What are the Advantages of Multi Spectral Satellite Images
Advantages of Multi Spectral/Band Satellite Images
Remote Sensing sensors record earth's reflectance in different wavelength and these received reflectance value are processed to create separate image for each wavelength. The reflectance value stored for different wavelength in different layers, which are also called bands present in that satellite images.
Multi band images also known as
multi spectral satellite images. Multi band image simply define, when more than one band/spectrum and at least three wavelength data recorded by sensor to create composite of satellite images. A sensor can record several wavelength simultaneously and it is completely depend upon sensor characteristics and capabilities.
As
it is already studied that sensor can record earth surface feature in different
wavelength from visible spectrum to infrared spectrum. The reflectance recorded from different
wavelength can be converted in to satellite image.
In general three wavelength
from visible i.e. blue wave length, green wavelength and red wave length,
whereas infrared can be further defined as near infrared, mid infrared, far
infrared and thermal infrared.
So it can be simply explained as capability of
sensor to sense reflectance in to different wave lengths to create multi band or multi spectral images. For example Landsat 7 can record reflectance in seven
wavelengths/bands.
Whereas Landsat 8 can record in eight wavelengths/bands
excluding panchromatic band. LISS-III sensor of IRS series has four spectral
bands and LISS-IV sensor of IRS series can record reflectance in three
wavelengths.
Multi band/spectral analysis is
studying earth surface in different wave length/bands. Multi spectra/band data
are required to create color composite images in the form of natural color
composite and false color composite.
All the image processing tools such as
indices/rationing, principal component analysis, image fusion etc. can be used
only if data collected in multi band. Each band in a multi spectral data
collected through satellite, has unique reflectance values for same area with
the change in wave length.
As reflectance will take place by mutual relation
between incident wave length and material properties phenomenon. So reflectance
may change with the change in wavelength for same earth surface feature. Multi
band/spectral images ensure better and more accurate identification of earth
surface features.
In the below images, three different
images are shared to understand the advantages of multi band satellite images.
First image is showing earth surface
object in grey scale or black and white. It is clearly visible from grey scale image
that, visual interpretation is very much limited due to absence of colors in
image. Identification of object also needs more experience to recognize and
judging significance.
By looking below image which is
prepared using multi band/spectral data, it is natural/true color composite. Identification
of object becomes comparatively easy and accurate in natural color composite.
This image is showing a false color
composite, in which infrared wavelength band is also integrated to create color
composite. It is very advantageous as maximum reflectance of vegetation received
in infrared and if it is not integrated than loss of information in that color
composite. Which ultimate effect the accuracy of information extracted using
satellite image classification process.
Therefore it can be explained that
multi spectral images are very advantageous for extracting information and
facilitate more accurate interpretation and classified thematic maps.
Due to more accurate date creation using
multi band satellite images, it can be used to as input data in many studies such
as urban planning, crop monitoring, forest mapping etc.
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