1. Remote Sensing Principles and Applications
The NASA Earth Science Division Operating Systems (as of February 2015)
NRSM532 System Ecology

2. Remote Sensing Definition
Acquisition of information about the condition and/or state of a target by a sensor that is not in direct physical contact with the target (Asrar, 1989)

3. Remote Sensing Methods
Reflected Solar Radiation
Active
(Radar, LIDAR)
Land Surface Emissions
(microwave)

4. Remote Sensing - origins
1948 – The first images of earth extending to the horizon inclusive of outer space

5. Remote Sensing - origins
1968 – Apollo 8, Earth rising over the moon.
First visions of the “Blue Marble”

6. Remote Sensing Provides
A synoptic view of a large area
Access to regions that are difficult to access or not accessible for in situ observations
Global coverage
Periodic monitoring
Data collection at wavelengths across the electromagnetic spectrum
Malaspina Glacier, Alaska
LANDSAT 7 image

7. The Electromagnetic Spectrum
Remote Sensing for Earth Observations

8. The Electromagnetic Spectrum

9. Concepts of Remote Sensing
Energy recorded by remote sensing systems undergoes fundamental interactions that should be understood to properly interpret the remotely sensed data.
The remotely sensed energy (EMR) originates from the Sun and…
is radiated by atomic particles from the Sun (source),
propagates through the vacuum of space at the speed of light
interacts with the Earth’s atmosphere
interacts with the Earth’s surface
interacts with the Earth’s atmosphere once again, and
finally reaches the remote sensor

10. Earth Surface Interaction
The incident energy will be either reflected, transmitted, or absorbed
The sum of the reflectance ( ρ ), absorption ( α ), and transmittance ( τ ), is equal to one in accordance with the law of conservation of energy. ρ + α + τ = 1

11. Atmospheric Effects on Radiation
The Atmosphere can refract, scatter, and absorb:
Refraction refers to the bending of radiation from its original path
Only a major factor in long path lengths through the atmosphere
Scattering refers to the redirection of radiation after interaction with a particle in the atmosphere
a function of the wavelength of the incident radiation and the size of a particle (e.g., gas molecule, dust, water vapor) encountered
Absorption is the incorporation of the radiation within the particle to alter the energy state of the particle
Gaseous absorption and aerosol absorption
Gases that cause the largest impact to RS are CO2, H2O, and O3
Wavelengths (<300 nm) are almost completely absorbed (e.g., O3)
CO2: greenhouse gas (infrared radiation absorption)
H2O: NIR, SWIR, far-infrared and microwave regions
Scattering and Absorption are referred to as attenuation or extinction

12. Atmospheric Transmittance
Transmittance: the fraction of incident EMR at a specified wavelength that passes through a sample (e.g. Earth’s atmosphere)
The amount of transmittance will determine what measurements of the surface can be made.
Spectral regions with poor transmittance are good for atmospheric sensing, not good for terrestrial remote sensing
Infrared Atmospheric window (8-12 µm) can penetrate the earth’s atmosphere

13. Solar & Terrestrial Radiation and Atmospheric Absorption
The spectral distribution of solar and terrestrial radiation
The absorption spectra of the major radiatively active gases and of the total atmosphere.
Chapin, Matson, Vitousek. Principles of Terrestrial Ecosystem Ecology, Springer 2011

14. Remote Sensing “Resolutions”
Four types: Temporal, Radiometric, Spatial, Spectral
Temporal resolution
Frequency of data collection (repeat cycle and revisit time)
How long the sensor remains over the target (integration time or shutter speed)
Mission lifetime or operation period
Radiometric resolution
Sampling changes in energy levels
Smallest detectable change in energy
Minimum and maximum detectable energy levels (Dynamic Range)
Spatial resolution
Spatial sampling of data points
Smallest area sampled (Pixel size, Ground Instantaneous Field of View-GIFOV)
Full area covered by the sensor (swath width)
Spectral resolution
Band spacing
Narrowest band width
Overall spectral coverage
Temporal

15. Temporal Resolution
How often a sensor can obtain data over a particular area of interest. Primarily a function of orbital characteristics, location of area of interest, and swath width … among others.
MODIS provides daily coverage of nearly entire Earth surface.
Polar orbiting satellite example of multiple overpasses in 1 day.
Landsat revisits an area every 16 days.

16. Radiometric Resolution
The radiometric resolution of an imaging system describes its ability to discriminate very slight differences in energy.
The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy.
Dependent on the number of divisions of bit depth in data collected by a sensor.
8-bit (28)
( )
16-bit (216)
(0 – 65,535)
2 bits, 22 = 4 possible values
8 bits, 28 = 256 possible values

17. Spatial Resolution
A measure of the smallest object that can be resolved by the sensor.
More commonly refers to the size of the pixel or the IFOV (instantaneous field of view)
Dependent on:
the distance from the sensor to target.
The wavelength and energy of reflectance/emission being measured.
Integration time (time spent over IFOV)

18. Spectral Resolution
Spectral resolution describes the specific wavelengths that the sensor can record within the electromagnetic spectrum.
Sensors are often categorized as Panchromatic, Multispectral, and Hyperspectral (Radar, Microwave, LIDAR)

19. Spectral Resolution
Sensors are often categorized as Panchromatic, Multispectral, and Hyperspectral
Measures across multiple bands allow for visual representations beyond what we normally see.

20. Radiometric vs. Spectral vs. Spatial Resolution
Temporal
Advances in one component require trade-offs in another.

21. Calibrations and Corrections
Types of calibration: Geometric and Radiometric
Geometric calibration: pixel location in latitude and longitude and height (orbital drift)
Radiometric calibration allows the sensor output to be converted to an absolute scale
VNIR/SWIR Atmospheric Correction
Sun angle is a critical factor in the VNIR/SWIR
Proper atmospheric correction in the VNIR/SWIR allows direct comparison of two scenes to determine changes in surface characteristics
Removes effects due to view and solar angles
Changes in atmospheric conditions are taken into account (aerosol amounts, water vapor content, etc.)

22. Satellite Orbits Geo-synchronous or Geo-stationary
satellites orbit at the same rate as the Earth rotation
Polar
Inclination angle is zero.
Allows global coverage
Sun-synchronous
Allow a satellite to pass over a section of the Earth at the same time of the day
Ascending node (pass)
travels northwards on one side of the Earth
Descending node (pass)
then south on the second half of its orbit

23. Types of Remote Sensors
Remote sensing instruments are of two primary types: Active and Passive Sensors
Passive sensors detect EMR that is emitted or reflected by the object or scene being observed. Reflected sunlight is the most common source of radiation measured by passive sensors
Active sensors provide their own source of energy to illuminate the objects they observe. An active sensor emits radiation in the direction of the target to be investigated. The sensor then measures the radiation that is reflected or backscattered from the target.
Carnegie Airborne Observatory AToMS Spectrometer
Passive case

24. Remote Sensing Platforms
A wide array of platforms are implemented, but are dominated by satellite and airborne systems.
Balloons
UAVs
Truck Mounted
GPS reflectometry
PhenoCams
Phenology Eyes Network

25. NASA Earth System Science Remote Sensors

26. NASA Earth System Science Remote Sensors

27. NASA Earth System Science Remote Sensors

28. NASA Earth System Science Remote Sensors

29. Data Terminology
Data Processing Levels for EOSDIS Data Products

30. Digital Image Processing Software
Commercial
Public Domain / Open Source
ENVI / IDL
ERDAS Imagine
Leica Photogrammetry Suite
- IDRISI
- ER Mapper
PCI Geomatica
eCognition
- GRASS
- MultiSpec (LARS Purdue)
DLGView
fGIS
OpenEV
NSIDC DataViewer
HDFView
Panoply
ncBrower

31. Data Formats HDF: The Hierarchical Data Format (HDF4 and HDF5)
netCDF: The network Common Data Format
ASCII: An American Standard Code for Information Interchange text file
Binary: Only computer readable format
TIFF: Tagged Image File Format. Raster format.
GeoTiff: TIFF having geographic data (.tfw file)
JPEG: File formatted using JPEG are not geolocated
Dealing with the wide array of data formats can be overwhelming – don’t let it keep you from applying these valuable data sources to your research!

32. MODIS Moderate Resolution Imaging Spectroradiometer
Platform: EOS Terra and Aqua
Pixel resolution: 250, 500, and 1000 m
Overpass times: 10:30 (Terra) and 13:30 (Aqua)
Spectral bands: 36
Started: 2000
Swath Coverage 2330km

33. MODIS
MODIS Bands

34. MODIS Products MOD01 Level-1A Radiance Counts
MOD02 Level-1B Calibrated Relocated Radiances
MOD03 Geolocation Data Set
MOD04 Aerosol Product
MOD05 Total Precipitable Water
MOD06 Cloud Product
MOD07 Atmospheric Profiles
MOD08 Gridded Atmospheric Product (Level 3)
MOD09 Atmospherically-corrected Surface Reflectance
MOD Snow Cover
MOD11 Land Surface Temperature & Emissivity
MOD12 Land Cover/Land Cover Change
MOD13 Vegetation Indices
MOD14 Thermal Anomalies, Fires & Biomass Burning
MOD15 Leaf Area Index & FPAR
MOD16 Surface Resistance & Evapotranspiration
MOD17 Gross & Net Primary Productivity
MOD18 Normalized Water-leaving Radiance
MOD19 Pigment Concentration
MOD20 Chlorophyll Fluorescence
MOD21 Chlorophyll_a Pigment Concentration
MOD22 Photosynthetically Active Radiation (PAR)
MOD23 Suspended-Solids Conc. Ocean Water
MOD24 Organic Matter Concentration
MOD25 Coccolith Concentration
MOD26 Ocean Water Attenuation Coefficient
MOD27 Ocean Primary Productivity
MOD28 Sea Surface Temperature
MOD29 Sea Ice Cover
MOD Temperature and Moisture Profiles
MOD32 Processing Framework
MOD Gridded Snow Cover
MOD Gridded Vegetation Indices
MOD35 Cloud Mask
MOD36 Total Absorption Coefficient
MOD37 Ocean Aerosol Properties
MOD39 Clear Water Epsilon
MOD43 Albedo 16-day L3
MOD44 Percent Tree Cover and Land Cover Change

35. Accessing MODIS Data Products
Download user-specified, geo-referenced, and geographically subset images in GIS-compatible format.

36. LANDSAT
Landsat satellites provide the longest imagery data record from visible, NIR, SWIR and TIR bands over four decades with fine spatial resolution.
The entire archive of LANDSAT data is now available for free via the USGS WELD system.

37. DAACs (Distributed Active Archive Centers)

38. Remote Sensing Web References
•Federation of American Scientists
•CRISP
•"Fundamentals of Remote Sensing Tutorial Notes:"
•NOAA Center for Satellite Applications and Research
•NASA Earth Observatory
NASA