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• Remote - from afar/at certain distances
• Sensing - being aware of/detecting/acquiring info.
• Remote Sensing - acquiring info. at a distance
• 1840's - invention of camera more that 150 years ago (history of rs)
• Discuss the history of R.S.

  1840's - balloon as platform

  Followed by framed pigeons.

  First World War - camera mounted to an airplane.

  1950 -"remote sensing" coined by Ms. Evelyn L. Pruitt (U.S.)

  1960's to 1970's - primary platforms changed to satellite.
• Sensor - record the earth's surface in several bands what human eyes couldn't
• Remote Sensing - a practice of deriving information about the earth's land and water surfaces using images acquired from an overhead perspective, using electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the earth's surface. (James Campbell)
• How does remote sensing be similar and different from Surveying, Cartography and GIS?

  R.S. & Surveying

  Similar: provide fundamental biophysical information including x, y location and z elevation or depth.

  Different: R.S. can obtain data over very large geographical area.

  R.S., GIS, & Cartography

  R.S. gathering information without physical contact and those data can be use in GIS and Cartography. GIS and cartography cannot obtain fundamental information, they just rely on R.S. and etc. and can be used to show, display, or process that fundamental information.
• What is the difference between the active and passive remote sensing methods?

  Passive: Make use of naturally occurring available signal like thermal radiation from terrestrial object, sun, starlight or cosmic background radiation

  Active: Artificially produced wave which comes from the sensor itself.
• Wavelength is inversely proportional to Frequency.
• Passive system - detect naturally occurring radiation, radiation emitted by the sun and reflected by object (UV, VIs, NIR), thermal radiation emitted by all object not at absolute zero.
• Active System - emit radiation and analyze what is sent back to them use any type of EMR subject to restriction
• Differentiate active and passive sensors?

  Active: Emit their own energy to detect objects or has their own source of energy which is the sensor itself. Passive: Natural energy from the sun.
• Advantage of remote sensing?

  1. Provides repetitive looks at the same area.
  2. Remote Sensor "see" over a broader portion of the spectrum than the human eye.
  3. Data can be gathered from a large area, or a large volume of the atmosphere, in short period of time (snapshot)
  4. Airborne and Spaceborne systems can acquire data from locations that would be difficult (slow, expensive, dangerous, politically inconvenient)
  5. Most remote sensing systems generate calibrated digital data that can be fed into a computer for analysis
  6. Wide range of application
• Limitations of remote sensing?

  1. It is not panacea.
  2. Expensive to collect and interpret
  3. Instruments can become uncalibrated
  4. Active systems can be intrusive
  5. Human method - produced error
• Remote Sensing process: 7 elements

  1. Energy Source/Illumination
  2. Radiation and Atmosphere
  3. Interaction with the Target
  4. Recording of Energy by the Sensor
  5. Transmission, Reception, and Processing
  6. Interpretation and Analysis
  7. Application
• Energy source - first requirement in R.S.

  • illuminates or provides EM energy to the TOI
  • Common energy source: sun, sensor
• Radiation and the Atmosphere - the energy/radiation travels from its source to the target, once the energy makes its way to the atmosphere.

  • not all energy is emitted.
• Layer of atmosphere?

  Troposphere - 8 to 14.5 km

  Stratosphere - 50 km

  Mesosphere - 85 km

  Thermosphere - 600 km

  Ionosphere - 48 km above surface to about 965 km

  Exosphere - 10,000 km
• Troposphere - most dense, weather region
• Stratosphere - Ozone layer
• Mesosphere - coldest part of Earth's atmosphere
• Mesosphere - Meteors burns up
• Thermosphere - Aurora borealis & satellite
• Ionosphere - Layers of electrons and ionized atoms
• Ionosphere - overlapping in mesosphere and thermosphere.

  • radio communication
• Ionosphere - dynamic region that grows and shrink based on solar conditions.

  SUB REGIONS: D E F
• The ionosphere is an abundant layer of electrons and ionized atoms and molecules that stretches from about 48 kilometers above the surface to the edge of space at about 965 km.
• Interaction with the target - once the energy makes it way to the atmosphere it interacts with the target.

  • The interaction is dependent on the properties of both the target and radiation.
• Recording of Energy by the Sensor - after the energy has been scattered by or emitted from the target, we require a sensor (remote not in contact with the target) to collect and record the reflected emitted electromagnetic radiation.
• Passive sensing methods - make use of naturally available signals, such as thermal radiation of (a) terrestrial objects, (b) sunlight, (d) the cosmic background radiation
• Active methods - sense artificially produced waves after they interacted with the objects to be sensed.
• Transmission, Reception, and Processing - energy recorded by the sensor has to be transmitted often in electric form, to a receiving and processing station where the data are processed into an image.
• Interpretation and Analysis - processed image is interpreted, visually and/or digitally or electronically, to extract information about the target which was illuminated.
• Application - apply the information, we have been able to extract from the imagery about the target in order to better understand it, reveal some new information, or assist in solving a particular problem.
• Key requirements for remote sensing methods?

  An instrument on a given platform is needed that can detect and measure the information-carrying signal.

  A signal from the object to the observer must be propagated in an unambiguous way and without serious loss.

  An interaction must exist between the sensing wave and the object to be measured.

  The signal must be unambiguous to allow extraction of the correct information.
• Inversion - calibrated sensor signal
• Forward model - link between object & signal
• Dilemma in Remote Sensing?

  A transparent medium does not interact with the wave. But an interaction is needed with the object to be sensed.

  The problem is relaxed if the two media are clearly separated, for instance for sensing of surface properties.

  Remote Sensing needs a balance between interaction and transparency.
• Sensor

  It is device that is used to collect and record the energy/radiation after it is being emitted or reflected.