Chapter 1 Flashcards
λ wavelength f/v frequency μm micrometer 10^-6 nm 10^-9 Ang 10^-10 
- Define Remote Sensing
Collection of information about an object or system without coming into direct physical contact with it. That information is nearly always carried by electromagnetic radiation (EMR).
What sort of measurements in Remote Sensing (laundry list)
Measuring force fields, EMR, or acoustic energy employing cameras, radiometers and scanners, lasers, radio frequency receivers, radar systems, sonar, thermal devices, seismographs, magnetometers, gravimeters, scintillometers, and other instruments
Seven reasons we do remote sensing?
Unobtrusive.
Automated.
Useful for extreme conditions.
Combination of spatial and temporal coverage.
Extends our senses (beyond visible light)
Near real-time
No political boundary?
Spatial coverage
Global, regional, local
Seven Applications of remote sensing
- Meteorology
- Oceanography
- Glaciology Sea Ice Research
- Geology
- Agriculture
- Hydrology
- Disaster control
Meteorlogy uses of remote sensing
– Profiling atmospheric temperatures and water vapor
– Measuring wind speed
– Watching evolution and trajectories of storms
Oceanography uses of remote sensing
– Measuring sea surface temperatures and salinity – Mapping of ocean currents
– Measuring sea level rise and variability
Glaciology uses of remote sensing
– Mapping motion of glaciers and ice sheets
– Monitoring ice melt
– Determining navigability of polar oceans
Geology uses of remote sensing
– Identification of rock types
– Location of geological faults and anomalies
Agriculture uses of remote sensing
– Monitoring extent and type of vegetation
– Mapping soil types
– Estimating vegetation biomass
Hydrology uses of remote sensing
– Assessing water resources
– Forecasting melt water runoff from snow
– Determining soil moisture
Diaster control uses of remote sensing
– Warnings of sand and dust storms
– Flooding
– Monitoring of pollution
Analog benefits (4)
– Medium is film Benefits • Easy to view • High spatial resolution • Sometimes cost-effective • Compact
Analog drawbacks (4)
– Medium is film
Drawbacks
• Difficult to transmit remotely
• Difficult to edit after acquisition
• Limited response to light (visible and near infrared wavelengths only)
• Degradation over time can limit archive capabilities
Digital benefits (4)
• Wide variety of detectors
– Electromagnetic and other types
– Large amplitude range
• Data easily transmitted remotely
• Data easily edited/manipulated/enhanced after acquisition
• Long-term archiveDigital drawbacks (3)
- Storage requirements can be large
- Reduced spatial resolution in many cases
- Requires sophisticated equipment and analysis techniques to use
Four types of Remote Sensing Systems
- Active Sensor – illuminates subject from an artificial (on- board) energy source
- Passive sensor – uses naturally emitted radiation from the sun or the object being observed
- Imaging sensor – creates a “picture” by scanning across a linear array of detectors while the array moves through space
- Non-imaging sensors – measures along a transect or at a point
5 characters for Summarizing Remote Sensing Systems
- Platform:Ground,airborne,satellite
- Media: digital or analog
- Illumination: passive or active
- Detector configuration: imaging, single-point, transect or sounding
- Spectralrange:visible,infrared,microwave,etc.
Conduction
transfer of kinetic energy between atoms or
molecules
Convection
transfer of kinetic energy by physically moving mass that contains that energy
Radiation
propagation via waves or particles through a vacuum or medium
Sources of EMR (active and passive)
– Sun and Earth are both passive sources of EM radiation
– Lasers and radars are active sources of EM radiation
How is EMR generated?
– Kinetic: motion of atoms or molecules producing heat (thermal)
– Electrical: generation of electric fields radio frequency
– Magnetic: polarization of charged atoms (microwave)
– Chemical: molecular excitation (visible)
Electromagnetic waves (basic definition)
Energy travels in waves described by
– Wavelength λ ( of frequency f/v), crest to crest
– Amplitude (a), crest to midline
Visible wavelength range
λ = 390 nm – 750 nm (3.9 - 7.5 x10^-7 m)
Blue:.4-.5 μm
Green: .5-.6 μm
Red: .6 - .7 μm
Most common remote sensing data types (EMR)
visible, infrared, thermal, and microwave
• Sun (most impt)
– Reflected solar energy 0.3 – 2.5 (3) μm
• Earth
– > 6 μm for self-emitted energy
μm = 1x 10^-6 m
Applications for Remote sensing (Summary)
• Remotely gathering information carried by EMR
• Quantitative analysis of digital information
– Image interpretation from hard copy is history
– Additional computational and analytical skills are required
• Global change issues can be addressed
• Highly interdisciplinary
Microwave wavelength range
λ = 1 mm – 1 m ( 1 x 10^-7 to 1 x 10^-9 nm))
Infrared wavelength range
λ = .75 - 30 μm (1,000 nm – 30,000 nm)
near IR = .75 to 1.3 μm
mid (short-wave) = 1.3 - 3 μm
thermal IR = two bands 3 - 5 μm and 8-14 μm
far IR = 3 - 30 μm
Collateral data
Aka ancillary data
Digital elevation models (DEMs), maps, political boundary files, population stats, etc. often in GIS
Formula for relationship between wavelength and freq
c = λv
3.0 x 10^8 m/s = λ (in μm or nm) x v (in Hz, or 1/s)
Add spectral ranges
tba
