VISUALIZING AN IMAGE
We will start talking
about satellite images, in this example they are identified by the Category: TM_Image.
An image is similar to a
photograph, which is obtained by a sensor on board of the satellite. The
"Thematic Mapper or TM" sensor on board of the LANDSAT 5 satellite
can get seven different images from the same region, each image is named a
band and they are enumerated 1 through 7. Each band has information about the
amount of radiation reflected by the earth surface, in the electromagnetic
spectrum band. The TM-1 band corresponds to the blue color wave length, the
TM-2 band corresponds to the green color wave length, the TM-3 band
corresponds to the red color wave length, and TM-4, TM-5, TM-6, and TM-7 are
related to different wave length in the infrared spectrum, which are not
visible by the human eye. The SPRING manual describes in more details the
image features. You will have the opportunity to access these information
during this training. Each image corresponds to
an independent layer of information. The layers can be combined, thus the
name Information Layer or IL, which translates this idea where each
layer carries a certain type of information. In this project there are
several images taken from the LANDSAT TM, with a In order to visualize a
color image we need to combine three bands and associate, each of them, to
the basic color system (Red, Green, and Blue). In order to facilitate an
image visualization in color the IL ComposicaoR4G5B3 was generated in
a single band, artificially, using the composition of the three band (TM_3, TM_4 and TM-5), creating
what is called a synthetic image. This color composition is
denominated false color, because it does not reproduce the natural
colors of the objects, associating the LANDSAT bands 5, 4 and 3 to the Red,
Green and Blue colors, respectively.
VISUALIZING A SINGLE
BAND
In order to visualize a
single band (IL) in gray level we can use any of the bands obtained by the
satellite sensor.
VISUALIZING THREE BANDS
IN A SINGLE display
VISUALIZING IMAGES IN
SEPARATED display
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