What Can we See in a Radar Image?
Other parts of Virtually Hawaii show examples of radar images of Hawaii, but let us take a closer look at one example image. These data were collected by a NASA aircraft in 1990 over part of Kilauea Volcano. The black and white image below shows a 24 cm wavelength radar image, taken at an incidence angle of 45 degrees, for an area of the Southwest Rift Zone that includes a lava flow erupted in December 1974.
We have added labels to this image to show features that can also be clearly seen in the set of air photos below of the same area. Often, it is only by looking at visible wavelength data that we can understand the radar image. First, we show air photos that we took from a helicopter flying low over the volcano. We then show (on Page 7) a set of ground photos to further help understand the radar image. What we see is that the radar-bright part of the flow (at pt.1 and pt.2) is an aa lava flow -- which is very rough at this wavelength and so has a high backscatter. At pt. 3 we are standing on a cliff that reflects the radar energy so that it appears as a bright line. We can also see that at pt.s 4, 5 and 6 there is a boundary between one type of lava flow and another. Based on the radar backscatter from each type of flow, we can say that the second type of lava flow is a smooth pahoehoe lava flow because of its low backscatter values.
Go on to Page 7 of this Remote Sensing Tutorial to see some ground photographs at some of these locations.
Author: Pete Mouginis-Mark
Copyright by P. Mouginis-Mark
Curator: Lori Glaze