In August, as I was looking through our collection of amazing National Park maps to celebrate the National Park Service’s Centennial, I came across a unique piece that I think deserves some special recognition: a 1968 radar mosaic of Yellowstone National Park.
Radar imaging is a major component of the technologies we use to study the earth and collect information about it when observed from afar (a field known as “remote sensing”). In the simplest terms, radar imaging involves radar-equipped aircraft or satellites emitting pulses of electromagnetic radiation from the “radio waves” portion of the electromagnetic spectrum onto the earth’s surface and creating images of the landscape based on the electromagnetic energy that is reflected back to the radar antenna. Bright areas of typical radar images are areas with high degrees of “backscatter,” or strong reflection of radio waves back to the sensor, while darker areas show weaker reflection to the sensor. While there is a wide range of factors that can influence the final image and observed backscatter, radar imaging has been shown to be an effective technique for studying surface roughness, soil moisture, topography, and other physical characteristics of earth.
The radar mosaic of Yellowstone is accompanied by a Department of the Interior news release that describes some of the benefits of radar imaging technology in studying geology and topography:
Radar provides strong shadow effects, thus emphasizing the topography. As a result, earth fissures, faults, joint patterns, lava flows, glacial moraines, stream terraces, and other geologic and topographic features show up more conspicuously than on conventional photography.
Unlike aerial photography, a radar image can be made at night or even through clouds. It shows differences in surface texture thus permitting earth scientists to distinguish between various rock structures, hard bedrock, and soil in some places.
The USGS scientists at Denver, who interpreted a radar “map” of Yellowstone compiled by piecing together 10 flight-strips of side-looking radar images, have readily identified such features as the northwest-trending faults south of the Lamar River; joints south of Obsidian Cliffs; and lava flows near Bechler Canyon.
A closer look at the radar image shows the geologic features identified in the report.
While radar imaging for ground mapping was first developed for military applications during World War II, the technology was still largely in its infancy in 1968 when this radar mosaic of Yellowstone was created. It would be another decade before the first spaceborne imaging radar satellite (Seasat) was launched in 1978. The news release accompanying the radar mosaic of Yellowstone touts the image as an “experimental product” of high scientific value that would be used to help promote future studies of the earth using orbiting satellites.
The technological sophistication of this radar mosaic may be lacking in comparison to the remote sensing technology of the present day, but I still marvel at this image and at what was possible in remote sensing almost 50 years ago.