Essay Example on A review of the utility of remote sensing in agriculture

A review of the utility of remote sensing in agriculture 2400 Introduction Agriculture 240 The agricultural food supply is a product of a web linking soil water sunlight seed stock fertilizers technique human effort economy and planning Drury 1992 Agriculture is the main source of livelihood for many people to which globally there is a gross undersupply Its importance therefore requires effective management and decision making so resources are sufficiently used in the production processing and distribution of agricultural products Agricultural production systems can be highly vulnerable to variations in climate soil and topography of regions Kingra Majumder and Singh 2016 as well as other worldwide issues such as population increase leading to problems such as overgrazing which require a higher dependency and reliance on efficient crop growth All factors are intimately related with the biological technological and physical problems which face modern agriculture Lillesand et al 2008 and can affect its sustainable practice The monitoring and data collection of the agricultural production system is therefore essential for maximum efficiency and implementation of effective management decisions to maintain sustainable agricultural practices for the future Remote sensing can be used to monitor these issues as it forms a source for much of the information needed for implementing for efficient agricultural methods management of food resources and development of new agricultural areas Drury 1992 

Remote sensing definition and history 320 Lillesand and Kiefer 2000 define remote sensing as the science and art of obtaining information about an object area or phenomenon through the analysis of data acquired by a device that is not in contact with the object area or phenomenon under investigation The history of remote sensing spans back to the nineteenth century where before satellites were invented balloonists took photographs of the Earth s surface from a platform elevated above the earth The earliest known photograph was taken in 1859 of the village Petit Bicêtre near Paris Cracknell and Hayes 2002 In order to provide solutions to problems in different applications remote sensing offers ground based airborne and satellite approaches The requirements for remote sensing are large study areas features or processes changing rapidly limited or impossible ground access very high spatial heterogeneity and to see physical parameters not identifiable by human eye Ground based sampling is therefore is often insufficient to enable problems to be resolved as it is easier and quicker to look to solve these using digital image products produced by airborne camera systems and satellites Mathers 2003 Electromagnetic radiation Data is collected by sensors which are located on airborne or satellite remote sensing platforms The transport of information from an object or area being examined to these sensors are reflected or emitted by means of electromagnetic radiation transmitted through the atmosphere Rai n d The sensors measure the wavelengths of the electromagnetic radiation EMR reflected by targets on Earth based on the electromagnetic spectrum Different objects have different spectral signatures wavelengths which provide information on what is being observed Hyrien 2017 

The data collected requires analysis and interpretation to be converted from numerical arrays to information which can help address the initial problems Campbell 2002 The electromagnetic spectrum The electromagnetic spectrum is what the set of electromagnetic waves ranging from ultraviolet to microwave is called The visible spectrum makes up a small portion of the electromagnetic spectrum and the human eye cannot detect below and beyond the visible wave range Mather 2003 Remote sensing can acquire data in the visible as well as the invisible part of electromagnetic spectrum and the most useful wavelengths in remote sensing cover visible light and extends through the near and short wave infrared to thermal infrared and microwave bands Wójtowicz et al 2016 This is significant in using remote sensing for agricultural purposes as things which are invisible to the unaided eye such as detecting disease and infestations in crops or trees can be detected early and managed accordingly Characteristics of image remote sensors and instruments There are two different types of sensors on remote sensing platforms active and passive of which most remote sensing systems solely rely upon passive approaches Barrett and Curtis 1992 Active remote sensing detects signals that are artificially produced from specifically designed Radar systems Radio Direction and Ranging and passive remote sensors detect energy or force that emanates from the target itself at a natural source Resolution Sensors fixated on remote sensing platforms have their own resolutions and there are four different types spatial spectral radiometric and temporal Spatial resolution refers to the fineness of detail in a visible image where the higher the detail the higher the spatial resolution In digital remote sensing spatial resolution generally corresponds to ground pixel size 

There is a however a trade-off with an increase in spatial resolution as so does the necessity for more computer disk space resulting in greater disk storage and processing costs Verbyla 1995 Spectral resolution refers to the width across the electromagnetic spectrum that the remote sensing is detecting Verbyla 1995 Many vegetation types can be defined due to spectral differences due to the difference in colour so is significant in remote sensing in agriculture Radiometric resolution refers to the ability of a remote sensing system to record many levels of values Biophysical features of plants can be characterised spectrally by vegetation indices defined as unit less radiometric measures They are calculated as ratios or differences of two or more bands in the VIS NIR and SWIR wavelengths Wójtowicz et al 2016 Temporal resolution is the imaging revisit interval where a difference in the image is shown over time periods Temporal resolution generally increases at higher latitudes due to significant side lap between consecutive satellite passes Verbyla 1995 As remote sensing data acquisition platforms increase with height temporal resolution increases and spatial resolution decreases