INTRODUCTION REMOTE SENSING

1. Prepared by: SameraSamsuddinSah Biosystems Engineering Programme School of Bioprocess Engineering Universiti Malaysia Perlis (UniMAP) INTRODUCTION REMOTE SENSING

2. DEFINITION

3. Remote Sensing Process Components Energy Source or Illumination (A) Radiation and the Atmosphere (B) Interaction with the Target (C) Recording of Energy by the Sensor (D) Transmission, Reception, and Processing (E) Interpretation and Analysis (F) Application (G) Source: Canadian Centre for Remote Sensing

4. FIELD OF APPLICATION

5. SATELLITE Man-made object launched into space to orbit the Earth, moon, sun or other celestial body. Platforms launched for remote sensing, communication, and telemetry (location and navigation) purposes. • Satellite communication : • Ground segment • Space segment Moon is a natural satellite

6. Satellite : Power sources • Solar cells • Nickel Cadmium battery Technology has not progressed sufficiently for nuclear power sources to be used as a power source.

7. Satellite : Orbits & Swaths

9. SENSOR

10. Types 0f Sensor • Have 2 types of sensor, • Passive Sensor and • Active Sensor

11. Passive Sensor: • Passive sensors detect electromagnetic radiation emitted from an object.  • Record incoming radiation that has been scattered, absorbed and transmitted from the Earth in transit from its original source, the Sun.

12. Electromagnetic Radiation • Day – reflected any emitted • Night- emitted • Contrast with other geophysical techniques

13. Electromagnetic Spectrum

14. Some are sensor are designed to receive all ‘green’ wavelengths, other that more targeted toward infrared wavelengths. • In infrared viewer, is specially made to ‘see’ objects emitting infrared radiation (even in the dark). • In general terms, sensor that use external energy sources to “observe” an object are called “Passive Sensor”. • Sun is main sources.

15. Types of Passive Sensor: • Have 5 types of Passive Sensor, they are:- 1) Gamma-ray spectrometer • Passive sensor that detects gamma rays. • The sources for the radiation is are generally upper-soil layers as well as rock layers.  • Caused by radioactive decay.  •  Used to explore mineral deposits.

16. Passive Sensor: 2) Aerial cameras • Used in aerial photography. • Aircraft serve as a platform as well as many low-earth orbiting satellites deploy many aerial cameras. • Used for topographic mapping.

17. Passive Sensor: 3) Thermal infrared video cameras • Equipped to detect radiation in the near-infrared range. • Sometimes combined with active sensors, such as radar, to provide additional information. • Aircraft as well as satellites can serve as platforms.

18. Passive Sensor: 4) Multispectral scanner  • Records information in the visible and infrared spectrum. • Scans the Earth's surface for various wavelength bands. • Satellites act as platforms for such passive sensors. • Used for geological purposes.

19. Passive Sensor: 5) Imaging Spectrometer • Similar to the multispectral scanner. • Scans very narrow wavelength bands of the spectrum. • Satellites are used as platforms. • Used for determining the mineral composition of the Earth's surface and concentrations of suspended matter in surface water.

20. Passive sensor • Disadvantage – if the sky is covered with clouds, they cannot be used to observe the Earth surface (or oceans)

21. Active sensor: • Sensor that able to direct energy at an object in the form of electromagnetic radiation (EMR).  • Object is scanned and the sensors detect any radiation reflected back from the object. • Types of active remote sensing: • Active Optical Remote Sensing • Active Thermal Remote Sensing • Active Microwave Remote Sensing

22. Active Optical Remote Sensing • Active optical remote sensing involves using a laser beam upon a remote target to illuminate it, analyzing the reflected or backscattered radiation in order to acquire certain properties about the target. • The velocity, location, temperature and material composition of a distant target can be determined using this method. • Example: • LIDAR( Light Detection and Ranging)

23. Active Thermal Remote Sensing • Thermal remote sensing deals with information acquired primarily in the thermal infrared range.  • The majority of the thermal remote sensing is done using passive sensors.

24. Active Microwave Remote Sensing • Active microwave remote sensing uses sensors that operate in the microwave region of the electromagnetic spectrum. • Example: • RADAR (Radio detection and ranging)

25. Passive sensing relies on reflected sunlight and emission from hot objects (top). Active sensing illuminates the object with its own light source; a laser in this example (bottom).

26. PLATFORM • A satellite platform is the service module section of a satellite. • Or the vehicles or carriers for remote sensors • 3 types of platform: • Ground Based Platforms • Airborne Platforms • Space-borne Platforms

27. 1) Ground Based Platform: • Is the remote sensing platform that position the sensor at the Earth's surface • Used for close-range, high-accuracy applications, such as architectural restoration, crime and accident scene analysis, landslide and erosion mapping. • It is either static (tripod or mast) or dynamic (moving vehicle).

28. These systems are fixed to the Earth • The ground-based sensors are often used to record detailed information about the surface or measure environmental conditions such as air temperature, wind characteristics, water salinity, earthquake intensity and such. • Example: -DOE ARM (Atmospheric radiation Program) -NASA AERONET (Aerosol Robotic NETwork).

29. 2) Airborne platforms: • Are primarily stable wing aircraft, although helicopters are occasionally used. • Used to collect very detailed images and facilitate the collection of data. • Up to 50 km from earth. • Examples: • NCAR, NOAA, and NASA research aircrafts.

30. 3) Space-borne platforms: • Platforms that located about 100 km to 36000 km from earth. • Examples: -rockets, satellites, shuttle • Types of spaceborne platforms: -Space shuttle: 250-300 km -Space station: 300-400 km -Low-level satellites: 700-1500 km -High-level satellites: about 36000 km

31. AIRBORNE IMAGERY Aerial Camera Systems The recent introduction of digital cameras has revolutionized photography. Digital and film-based cameras both use optical lenses. Film-based cameras: use photographic film to record an image. Digital cameras: record image data with electronic sensors. Advantage of digital camera: can store, transmit and analyze the image data. Types of camera systems: small-format and large-format.

32. Small-format system • Consists one or more cameras • Using smaller photographic format (negative size-35mm) • Do not have high-quality lens to meet the normal measurement accuracies. • Very useful and inexpensive for updating land-use changes.

33. Large-format system • Consists only single camera. • Uses fixed focal length, large-format negative (230mm by 230mm). • Strictly used for aerial photography. • Equipped with a highly corrected lens and vacuum pressure to minimize distortion.

34. Flight Lines and Photograph Overlap • Factors need to consider: • Using suitable aircraft and technical staff. • The study area must be outlined carefully – using GPS to maintain flight line alignment. • Photographs must be taken under cloudless skies.

35. Figure 1: Flight line and photograph overlap

36. Figure 2: Photograph overlap along flight line

37. The number of air photos required to cover study area is very important. • For photographic scale of 1: 10,000 • 1 photograph cover 1 km2 • if area need to cover 500 km2 , the number of air photos is 500/1 = 500 nos . • But, if the scale decreased to 1:5000, the number of air photos is 500 x (10000/5000)2 = 2000 nos.

38. Ground Control for Mapping • Aerial photography is not perfect if it involves exposure to sudden and a flat surface. • Ground control points is the best way to overcome this problem. • To establish the control point; • Existing photography used for mapping. • Prior to the acquisition of the air photos.

39. Ground control is required for each data point positioning. • The accuracy depending on following requirements: • Measurements of distances and elevations • Preparation of topographic maps • Construction of controlled mosaics • Construction of ortho-photos and rectified photographs

40. Selection of ground control points for existing photograph based on following criteria: • Must be separated in the overlap area – model more stable and result more accurate. • Must be easily identifiable on both air photos – useless (if not) • Should be selected on the assumption that there are no changes since using the existing photographs. • Surveyor should consider ease of access to all points to minimize open-ended traverse lines.

41. For new photography, there are criteria need to follow; • The areas containing few identifiable ground control points. • Legal surveys of densely developed areas. • Municipal survey of roads and services

42. Mosaics • An assembly of two or more air photos to form one continuous picture of the terrain. • Extremely useful for the following application; • Plotting of ground control points at the optimum locations to ensure the required distribution and strength of figure. • A map substitute for field checkpoint locations and approximate locations of natural and cultural features. • A medium for presenting ground data.

43. Advantages: • Can be produced more rapidly. • Less expensive (cheaper). • Shows more terrain details. • Can interpreting subtle terrain characteristics ( tone, texture , and vegetation) • Disadvantages: • Horizontal scale measurements are limited due to relief displacement. • Not topographic maps (do not show elevations)

44. Aerial Surveying and Photogrammetric Mapping • Advantages using AS and PM over traditional ground surveying methods: • Low cost. • Reduced field work. • Faster in compilation (time saving). • Easy to record inaccessible terrain conditions. • Provide an accurate record of the terrain features. • Flexibility in term of scale. • More relevant (new technology)

45. Disadvantages: • Cannot get the real picture at dense vegetation area. • Cannot show the contour line • Need to do site visit - type of roads, surfacing etc

46. Aerial Photography Interpretation • Image interpretation is achieved by a combination of direct human analysis and by automated soft-copy processes. • Image interpretation techniques are based on 3 fundamental assumptions: • The remotely sensed image are records of the results of long- and short-term natural and human processes. • The surface features can be grouped together to form patterns that are characteristic of particular environmental conditions. • The environmental conditions and reflected image patterns are repeated within major climatic zones.

47. Applications of Air Photo Interpretation for Engineer and the Surveyor. • Can identify the land forms and site conditions (type of soil, soil depth, average topographic slopes, etc) • Can examine the topographic slopes, areas of unstable ground and density, and type of vegetation cover. • Air photo provide an excellent overview of the site and surrounding area. • Soil test holes should be used to verify the results of the air photo interpretation.

48. Elements of Image Interpretation • Shape: • Many natural and human-made features have unique shapes. • Often used are adjectives like linear, curvilinear, circular, elliptical, radial, square, rectangular, triangular, hexagonal, star, elongated, and amorphous.

49. Shape Jensen (2000)

50. Elements of Image Interpretation • Shadow: • Shadow reduction is of concern in remote sensing because shadows tend to obscure objects that might otherwise be detected. • However, the shadow cast by an object may be the only real clue to its identity. • Shadows can also provide information on the height of an object either qualitatively or quantitatively.