Introduction of Remote Sensing”Remote sensing is the science of acquiring information about the Earth’s surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.
“Firstly, to understand what Remote Sensing is, we need to know all components of Geo Information Technologies. GIT consists of three main components: (1) Remote sensing, (2) Geo Information Systems (GIS) and Navigation Systems or Global Positioning System (GPS).As I already mentioned, “Remote Sensing is a method to observe the earth surface or the atmosphere from out of space using satellites (space borne) or from the air using aircrafts (airborne).” Remote Sensing uses a part or several parts of the electromagnetic spectrum (EMS). For recording the EMS it is required to have a source of energy or radiation. And the best source for the Earth is the Sun.
As we know, during the daytime Earth becomes solar energy from the Sun. There is a total reflection of around 31% of the Sun energy by the atmosphere, clouds, and the earth surface and 69% of absorption by land and oceans, clouds and by molecules in the dust of the air. From this 31% of reflected energy around 9% is ground reflection, which is recorded from the satellites and space crafts.Nowadays there are cluster of different satellites around the Earth, which are orbiting around the Earth, recording, and gathering data of the target object regularly or even daily bases. These imaginaries of Remote Sensing have a wide usage in mapping land-use and cover, agriculture, soils mapping, archeological investigations, military observation, geomorphological surveying, land cover changes, deforestation, vegetation dynamics, water quality dynamics, urban growth and city planning.
For land cover changes, there is a very good example in green space disappearances in Mziuri Park, Tbilisi. Given Orto photos provides a valuable information for analyzing and assessing the situation.Orto photo 2005 (maps.reestri.gov.
ge) (1)Ortho photo 2010 (maps.reestri.gov.ge)Ortho photo 2014 (maps.reestri.gov.
ge)Google mas satellite photo 2018As you can see in the ortho photos the Mziuri park was getting smaller and smaller year by year. First there was built a highway, which took reasonable part of the green area, but even later slow by slow the green part is disappearing.Types of Remote SensingAnother type of Remote Sensing is earth collecting information, which is possible in an passive or active way. A passive Remote Sensing system is measuring energy that is naturally available. God example of passive Remote Sensing are our eyes.
Every day we are sensing our environment remotely without touching them, but our eyes are not able to measure the electromagnetic spectrum (EMS). Human eyes capture only the visible part and use only a small part of EMS (only at daytime, when the sun in illuminating the Earth). Though, in the nature there are some animals and birds, which are more sensitive with other part of EMS, for example: bees and butterflies can see an ultraviolet spectrum, which helps them to navigate into a flower’s sweet spot.
For human eyes this invisible part of EMS as infrared or thermal infrared light cannot be assessed by our visual system, which means, by observing an object through the distance we cannot assess the temperature, humidity or composite minerals.On the other hand, the counterpart to Passive Remote Sensing is Active Remote Sensing, which contains their own energy source for illumination. For example: We cannot see in the darkness, but if we provide our own source of light by caring a flashlight and shining toward the target object, we are able to measure the EMS, which was invisible so far. In this case we perform an Active Remote Sensing by supplying our own source of energy for illuminating the object.Elements of Remote SensingThe processing of Remote Sensing involves an interaction between incident radiation and the target of interest, which is exemplified by the use of imaging and mapping systems. The following elements are taking part in the process:A. Energy source/illumination – The Sun, which is providing electromagnetic energy to the target of interest or an active source like a flashlight.B.
Radiation and the atmosphere – The interaction between the Sun and the Earth.C. Interaction with the target – The image which will be made by interpretation and analysis.
D. Recording of energy by sensors – After scattering the energy from the target, the sensors record this EMR. Different objects have different reflection. If the energy is reflected from the water it will have different reflection.E. Transmission, reception, and processing.F. Interpretation and analysisG.
Application – This is the most important part as the collected information are applied for better understanding a problem. There are developed various applications from surveying, optimizing to city planning.Advantages and disadvantages of Remote SensingRemote Sensing has a wide usage in a different natural planning or researching sciences and its importance and advantages are clear. The technology provides a punctual view for analyzing the processes and providing repetitive look at the same area. Remote Sensing can help to see a broader portion of the spectrum than the human eye and some remote sensors operate in all seasons, at night and in bad weather conditions.Besides all the advantages of this technology, Remote Sensing still has the following weaknesses. First of all it is about money as it is reasonably expensive to build and operate Remote Sensing systems. Secondly measurement uncertainty can be large, needs ground verification and does not provide enough details.
Furthermore it is maybe not the proper tool for small areas and satellites data interpretation can be difficult – need to understand theoretically how the instrument is making the measurements. And last but not least, you need to have some knowledge of sampling phenomena.Besides all mentioned disadvantages, the main problem of satellite observation is space pollution around the Earth, called debris or space junk. As long as an object is above the last traces of Earth’s atmosphere, it will stay in orbit for thousands or even millions of years. According to NASA’s researches more than 500,000 pieces of debris aretracked as they orbit the Earth. They all travel at speeds up to 17,500 mph, fast enough for a relatively small piece of orbital debris to damage a satellite or a spacecraft.Using remote sensing for urban planningMost of the work connected to Remote Sensing has been focused on environmental issues, but its usage in urban planning aspects is becoming very popular, useful, and necessary.
Urbanization is not a modern process, but the transformation of cities is rapid. There are many changes going on about the social and living atmosphere at a global scale. In some urban areas density and city building is growing so fast, that quick response and accurate physical planning of the cities and towns are so urgent, that otherwise uncontrolled urbanization would create many problems. Problems like in our capital Tbilisi where urban planning is not well-advanced and Remote Sensing is not in use like it should be. In Tbilisi we experience nowadays an uncontrolled, unplugged and incorrectly locating of buildings. This is mainly caused by the interests of investors who have profit in their mind. This short-term thinking results in disappearance of green spaces and public areas.
We face huge problems regarding noise and air pollution, disposal of waste. Furthermore, citizens have difficulties in traveling through the city as there is a lack of good public transport, everybody has to rely on private cars which causes traffic congestion.As the Remote Sensing is a technology about observing and measuring objects from a distance, it is valuable and fundamental tool for city planners and territorial management policy makers. Right now there are actual researches going on in Tbilisi about brownfield areas. Satellite photographs are actively used for analyzing and visualizing real picture of the target area in Tbilisi to raise awareness of their importance.Brownfields are the huge closed areas in Tbilisi, which was former fabrics and railway station in Soviet Union. These areas are scattered throughout Tbilisi and a huge part is located also in the city center (Station square area, Picture 2).
The whole Brownfields area is around 450 Ha. The biggest part is located in south of Tbilisi, which can be planned as a new future urban area.Brownfields in Tbilisi (1)Brownfield – station square area (2)A great initiative is founded by the so called Real Laboratory group, which is a community of students, professors and businesses, who want to increase districts in Tbilisi. The current new project is about sustainable planning and renovation of the district “Plekhanovi”.
New concepts and territorial management plans are created based on city architecture and city maps. Maps are combined with aero and satellite pictures in order to perceive the area as a whole. This big picture view then helps to recognize patterns and plan improvements.(3) (4)ConclusionAs a summary, remote sensing imagery has many applications in cartography, land use, agriculture, oils mapping, forestry, city planning, grassland management and even in archaeology. In order to use such imagery, one must have considerable knowledge about the Earth’s surface and a strong background in technology to acquire remote sensing data and find techniques to analysis these data sets. Since the Earth’s surface consists of a mosaic of environmental conditions, geographers need to combine their knowledge in both the geo science and social science to discover innovative solutions based on remote sensing.