ERT 245:GEOMATIC ENGINEERING REMOTE SENSING: ENERGY SOURCES

1. ERT 245:GEOMATIC ENGINEERINGREMOTE SENSING:ENERGY SOURCES GROUP A1: ANG KIEN HAU YONG EAN MONG RENUGA A/P BALAKRISHNAN NURUL HANI BINTI MD ZUBIR NUR HIDAYU BT MOHD JAMIL SITI NADHIRAH BT ABDULLAH

2. 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 • In much of remote sensing, the process involves an interaction between incident radiation and the target of interest.

4. WHY WE NEED REMOTE SENSING???

5. The work of geologists would be much easier if Earth were transparent and they could simply look down into the ground as they would into the sky. • But the ground is not transparent and for that matter, it is the sky, to which meteorologists look for information regarding atmospheric and weather patterns. • Some places are hard to see, and many are difficult or even impossible to visit physically.

6. Some places, such as the Sun or the Earth's core, could not be approached physically even by unmanned technology. • Hence the need for remote sensing, or the gathering of data without actual contact with the materials or objects being studied. • Some earth scientists define the term more narrowly, restricting "remote sensing" to the use of techniques involving radiation on the electromagnetic spectrum.

7. The latter category includes visible, infrared, and ultraviolet light as well as lower-frequency signals in the microwave range of the spectrum. • This definition excludes the study of force fields involving gravitational or electromagnetic force. • Remote sensing is used for a variety of measuring and mapping applications.

8. Applications of remote sensing go far beyond cartography (map making) and measurement. • Remote sensing makes it possible for earth scientists to collect data from places they could not possibly go. • In addition, it allows for data collection in places where a human being would be "unable to see the forest for the trees"—which in places such as the Amazon valley is quite literally the case.

9. HOW DOES REMOTE SENSING WORK???

10. Each eye sends a signal to a processor (your brain) which records the data and interprets this into information. Several of the human senses gather their awareness of the external world almost entirely by perceiving a variety of signals, either emitted or reflected, actively or passively, from objects that transmit this information in waves or pulses. Thus, one hears disturbances in the atmosphere carried as sound waves, experiences sensations such as heat (either through direct contact or as radiant energy), reacts to chemical signals from food through taste and smell, is cognizant of certain material properties such as roughness through touch, and recognizes shapes, colours, and relative positions of exterior objects and classes of materials by means of seeing visible light issuing from them.

11. Remote Sensing • Without direct contact, some means of transferring information through space must be utilised. • What is it??

12. EMR Electro-Magnetic Radiation

13. Electro-Magnetic Radiation • EMR is a form of energy that reveals its presence by the observable effects it produces when it strikes the matter. • EMR is considered to span the spectrum of wavelengths from 10^(-10) mm to cosmic rays up to 10^(10) mm. • Remote Sensing Technology makes use of the wide range Electro-Magnetic Spectrum (EMS) from a very short wave "Gamma Ray" to a very long 'Radio Wave'.

14. Electromagnetic Spectrum

15. ENERGY SOURCES/ILLUMINATION • The first requirement for remote sensing is to have an energy source which illuminates or provides electromagnetic energy to the target of interest • The sun provides a very convenient source of energy for remote sensing. The sun’s energy is either reflected, as it is for visible wavelengths, or absorbed and then re-emitted, as it is for thermal infrared wavelengths.

16. Types of Remote Sensing • In respect to the type of Energy Resources: • Passive Remote Sensing • Active remote Sensing • In respect to Wavelength Regions: • Visible and Reflective Infrared Remote Sensing • Thermal Infrared Remote Sensing • Microwave Remote Sensing • Band Use Remote Sensing

17. PASSIVE REMOTE SENSING • Remote sensing system which measure energy that is naturally available • Can only be used to detect energy when the naturally occurring energy is available • For all reflected energy, this can only take place during the time when the sun is illuminating the earth

19. ACTIVE REMOTE SENSING • Provide their own energy source for illumination • The sensors emits radiation which is directed toward the target to be investigated • The radiation reflected from that target is detected and measured by sensor • Example: • Laser fluorosensor • Synthetic Aperture Radar (SAR)

20. Advantages • Able to obtain measurement anytime, regardless of the time of day or season • Can be used for examining wavelengths that are not sufficiently provided by the sun • Disadvantages • Require the generation of a fairly large amount of energy to adequately illuminate targets

21. VISABLE AND REFLECTIVE IR REMOTE SENSING

23. Energy source : object itself • Any object with normal temperature will emit electromagnetic radiation with a peak about 10 μm • The visible remote sensing devices operate in the visible, near infrared, middle infrared and short wave infrared portion of the electromagnetic spectrum. • It makes use of visible, near infrared and short-wave infrared sensors to form images of the earth's surface by detecting the solar radiation reflected from targets on the ground.

24.  Different materials reflect and absorb differently at different wavelengths. Thus, the targets can be differentiated by their spectral reflectance signatures in the remotely sensed images • These devices are sensitive to the wavelengths ranging from 300 nm to 3000 nm. • The longest visible wavelength is red and the shortest is violet. Common wavelengths of what we perceive as particular colors from the visible portion of the spectrum

25. The visible and reflective remote sensing region is split into a number of bands, each of which is useful in distinguishing land cove features.  The following is just a guide based on LISS 3/4 and LANDSAT Bands 1-4. • Band 1 (0.45-0.52 µm): coastal water mapping, soil/vegetation discrimination, forest classification, man-made feature identification. • Band 2 (0.52-0.60 µm): vegetation discrimination and health monitoring, man-made feature identification. • Band 3 (0.63-0.69 µm): plant species identification, man-made feature identification. • Band 4(0.76-0.90 µm): soil moisture monitoring, vegetation monitoring, water body discrimination

26. The curve (a) and (b) are intersect at about 3.0 μm, spectral reflectance is mainly observed, while in region more than 3.0 μm, thermal radiation is measured. The two curve (a) and (b) shows the black body spectral radiances of sun at temperature of 6000 ̊K and an object with temperature of 300 ̊K without atmospheric absorption

27. Example of visible and reflective IR remote sensing • Photographic.— • Cameras and film are used. Photography provides the best spatial resolution but less flexibility in spectral data collection and image enhancement. Spatial resolution is dependent on altitude, focal length of lenses, and the types of film used. • Spectral resolution is limited to visible and near infrared wavelengths.

28. Electronic Spectral Sensors.— • Detectors are used, usually scanners, that may have less spatial resolution than photographs but can gather spectral data over wide spectral ranges that enable a wide variety of imaging processing, mineral, and geologic identification. These remote sensing systems include satellites, such as Landsat, airborne sensors carried on aircraft, andspectrometers carried on the ground. This type of remote sensing has several categories, including multispectral, hyperspectral, and imaging spectroscopy.

29. Vidicon. – • A television-type system. Vidicon systems generally are inferior to other types both spatially and spectrally. They are used mostly on space probes because of operational constraints.

30. THERMAL INFRARED REMOTE SENSING

31. THERMAL INFRARED REMOTE SENSING • Electromagnetic waves with a wavelength range between 3.5 and 20 micrometers. • Most remote sensing applications make use of the 8 to 13 micrometer range. • The source of radiant energy used in thermal infrared remote sensing is the object itself, because any object with a normal temperature will emit electro-magnetic radiation with a peak at about 10 m .

32. Can provide important measurements of surface energy fluxes and temperatures, which are integral to understanding landscape processes and responses. • One example of this is the successful application of TIR remote sensing data to estimate evapotranspiration and soil moisture, where results from a number of studies suggest that satellite-based measurements from TIR remote sensing data can lead to more accurate regional-scale estimates of daily evapotranspiration.

33. Thermal infrared remote sensing focuses on far infrared and mid infrared

34. The main difference between thermal infrared and the infrared (color infrared - CIR) is thermal infrared emitted energy that is sensed digitally, whereas the near infrared "photographic infrared" is reflected energy that causes a chemical reaction in film emulsion.

35. Thermal remote sensing exploits the fact that everything above absolute zero (0 K or -273.15 °C or –459 °F) emits radiation in the infrared range of the electromagnetic spectrum. • How much energy is radiated, and at which wavelengths, depends on the emissivity of the surface and on its kinetic temperature • Emissivity is the emitting ability of a real material compared to that of a black body

36. Factors Affecting the Kinetic Temperature Can be categorised in two groups • Heat energy budget Heat energy budget includes factors such as solar heating, longwave upwelling and downwelling radiations, heat transfer at the earth-atmosphere interface and active thermal sources such as fires, volcanoes etc. b) Thermal properties of the materials Thermal properties of material include factors such as thermal conductivity, specific heat, density, heat capacity, thermal diffusivity and thermal inertia of the material.

37. APPLICATION • Thermal property of a material is representative of upper several centimeters of the surface. • It proves to be complementary to other remote sensing data and even unique in helping to identify surface materials and features such as rock types, soil moisture, geothermal anomalies etc. • The ability to record variations in infrared radiation has advantage in extending our observation of many types of phenomena in which minor temperature variations may be significant in understanding our environment. • Thermal infrared remote sensing reserves immense potential for various applications.

38. Limitations of thermal infrared remote sensing • It can be very expensive to acquire and process • Most thermal imaging systems have strict operational/technical parameters. - detector materials must be kept extremely cold during use • Thermal infrared imaging systems are notoriously difficult to calibrate - because temp differences can be very subtle and interactions with atmospheric moisture are unpredictable • The data collected is computationally expensive due to the iterative nature of filtering software • Thermal images can be difficult to interpret compared with other types of imagery, it takes some getting used too (false color helps) • Thermal images of water measures only the very top layer of the water surface - because those wavelengths are attenuated/absorbed very rapidly, especially in water

40. MICROWAVE REMOTE SENSING(RADAR)

41. Where Radar comes from….?? • Radar was originally developed in the 1950s, • 1st airborne system --> SLAR (Side-Looking Airborne Radar) • Later,SAR (synthetic Aperture Radar) was developed and widely used in many countries for civilian applications

42. What is the Radar (Microwave) Remote Sensing • RADAR stands for "RAdio Detection And Ranging“ ----> sending out pulses of microwave electromagnetic radiation • Known as "active sensor“ will measures the time between pulses and their reflected components to determine distance. • Wavelength of Radar in range between <1 mm to 1m

43. Advantages of Radar • It have long wavelength, allows the systems to "see" through clouds, smoke, and some vegetation. • it can be operated day or night  an active systems • Radar wave can penetrate clouds, haze, dust and so on but the heaviest of reflected depends on channel used.

44. Effect using Radar in imaging Color Aerial Photography Processed Radar Imagery

45. Continue… Radar Derived DEM (Digital Elevation Model) Color Photography

46. Disadvantages of Radar • Its the non-unique spectral properties of the returned radar signal. • Its only shows the difference in the surface roughness and geometry and moisture content of the ground (the complex dielectric constant).

47. Types of Imaging Radar SLAR (Side-Looking Airborne Radar) SAR (Synthetic Aperture Radar) • develop by guess who in the 1950's • airborne, fixed antenna width, sends one pulse at a time and measures what gets scattered back • resolution determined by wavelength and antenna size (narrow antenna width = higher resolution) • developed by those responsible for SLAR, • this configuration not depend on the physical antenna size although to achieve higher resolution • the receiving antenna components and transmitter components need to be separated. • "synthesizes" a very broad antenna by sending multiple pulses

48. Imaging Radar Side-looking Airborne Radar (SLAR) Synthetic Aperture Radar

49. Radar Resolution Radar resolution has two components "range" resolution "azimuth" resolution

50. Radar Resolution "Range" resolution • As seen in this diagram, if the distance between the two houses labeled A and B were greater than {Pulse Length ÷ 2} then they would be discerned as two separate features. • Since, in this figure the slant range distance is less than {Pulse Length ÷ 2}, the reflected signals are "blurred.”