Credit: NASA – Methane sources detected by remote sensing
Remote sensing science is considered a new science of the 20th century, where it was introduced initially in response to a sharp demand for it during the 1st and 2nd World Wars. They were used initially for military purposes, including reconnaissance and detection of the movements of groups of soldiers and identification of the topography of the land in order to develop detailed military plans. The most known spying military program was the American CORONA program, which used to photograph sensitive areas around the world with an accuracy of 2 meters during the period from 1960 to 1972. The said program was uncovered only in 1995 when more than 800 thousand aerial photos were made available for civilian use to allow scientists, specialists and researchers in the various fields to study, analyse and use them
Credit: NASA – Giza Pyramids
The term “remote sensing” was used for the first time in 1960 when James Campbell defined it as the science of extracting information and data of the surface of land and water bodies using photos taken from above by recording electromagnetic rays reflected by or emanating from the land. A close clarifying example of the principle of remote sensing is the human eye, which uncovers a great deal of information about things and phenomena through looking and without any contact. This is similar to what happens in satellites where the interaction between the electromagnetic rays and the materials making the surface of the earth leads to reflection of certain degrees of this energy that varies based on the nature of each material. The information is stored as light bands on the electromagnetic spectrum tape (see photo No. (2)). It is found that chlorophyll chemistry has the ability to reflect a greater quantity of infrared rays compared to other types of rays and, as such, indicates the percentage of plant health or fatigue.
Credit: ESA – Illustrative image of the Centennial 2 satellite
The decade after 1960, added a lot to remote sensing sciences. Photography equipment and Global Navigation Satellite System(GNSS), are now carried on satellites instead of only on aircraft. This increased the ability to survey a greater part of the earth even outside the national boundaries of the state that owns the satellite as needed and within regular periods. This improved the quality of photos taken by satellites compared to photos taken by aircraft. Also, during this decade, and in light of the technological advancement in computer specifications, we moved from analogue to digital pictures. This heated the race between research centers, universities and space agencies for patents in the development of software and logarithms to help extract quality information to help understand and explain photos in a faster and more stable and accurate manner. This software was used to acquire information beyond the abilities of the eye to explain photos with the ability of sensors to get information outside the visible light; such as infrared and microwave rays on the wavelengths of the electromagnetic spectrum.
Credit: ESRI – The electromagnetic spectrum
Research and technological development were not restricted to analysing software. They also included the upgrading of photo-taking equipment carried on the satellites themselves. Active sensors that are self-dependent in producing the light required for photography using microwave spectrum packages that can penetrate clouds and dust (See photo No. (4)) were introduced. The first such active sensor was launched in 1978 under the name of SeaSat. It was provided with a detector that uses the SAR radar rays when the first satellites were using passive sensors that rely on sunrays for day photography (See photo No. (5)), as the case with our mobile cameras of today.
Credit: gisgeography – Passive Sensors
Credit: Gisgeography – Active Sensors
Remote sensing technologies garnered increased attention as a result of the observed expansion of usage of its application areas and technological and practical developments in an attempt to uncover the underground materials from outer space and help understand and list environmental problems and introduce useful solutions to guarantee the sustainability of the environment to satisfy the requirements of earth inhabitants. The various applications of remote sensing provided the information required to improve decisions in various fields in order to manage the ecosystem and the natural resources, economic and natural planning, and control pollution. This made remote sensing a technological tool that can contribute to decision making and control its execution. We list below examples of some of these applications:
- Monitoring green lands, estimating agricultural crops, identifying plant health, and detecting agricultural diseases, if any.
- Studying soil types and estimating their productivity and suitability for agricultural uses.
- Studying water bodies, directing their better utilization, and searching for ground water.
- Studying geological phenomena and desertification, contributing to oil and gas exploration operations.
- Managing disasters and crises using early detection devices to detect, for example, oil slicks and foresee their direction.
- Studying climatic changes at all levels of earth.
- Identifying archaeological areas and assisting in the detection of sites buried under sand or in fields.
Article written by: Eng. Ebrahim AlBurshaid