• Summary of Remote sensitive images analysis

     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

    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, 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 is 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.

    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].







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    Attention Mechanism Based Multi Feature Fusion Forest for Hyperspectral Image Classification.

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