Introduction to Radar Remote Sensing (Page 8):

Color Radar Images

On page 6, we saw that a radar image is a black and white view of the Earth. So, how can we produce a color radar image?

The answer is to this question is to use the same method as the one used for visible and infrared images (see our "Multispectral Imager" for more details!). We can combine radar images that have been taken either at different wavelengths or different polarizations, such these observations are all affected in slightly different ways by the same surface.

It would take too many pages to show you all of different examples of radar images of our study area of Kilauea Volcano, so what we show below are three different views that highlight the effects of different wavelengths and polarizations. Recognize that it would also be possible to show images obtained at a number of different incidence angles, or data obtained when the soil has different water contents (i.e., different dielectric constants).

HH Polarization

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VV Polarization

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HV Polarization

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It is important to know that the colors in the three images above signify that not all of the surface responds in the same way to radar energy of different wavelengths. If all of the lava flows reflected energy at the same amount, each image would be just one constant color. These different colors are due to variations in the roughness of aa and pahoehoe lava flows, the amount of ash on their surfaces, and the age of the rocks.

Also, if you take a close look at the three images, you will see that the distribution of colors is different in each of them. Because we are looking at radar data collected at three different polarizations, this difference between images tells us that the surfaces have slight variations in their shapes. If we were doing a detailed study of the way that the lava flows were formed, this type of polarization information would be very useful, but it is not as important as the variation with wavelength.

Have you seen our other Remote Sensing Tutorial on Visible and Infrared Images ?

Author: Pete Mouginis-Mark

Copyright by P. Mouginis-Mark

Curator: Lori Glaze