Image Processing Reference
In-Depth Information
Figure3.19 Visible and microwave images of Venus. (LeftimagecourtesyofCalvinJ.
Hamilton,rightimagecourtesyofNASA)
highest mountains on the planet are grouped together. This radar image of Venus
demonstrated for the first time that the geology of Venus has some similarity to the
geology of earth, as thetrough-and-ridgestructure seen on many parts of Venus
looks exactly like trough-and-ridge structures seen on the Pacific and Atlantic
Ocean floors. Note that the surface of Venus is only partially illuminated by the sun
in theGalileoimage, while the entire surface of Venus is illuminated and imaged
by microwaves in theMagellanimage.
Magellanwas able to image small surface features of Venus in addition to
large-scale formations. Figure 3.20 is a radar image of Maat Mons, a volcano 8
kilometers in height imaged at an oblique angle to the surface. Note the variations
in the brightness of the image—these are caused by differences in the surface
texture. Texture has a strong effect on the reflectivity of a surface to microwaves.
As with Fig. 3.19, the choice of colors was suggested by theVeneracolor video
data, although here the brightness is proportional to the signal return strength rather
than the relative altitude of the surface.
Small-ScaleImagingRadar
Radar imaging can also be applied to imaging applications involving everyday
objects and distance scales. Developments in high-speed data acquisition
electronics at Lawrence Livermore National Laboratory have led to a novel type
of radar called MIR, an acronym that stands for micro-power impulse radar. This
short-range radar, which operates in the 15-cm microwave band, can see through
opaque materials like soil and concrete, and can create high-resolution images of
buried objects. MIR technology forms the heart of a new type of portable mine-
sensing device that can detect plastic landmines that elude conventional metal
detectors.
The radar uses ultrashort pulses of radio waves to detect boundaries between
materials. A small amount of radio light is reflected at the boundary between
Search WWH ::




Custom Search