Summary of Remote sensitive images analysis
Remote sensitive images analysis is commonly using artificial
neural networks. In particular convolutional neural networks (CNN) getting more
and more attention in remote sensing images classification. A class of CNN-based deep neural networks, commonly used for the analysis of visual images
recognition and classification, is used exclusively in images made up of 2D and 3D
dimensions. An RGB image is typically captured using three different
wavelengths, about 610 nm for red, about 550 nm for green, and about 460 nm for
blue. The hyperspectral image, on the other hand, can be captured using a
wavelength range of 400-1000 nm with a resolution of 400 spectral channels.
Processing within hyperspectral remote sensing data is multispectral data and
challenging in the hugeness of remote sensing data processing, as many spectral
bands contain large amounts of data. With the continuous increase in
application requirements and the continuous maturation of remote sensing
classification and detection technology, the spectral resolution of
hyperspectral images is continuously improved, and the spatial resolution is
also gradually improved. Since an RGB image consists of only three spectral
channels, classifying spatial information based on a widely used machine
learning model implies that it is a drawing of a conventional neural network
(CNN). For hyperspectral images, it may have several hundred spectral
dimensions, but it is more interesting to attention to spectral dimensions than
spatial information. At present, both spaceborne and airborne hyperspectral
sensors have high resolution, which provides a good basis for the
classification and recognition of ground materials. At the same time, the
“Hughes phenomenon” and band redundancy are still two important challenges in recent
years and even in the coming decades. Relevant concepts in computer vision are
introduced with the task of hyperspectral image feature extraction and a deep
learning framework is used to combine visual features with deep abstract
features, and efficient feature learning methods are used to improve the effect
of classification.
Introduction
Remote sensing is a broad technology developed in the 1960s that uses a variety of sensing devices to detect and acquire various ground views over long distances. Remote sensing is remote sensing, i.e., collecting various data or detecting or recording the exterior of an object or position by the emission, reflection, radiation, etc., of electromagnetic wave beams from a distance. The hyperspectral remote sensing image (Hyperspectral Remote Sensing Image) is often referred to as hyperspectral imaging, and its classification work is very important in the fields of defense, agriculture, climate, and marine surveillance. In this chapter, the principles and background of remote sensing and hyperspectral remote sensing technology were first introduced. Then hyperspectral image introduced the relevant research basis of classification, and the hyperspectral image presented the difficulties and challenges of the current work of classification.1.1
Motivation
1.2 Hyperspectral remote sensing
Hyperspectral remote sensing images are composed of
many pixels that represent the characteristics of the earth's surface object each
pixel represents the surface feature of hundreds of wavelengths of solar
radiation. Hyperspectral imaging (HI) contains detailed earth surface
information with high resolution at both spatial and spectral levels. The
hyperspectral images obtained have a wide range of applications. In this
section, the principle and research background of remote sensing technology is
first introduced. Then, the relevant theories of hyperspectral remote sensing
technology and the characteristics of hyperspectral images are explained to
provide accurate research sources and application values for the subsequent
classification of hyperspectral images.
1.2.1 Remote sensing technology
Feature of remote sensing
images Remote sensing images is featured by their spectral, spatial,
radiometric, and temporal resolutions. Hyperspectral imaging is an image
produced by reflecting electromagnetic energy, known as imaging spectroscopy.
In hyperspectral imaging, hundreds of narrow-bands, continuous spectral bands
from the same region are displayed in a range of visible to infrared
wavelengths. These images are combined into a three-dimensional (x,
y, λ) hyperspectral data cube for processing and analysis. Here x and y
represent the two spatial dimensions and λ represents the spectral dimension of
the image. In the current human use of remote sensing technology, remote
sensing usually refers to the detection and classification of earth substances
based on transmitted signals through the use of sensors carried by satellites
or aircraft, including information about the surface, atmosphere, ocean, and
other materials data information[1]. In recent years, remote sensing technology has
played a vital role in hydrology[2], ecology[3], geology[4], and Marine science[5].
Remote
sensors collect data by detecting energy reflected from the earth. These
sensors can be on satellites or mounted on aircraft. They detect the natural
energy reflected or emitted from the Earth's surface. The most common source of
radiation detected by passive sensors is reflected sunlight. The data captured
by remote sensing technology is called remote sensing image and is feature by
the resolution in terms of space, spectrum, radiation and time[6]. Temporal resolution refers to the measurement of
satellite or aircraft overflight frequency, and its acquisition method requires
repeated acquisition of a specific area in a specific task [7]. Specific resolution refers to the measurement of
pixels in remote sensing images, which are generally compatible with square
areas within 1000 meters from the ground. Spectral resolution refers to the
measurement of wavelengths in different frequency bands and is related to the
number of bands covered by the acquisition device. Radiation resolution is a
measure of the sensor's ability to distinguish between 8 to 14 bits of
radiation of varying intensity. Remote sensing is the collection of information
about an object or event without actual physical contact, as opposed to on-site
surveillance or field reconnaissance. This often requires the use of airborne
sensor technology, such as aircraft and satellites, to detect and analyze
things on the ground, usually above the surface. Through these correction
means, the "distorted" image can be transformed into accurate actual
data[8]. Technologies and techniques used in remote sensing
include: Conventional radar, laser and radar altimeters, Light Detection and
Ranging (LIDAR), stereographic image comparison, multispectral and
hyperspectral imaging
1.1.1 Hyperspectral remote sensing technology
Advances in sensor technology and spectroscopy have
led to high spectral resolution images called hyperspectral images.
Hyperspectral remote sensing is not generated directly. Based on remote sensing
technology, combined with the continuous improvement of hardware technology and
imaging equipment, researchers' requirements for remote sensing applications
are also growing. As shown in Figure 1.1, the band of remote sensing image is
gradually evolving from wide to narrow until the band range almost reaches the
nanometer level, and the hyperspectral remote sensing technology is becoming
more mature[9]. Hyperspectral remote sensing technology can
simultaneously use dozen’s or even hundreds of extremely narrow Spectral bands to collect data, capture more
data and provide more valuable information[10].
Advances in sensor technology and spectroscopy have
led to high spectral resolution images called hyperspectral images.
Hyperspectral remote sensing is not generated directly. Based on remote sensing
technology, combined with the continuous improvement of hardware technology and
imaging equipment, researchers' requirements for remote sensing applications
are also growing. As shown in Figure 1.1, the band of remote sensing image is
gradually evolving from wide to narrow until the band range almost reaches the
nanometer level, and the hyperspectral remote sensing technology is becoming
more mature[9]. Hyperspectral remote sensing technology can
simultaneously use dozen’s or even hundreds of extremely narrowspectral bands to collect data, capture more
data and provide more valuable information[10]. The
concept of hyperspectral remote sensing began in the mid-1980s and to date has
been used primarily by geologists for mineral mapping[11]. The United States occupies a relatively leading
position in this field. Hyperspectral remote sensing imagery is often referred
to as hyperspectral imagery, and its classification work is very important in
defense, agriculture, climate, and ocean monitoring. Spectroscopy is the study
of light emitted or reflected from matter and processed into wavelength energy.
Spectrometers using several thousand or even thousands of detectors can narrow
the range of broad wavelengths of spectral measurements of bands than 0.01
microns, usually at least 0.4 to 2.4 micrometer. Spectroscopy is spectral
reflectance, which is the ratio of event strength as a function of wavelength.
The hyperspectral camera carried by the satellite is the world's first visible
shortwave infrared instrument that considers both wide coverage and broad
spectrum. It has a width of 60 kilometers and a spatial resolution of 30
meters. It can reach 330 spectral color channels in a range of visible light
colors from the shortwave infrared spectrum. This color range is about 9 times
larger than that of a normal camera and the number of color channels is about
100 times larger than that of a normal camera, the subtlety of the color width
is equal to one-thousandth of the thickness of a paper[12].
0 মন্তব্য(গুলি):
একটি মন্তব্য পোস্ট করুন