaByte mosaic of sub-inch pixel non-orthorectified orthogonal images. This type of imagery is valuable in its own right for archaeological investigations: for example, footprints are easily resolved along the side of the road in various places.

I’m not teasing about the footprints…

Our second step was to produce an orthographic thermal mosaic of the same area just after sunset. The challenge is that thermal cameras simply cannot match visible band cameras in resolution or clarity-however, the features we were searching for would have been of sufficient size to appear in the thermal collection at our particular configuation. Specifically, densly compacted trails would be several inches wide-at a minimum-and therefore discernable with the calculated resolution of the thermal flight (with all respect to the Nyquist Frequency).

This display demonstrates a colorized thermal overlay and a monochromatic (black & white in this instance) overlay you may manipulate in two ways. Use the buttons to select either the colorized or monochromatic overlay, then use the slider to vary the opacity of whichever overlay you’ve enabled. It is easy to see that the overlays register very well with the features in the visible band base image.

Note that the densely compacted soil of the road is aggressively radiating its thermal load acquired during the day-it registers much warmer than its context. Various other features show differential thermal character as well-the very brightest yellows (especially near the center of the image) represent rock outcroppings that had been in sunlight even after the rest of the area was in shadow. It’s especially interesting to note that tracks of insubstantial traffic (i.e. a single track or area of multiple tracks where the soil is simply distrurbed) do not offer a distinct thermal signature-only those which have endured protracted compaction.

Not all thermographic assays are so easy to interpret. For examle, in this case there is little concern with reflection.

One final note-with thermographic imagery each pixel contains data about the temperature value that the pixel represents. RedLens also has the ability to register each pixel to a Latitude and Longitude value…but in this case, the location of our subject is somewhat sensitive. We also have the ability to drape thermographic imagery over DEMs and TINs.

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