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Land Use and Land Cover Mapping of Remotely Sensed Data Using Fuzzy Set Theory-Related Algorithm

Adithya Kumar* and Shivakumar B.R.

NMAM Institute of Technology, NITTE, Udupi, Karnataka, India

Abstract

All bodies, planets, living beings, and inanimate objects emit electromagnetic radiation, and the amount and type of radiation emitted depend largely on their temperatures. Electromagnetic radiation may be emitted by an object or may come from another body and could be reflected by it. There are operational satellite systems that sample virtually every region of the electromagnetic spectrum, with spatial resolutions from 0.5 to 5,000 m. The scientific community’s interest in spatiotemporal studies of global change, environmental monitoring, and human impacts involves the use of remote sensing data. Remote sensing systems, particularly those located on satellites, provide a repetitive and synoptic vision of Earth, which is of great interest in monitoring and analyzing human activities and their impacts. The activities include the evaluation and monitoring of the environment like urban growth and hazardous waste; detection and monitoring of global changes, deforestation, global warming, and exploration of non-renewable resources and their land use; civil engineering;, the acquisition of satellite imagery from relevant sources; the preprocessing of satellite imagery as per requirement; and the development and classification of satellite data using fuzzy C-means (FCM), modified FCM, K-means, and fuzzy inference system (FIS) techniques.

Keywords: FCM, modified FCM, K-means, FIS techniques

1.1 Introduction

In this chapter, an introduction to remote sensing theory, the differences between practical and ideal remote sensing systems and the Landsat 8 data characteristics and concepts of electromagnetic radiation are presented [1, 2]. Remote sensing can be broadly defined as the science of obtaining useful information about physical objects and/or the environment through recording and measuring energy patterns from the sensor systems. The information about distant objects and the environment is obtained through the electromagnetic radiations emitted or reflected by the Earth’s surface features, which are of interest. Multiple data users that make use of the ideal remote sensing system would be able to acquire the required data at a higher speed with less or no expense of any required area of interest [3, 4]. Given this information, multiple data users would be able to make decisions on managing and observing the Earth’s surface features. A real remote sensing system encounters a lot of problems in each stage of the remote sensing system. The following section explains the limitations of all ideal remote sensing systems. The spectral distribution of reflected and/or emitted electromagnetic energy is not uniform, and it varies from time and place on different Earth features. Passive remote sensing systems entirely depend on the energy from the sun. Solar energy is non-uniform with respect to time and place. The sources used in the remote sensing systems are also non- uniform with respect to wavelength and time. Therefore, there is always a need to calibrate these sources depending on the mission, time, and location. In a real remote sensing system, there is always a need for atmospheric and radiometric corrections due to atmospheric errors. The atmosphere always modifies the energy emitted and reflected by the Earth’s surface features. Eliminating the atmospheric effects is important in those applications involving observations of the same geographical area. Different materials do not reflect and emit energy uniquely. There is spectral overlapping in the recorded data. The spectral response plays an important role in detecting, identifying, and analyzing the Earth’s surface materials. A good understanding of energy interactions is required to obtain information about the required features. From the above points, it is clear that super sensors do not exist. The sensors cannot be sensitive to all possible wavelengths and have limits with respect to sensitivity. The sensors record the objects according to their spatial resolution. The ability of the sensors to differentiate the smallest object and separate it from its surroundings is called spatial resolution. The spatial resolution depends on the heterogeneity of the ground area being sensed. The digital images obtained consist of mixed pixels causing problems in identifying the land cover classes. Depending on the application, the choice of sensors varies from airborne vehicles to space stations. Photographic systems produce images of higher spatial resolution, but spectral sensitivity is absent in those sensors. Therefore, to obtain information on all the land cover classes, sensors with higher spectral resolution are required rather than sensors with higher spatial resolution. However, sensors having higher spectral resolution are expensive. Proper image processing techniques are required to visualize if the sensor data are of low resolution. Therefore, there are always tradeoffs between cost and resolution. Remote sensing systems generally are of two types: passive and active. An active remote sensing system possesses an illumination system or source of energy. It directs this energy to the objects to measure the energy. Some examples of active sensor systems are radars and laser scanners. The passive remote sensing system utilizes the sun’s energy to record the emitted and/or reflected values of the surface features. Landsat series sensors are an example for passive remote sensing systems. The sensors that generate artificial radiation to the Earth’s surface features are called active sensors. Radio detection and ranging or radar is used to detect the Earth’s surface features using the pulses of electromagnetic radiation in microwave ranges. These radiations are not affected by weather conditions such as clouds, fog, and wind. The reflected signal intensity is used to extract the information. These types of sensors using self-generated radiation are useful for specific satellite missions and operations [5, 6].

Sensors that use natural light and the thermal radiation of the Earth’s features to extract the information are called passive. This information is greatly affected by the seasons, time of capture, and height of the satellite. The Landsat satellite is equipped with spectrometers that measure the signals at a spectrum of bands. Therefore, multispectral channels are obtained, which provide greater information. Satellite imagery consisting of pixel values are the measures of the intensity of the electromagnetic radiation of the Earth’s surface features. The values of brightness differ in the image based on time, type of area, and sensors. Certain properties of imagery like resolution should be known. The individual elements of the digital image are called pixels. The size of the pixel and the type of sensor determine the spatial resolution. The length of the edges of the pixels is used to measure resolution. The number of spectral channels is defined as the spectral resolution of the image. The reflection of Earth surface features occurs in different wavelengths. The human eyes can recognize only the visible spectrum of radiations. The land area, which has high reflections in particular wavelengths, is sensed by the satellite sensors. Most of the Earth observation satellites have between three and eight bands. The linear imaging self-scanning sensor III (LISS-III) has four spectral bands. The higher spectral resolution allows larger features to be extracted.

The time interval the satellite takes to reach the same area is called temporal resolution. The temporal resolution is determined by the orbit of the satellite, the altitude, and the sensor’s characteristics. Generally, Earth observation satellites have a repetition rate of 14–16 days. Landsat 7 has 16 days. The highest temporal resolution is for meteorological satellites, which is 15 minutes [7, 8].

The surface reflectance characteristics of three main Earth surface features are discussed here:

• Vegetation: The chlorophyll pigment in leaves absorbs radiation in red and blue wavelengths but reflects in the green wavelength. The reflectance characteristics vary with wavelength [9, 10, 16, 18].
• Water: The water absorbs most of the radiation in the longer wavelengths. The water reflects in shorter wavelengths and hence blue in appearance. In the near-infrared wavelengths, the water is darker in color. The reflectance varies due to the depth of the water, the materials in the water, and the type of water [12].
• Soil: The nature of the soil determines the reflection and emission. The presence of moisture decreases the reflectance. The reflectance of soil is present in a large range of wavelengths depending upon the soil [13].

1.1.1 Overview on Landsat 8

Landsat 8 is an American Earth observation satellite launched in 2013. It is the seventh satellite to reach orbit successfully. The operational land imager (OLI) sensor consists of nine capturing devices, and thermal infrared sensor (TIS) has two capturing devices. The thermal bands measure the surface temperature and lighter pixels represent hot temperatures. Thermal bands provide a lot of information regarding heat units present in urban regions. The Landsat 8 orbit height is 705 km above the Earth’s surface. It collects 400 scenes of 185-km wide regions in one day, and an archive is made...