SlideShare a Scribd company logo
1 of 16
1
PRESENTED BY,
Ch. Allaylay Devi
PhD. (Hort.) 1st Year
Dept. of FSc.
Introduction
• Remote sensing is the acquisition of information about an object or
phenomenon without making physical contact with the object and
thus in contrast to on-site observation.
• Remote sensing is used in numerous fields, including geography,
land surveying and most Earth Science disciplines (for example,
hydrology, ecology, oceanography, glaciology, geology)
• It also has military, intelligence, commercial, economic, planning,
and humanitarian applications.
2
Remote sensing
• “Remote sensing" generally refers to the use of satellite- or aircraft-based
sensor technologies to detect and classify objects on Earth, including on the
surface and in the atmosphere and oceans, based on propagated signals
(e.g. electromagnetic radiation).
• It may be split into active and passive remote sensing
• “Active" remote sensing (i.e., when a signal is emitted by a satellite or
aircraft and its reflection by the object is detected by the sensor).
• “Passive" remote sensing (i.e., when the reflection of sunlight is detected
by the sensor)
Techniques of remote sensing and its applications
• Conventional radar is mostly associated with aerial traffic control, early
warning, and certain large scale meteorological data.
• Doppler radar is used by local law enforcements’ monitoring of speed limits
and in enhanced meteorological collection such as wind speed and direction
within weather systems in addition to precipitation location and intensity.
• Other types of active collection includes plasmas in the ionosphere.
• Interferometric synthetic aperture radar is used to produce precise digital
elevation models of large scale terrain (RADARST, TerraSAR-X, Magellan).
• Laser and radar altimeters on satellites have provided a wide range of data. By
measuring the bulges of water caused by gravity, they map features on the
seafloor to a resolution of a mile or so.
• By measuring the height and wavelength of ocean waves, the altimeters
measure wind speeds and direction, and surface ocean currents and
directions.
• Ultrasound (acoustic) and radar tide gauges measure sea level, tides and
wave direction in coastal and offshore tide gauges.
• Light detection and ranging (LIDAR) is well known in examples of weapon
ranging, laser illuminated homing of projectiles.
It is used to detect and measure the concentration of various chemicals
in the atmosphere, while airborne LIDAR can be used to measure heights of
objects and features on the ground more accurately than with radar technology.
Vegetation remote sensing is a principal application of LIDAR.
• Radiometers and photometers are the most common instrument in use,
collecting reflected and emitted radiation in a wide range of frequencies.
The most common are visible and infrared sensors, followed by
microwave, gamma ray and rarely, ultraviolet.
They may also be used to detect the emission spectra of various
chemicals, providing data on chemical concentrations in the atmosphere.
• Stereographic pairs of aerial photographs have often been used to
make topographic maps by imagery and terrain analysts in trafficability and
highway departments for potential routes, in addition to modelling
terrestrial habitat features.
• Simultaneous multi-spectral platforms such as Landsat have been in use since
the 1970s.
• These thematic mappers take images in multiple wavelengths of electro-
magnetic radiation (multi-spectral) and are usually found on Earth observation
satellites, including (for example) the Landsat program or the IKONOS
satellite.
• Maps of land cover and land use from thematic mapping can be used to
prospect for minerals, detect or monitor land usage, detect invasive vegetation,
deforestation, and examine the health of indigenous plants and crops, including
entire farming regions or forests.
• Landsat images are used by regulatory agencies such as KYDOW to indicate
water quality parameters including Secchi depth, chlorophyll a density and total
phosphorus content. Weather satellites are used in meteorology and climatology.
• Hyperspectral imaging produces an image where each pixel has full
spectral information with imaging narrow spectral bands over a contiguous
spectral range.
Hyperspectral imagers are used in various applications including
mineralogy, biology, defence, and environmental measurements.
• Within the scope of the combat against desertification, remote sensing
allows to follow up and monitor risk areas in the long term, to determine
desertification factors, to support decision-makers in defining relevant
measures of environmental management, and to assess their impacts
Methods for monitoring indicators of vegetation condition
Spatial and temporal scales of monitoring
• It is a site-based monitoring programmes having a long a history of application
(e.g. Lawley et al., 2013 ; Sinclair, 2005), and still being commonly used today.
• It involves selecting sites from within homogenous patches of vegetation of the
same community type and site history.
• The majority of site-based assessments are quadrat-based where detailed
information is collected about the compositional, structural, and functional attributes
of a site.
• In some cases landscape metrics have also been added into overall measures, and
benchmarked scores are combined to give an overall condition index for individual
patches of sampled vegetation (Department, 2011; Michaels, 2006; Parkes et al.,
2003).
• It predominantly measure structural and compositional indicators of vegetation
condition, with less emphasis on indicators of function.
Assessed stress by utilising remote sensing
Detection of plant water stress using remote sensing
 These technologies acquire many hundreds of spectral bands across the spectrum
from 400 nm to 2 500 nm, using satellite, airborne or hand-held devices.
 The spectral characteristics of vegetation are governed primarily by scattering and
absorption characteristics of the leaf internal structure and biochemical constituents,
such as pigments, water, nitrogen, cellulose and lignin (Asner, 1998; Coops et al.,
2002). Pigments are the main determinants controlling the spectral responses of
leaves in the visible wavelengths (Gaussman, 1977).
 Chlorophyll pigment content, in particular, is directly associated with photosynthetic
capacity and productivity (Gaussman, 1977; Curran et al., 1992).
 Reduced concentrations of chlorophyll are indicative of plant stress (Curran et al.,
1992).
Spectral indicators of plant chlorophyll content
• In stressed vegetation, leaf chlorophyll content decreases, thereby changing
the proportion of light-absorbing pigments, leading to a reduction in the
overall absorption of light (Murtha, 1982; Zarco-Tejada et al., 2000).
• These changes affect the spectral reflectance signatures of plants through a
reduction in green reflection and an increase in red and blue reflections,
resulting in changes in the normal spectral reflectance patterns of plants
(Murtha, 1982; Zarco-Tejada et al., 2000).
• Thus, detecting changes from the normal (unstressed) spectral reflectance
patterns is the key to interpreting plant stress.
Spectral indicators of plant water content
• Plant water content at the leaf and canopy scales is often estimated using specific
spectral reflectance bands and spectral reflectance indices from near infrared,
middle infrared (MIR) and short-wave infrared (SWIR) regions of the
electromagnetic spectrum (Tucker, 1980; Hunt and Chun-Jiang et al., 2006).
• NIR and MIR spectral bands are highly correlated to water content of vegetation and
soils (Tucker, 1980; Hunt and Rock, 1989; Musick and Pelletier, 1986; 1988).
• Spectral bands from these regions have been used to delineate stressed trees from
non-stressed trees.
• In these regions of the electromagnetic spectrum, leaf water content has been
remotely assessed using bands 1 550 nm to 1 750 nm (Tucker, 1980)
• MIR reflectance increased with decreasing leaf water content.
Predawn leaf water potential
• Predawn leaf water potential measurements, often undertaken with a pressure
chamber, are useful for determining plant water stress.
• At predawn, xylem water potential has equilibrated with soil water potential after a
night of negligible transpiration.
• At this time, plant water potential is usually at its minimum for the day (Cleary and
Zaerr, 1984).
• The pressure chamber is most commonly used for estimating leaf water potential,
having the advantage of simplicity, reliability, instantaneous measurements, low
capital cost and portability (Scholander et al., 1965; Boyer, 1968; Ritchie and
Hinckley, 1975).
• It is commonly used as a plant water stress indicator and has also been used to
describe the water status of different species within a habitat
Leaf chlorophyll fluorescence
• Chlorophyll fluorescence measurements can be described using the typical
phases of a temporary fluorescence signal or transient.
• Therefore, this photosynthetic apparatus has been recognised as being a
good indicator of stress and stress adaptation of a plant and is associated
with the measurement of chlorophyll fluorescence (Salisbury and Ross,
1992; Strasser and Tsmilli-Michael, 2001; Strasser et al., 2001).
• Also, because changes in chlorophyll fluorescence may occur before any
physical signs of tissue or chlorophyll deterioration are manifested in the
plant, stress can be detected before the onset of physical damage
(Lichtenthaler et al., 2007).
Advantages and Disadvantages
Govender, et al., 2009
Conclusion
• With the launch and continuous availability of multi-spectral (visible, near-infrared)
sensors on polar orbiting earth observation satellites (Landsat, SPOT, IRS, etc.) remote
sensing (RS) data has become an important tool for yield modeling.
• Remote sensing research has identified several individual spectral bands and
vegetation spectral reflectance indices which have been used to detect plant water
stress.
• Depending upon the scale at which an investigation is being undertaken, it is
recommended that a practical approach to assessing plant water stress is adopted
through the use of at least one ground-based measurement.

More Related Content

What's hot

Application of gis and remote sensing in agriculture
Application of gis and remote sensing in agricultureApplication of gis and remote sensing in agriculture
Application of gis and remote sensing in agriculture
Rehana Qureshi
 

What's hot (20)

Geographical information system and its application in horticulture
Geographical information system and its application in horticultureGeographical information system and its application in horticulture
Geographical information system and its application in horticulture
 
Yield and Environmental Stresses
Yield and Environmental StressesYield and Environmental Stresses
Yield and Environmental Stresses
 
Geographic information system (GIS) and its application in precision farming
Geographic information system (GIS) and its application in precision farmingGeographic information system (GIS) and its application in precision farming
Geographic information system (GIS) and its application in precision farming
 
Geographical Information systems in Precision Agriculture
Geographical Information systems in Precision Agriculture Geographical Information systems in Precision Agriculture
Geographical Information systems in Precision Agriculture
 
PRECISION AGRICULTURE
PRECISION AGRICULTUREPRECISION AGRICULTURE
PRECISION AGRICULTURE
 
Doctoral credit seminar
Doctoral credit seminar Doctoral credit seminar
Doctoral credit seminar
 
Remote sensing application in agriculture & forestry_Dr Menon A R R (The Kera...
Remote sensing application in agriculture & forestry_Dr Menon A R R (The Kera...Remote sensing application in agriculture & forestry_Dr Menon A R R (The Kera...
Remote sensing application in agriculture & forestry_Dr Menon A R R (The Kera...
 
Remote Sensing and its Applications in Agriculture
Remote Sensing and its Applications in AgricultureRemote Sensing and its Applications in Agriculture
Remote Sensing and its Applications in Agriculture
 
Application of Remote Sensing in Agriculture
Application of Remote Sensing in AgricultureApplication of Remote Sensing in Agriculture
Application of Remote Sensing in Agriculture
 
Water use efficiency in plants
Water use efficiency in plantsWater use efficiency in plants
Water use efficiency in plants
 
Crop diversification for Sustainable Agriculture
Crop diversification for Sustainable AgricultureCrop diversification for Sustainable Agriculture
Crop diversification for Sustainable Agriculture
 
Precision agriculture
Precision agriculturePrecision agriculture
Precision agriculture
 
Crop modeling for stress situation
Crop modeling for stress situationCrop modeling for stress situation
Crop modeling for stress situation
 
Soil separability through remote sensing for land evaluation
Soil separability through remote sensing for land evaluationSoil separability through remote sensing for land evaluation
Soil separability through remote sensing for land evaluation
 
Application of gis and remote sensing in agriculture
Application of gis and remote sensing in agricultureApplication of gis and remote sensing in agriculture
Application of gis and remote sensing in agriculture
 
Land use cropping system
Land use cropping systemLand use cropping system
Land use cropping system
 
Climate change and its impact on Vegetable production
Climate change and its impact on Vegetable productionClimate change and its impact on Vegetable production
Climate change and its impact on Vegetable production
 
Climate change: Impact and its mitigation strategies in vegetable crops
Climate change: Impact and its mitigation strategies in vegetable cropsClimate change: Impact and its mitigation strategies in vegetable crops
Climate change: Impact and its mitigation strategies in vegetable crops
 
R 12013(crop weather modeling)
R 12013(crop weather modeling)R 12013(crop weather modeling)
R 12013(crop weather modeling)
 
Physiological limits in crop production
Physiological limits in crop productionPhysiological limits in crop production
Physiological limits in crop production
 

Similar to Assessing stress by using remote sensing

rsgis-unitii-160731062950.pdf
rsgis-unitii-160731062950.pdfrsgis-unitii-160731062950.pdf
rsgis-unitii-160731062950.pdf
BSuresh26
 
Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...
Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...
Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...
Hari Hariharasudhan
 

Similar to Assessing stress by using remote sensing (20)

Remote sensing in Plants
Remote sensing in PlantsRemote sensing in Plants
Remote sensing in Plants
 
Remote sensing application in monitoring and management of soil, water and ai...
Remote sensing application in monitoring and management of soil, water and ai...Remote sensing application in monitoring and management of soil, water and ai...
Remote sensing application in monitoring and management of soil, water and ai...
 
Surveying ii ajith sir class6
Surveying ii ajith sir class6Surveying ii ajith sir class6
Surveying ii ajith sir class6
 
Principles of remote sensing
Principles of remote sensingPrinciples of remote sensing
Principles of remote sensing
 
groundtruth collection for remotesensing support
groundtruth collection for remotesensing supportgroundtruth collection for remotesensing support
groundtruth collection for remotesensing support
 
Remote sensing in entomology
Remote sensing in entomologyRemote sensing in entomology
Remote sensing in entomology
 
Meteorological Satellites
Meteorological SatellitesMeteorological Satellites
Meteorological Satellites
 
Presentation of Introduction to basics of SONAR.pptx
Presentation of Introduction to basics of SONAR.pptxPresentation of Introduction to basics of SONAR.pptx
Presentation of Introduction to basics of SONAR.pptx
 
Introduction to Remote Sensing
Introduction to Remote SensingIntroduction to Remote Sensing
Introduction to Remote Sensing
 
rsgis-unitii-160731062950.pdf
rsgis-unitii-160731062950.pdfrsgis-unitii-160731062950.pdf
rsgis-unitii-160731062950.pdf
 
Remote sensing
Remote sensingRemote sensing
Remote sensing
 
Applications of remote sensing in geological aspects
Applications of remote sensing in geological aspectsApplications of remote sensing in geological aspects
Applications of remote sensing in geological aspects
 
applicationsofremotesensingingeologicalaspects-170606133459.pdf
applicationsofremotesensingingeologicalaspects-170606133459.pdfapplicationsofremotesensingingeologicalaspects-170606133459.pdf
applicationsofremotesensingingeologicalaspects-170606133459.pdf
 
lect 1-2.pdf
lect 1-2.pdflect 1-2.pdf
lect 1-2.pdf
 
GIS VIMAL SUBBU.17.08.2022.pptx
GIS VIMAL SUBBU.17.08.2022.pptxGIS VIMAL SUBBU.17.08.2022.pptx
GIS VIMAL SUBBU.17.08.2022.pptx
 
Iirs lecure notes for Remote sensing –An Overview of Decision Maker
Iirs lecure notes for Remote sensing –An Overview of Decision MakerIirs lecure notes for Remote sensing –An Overview of Decision Maker
Iirs lecure notes for Remote sensing –An Overview of Decision Maker
 
REMOTE SENSING
REMOTE SENSINGREMOTE SENSING
REMOTE SENSING
 
Presentation on Aerosols, cloud properties
Presentation on Aerosols, cloud properties Presentation on Aerosols, cloud properties
Presentation on Aerosols, cloud properties
 
Water-Body Area Extraction From High Resolution Satellite Images-An Introduct...
Water-Body Area Extraction From High Resolution Satellite Images-An Introduct...Water-Body Area Extraction From High Resolution Satellite Images-An Introduct...
Water-Body Area Extraction From High Resolution Satellite Images-An Introduct...
 
Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...
Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...
Application of spectral remote sensing in agronomic decision by Dr.V.Harihara...
 

More from Chongtham Allaylay Devi

More from Chongtham Allaylay Devi (11)

interaction of different stress and its impact on crop
interaction of different stress and its impact on crop interaction of different stress and its impact on crop
interaction of different stress and its impact on crop
 
Crop modeling and stress
Crop modeling and stressCrop modeling and stress
Crop modeling and stress
 
Rootstock
Rootstock Rootstock
Rootstock
 
Unfruitful
UnfruitfulUnfruitful
Unfruitful
 
Mapping
MappingMapping
Mapping
 
Seed respiration 2
Seed respiration 2Seed respiration 2
Seed respiration 2
 
Unfruitful
UnfruitfulUnfruitful
Unfruitful
 
Climate change
Climate changeClimate change
Climate change
 
crop improvement on apple crop
crop improvement on apple cropcrop improvement on apple crop
crop improvement on apple crop
 
Impacts of climate change on important fruit crops of Rosaceae family
Impacts of climate change on important fruit crops of Rosaceae familyImpacts of climate change on important fruit crops of Rosaceae family
Impacts of climate change on important fruit crops of Rosaceae family
 
Seed dormancy in tropical fruit crops and measure to overcome it
Seed dormancy in tropical fruit crops and measure to overcome itSeed dormancy in tropical fruit crops and measure to overcome it
Seed dormancy in tropical fruit crops and measure to overcome it
 

Recently uploaded

Industrial Training Report- AKTU Industrial Training Report
Industrial Training Report- AKTU Industrial Training ReportIndustrial Training Report- AKTU Industrial Training Report
Industrial Training Report- AKTU Industrial Training Report
Avinash Rai
 
The basics of sentences session 4pptx.pptx
The basics of sentences session 4pptx.pptxThe basics of sentences session 4pptx.pptx
The basics of sentences session 4pptx.pptx
heathfieldcps1
 
Neurulation and the formation of the neural tube
Neurulation and the formation of the neural tubeNeurulation and the formation of the neural tube
Neurulation and the formation of the neural tube
SaadHumayun7
 

Recently uploaded (20)

Industrial Training Report- AKTU Industrial Training Report
Industrial Training Report- AKTU Industrial Training ReportIndustrial Training Report- AKTU Industrial Training Report
Industrial Training Report- AKTU Industrial Training Report
 
50 ĐỀ LUYỆN THI IOE LỚP 9 - NĂM HỌC 2022-2023 (CÓ LINK HÌNH, FILE AUDIO VÀ ĐÁ...
50 ĐỀ LUYỆN THI IOE LỚP 9 - NĂM HỌC 2022-2023 (CÓ LINK HÌNH, FILE AUDIO VÀ ĐÁ...50 ĐỀ LUYỆN THI IOE LỚP 9 - NĂM HỌC 2022-2023 (CÓ LINK HÌNH, FILE AUDIO VÀ ĐÁ...
50 ĐỀ LUYỆN THI IOE LỚP 9 - NĂM HỌC 2022-2023 (CÓ LINK HÌNH, FILE AUDIO VÀ ĐÁ...
 
How to the fix Attribute Error in odoo 17
How to the fix Attribute Error in odoo 17How to the fix Attribute Error in odoo 17
How to the fix Attribute Error in odoo 17
 
“O BEIJO” EM ARTE .
“O BEIJO” EM ARTE                       .“O BEIJO” EM ARTE                       .
“O BEIJO” EM ARTE .
 
Application of Matrices in real life. Presentation on application of matrices
Application of Matrices in real life. Presentation on application of matricesApplication of Matrices in real life. Presentation on application of matrices
Application of Matrices in real life. Presentation on application of matrices
 
Post Exam Fun(da) Intra UEM General Quiz 2024 - Prelims q&a.pdf
Post Exam Fun(da) Intra UEM General Quiz 2024 - Prelims q&a.pdfPost Exam Fun(da) Intra UEM General Quiz 2024 - Prelims q&a.pdf
Post Exam Fun(da) Intra UEM General Quiz 2024 - Prelims q&a.pdf
 
Basic Civil Engg Notes_Chapter-6_Environment Pollution & Engineering
Basic Civil Engg Notes_Chapter-6_Environment Pollution & EngineeringBasic Civil Engg Notes_Chapter-6_Environment Pollution & Engineering
Basic Civil Engg Notes_Chapter-6_Environment Pollution & Engineering
 
The Art Pastor's Guide to Sabbath | Steve Thomason
The Art Pastor's Guide to Sabbath | Steve ThomasonThe Art Pastor's Guide to Sabbath | Steve Thomason
The Art Pastor's Guide to Sabbath | Steve Thomason
 
The basics of sentences session 4pptx.pptx
The basics of sentences session 4pptx.pptxThe basics of sentences session 4pptx.pptx
The basics of sentences session 4pptx.pptx
 
Neurulation and the formation of the neural tube
Neurulation and the formation of the neural tubeNeurulation and the formation of the neural tube
Neurulation and the formation of the neural tube
 
Matatag-Curriculum and the 21st Century Skills Presentation.pptx
Matatag-Curriculum and the 21st Century Skills Presentation.pptxMatatag-Curriculum and the 21st Century Skills Presentation.pptx
Matatag-Curriculum and the 21st Century Skills Presentation.pptx
 
Post Exam Fun(da) Intra UEM General Quiz - Finals.pdf
Post Exam Fun(da) Intra UEM General Quiz - Finals.pdfPost Exam Fun(da) Intra UEM General Quiz - Finals.pdf
Post Exam Fun(da) Intra UEM General Quiz - Finals.pdf
 
Incoming and Outgoing Shipments in 2 STEPS Using Odoo 17
Incoming and Outgoing Shipments in 2 STEPS Using Odoo 17Incoming and Outgoing Shipments in 2 STEPS Using Odoo 17
Incoming and Outgoing Shipments in 2 STEPS Using Odoo 17
 
How to Manage Notification Preferences in the Odoo 17
How to Manage Notification Preferences in the Odoo 17How to Manage Notification Preferences in the Odoo 17
How to Manage Notification Preferences in the Odoo 17
 
An Overview of the Odoo 17 Discuss App.pptx
An Overview of the Odoo 17 Discuss App.pptxAn Overview of the Odoo 17 Discuss App.pptx
An Overview of the Odoo 17 Discuss App.pptx
 
NCERT Solutions Power Sharing Class 10 Notes pdf
NCERT Solutions Power Sharing Class 10 Notes pdfNCERT Solutions Power Sharing Class 10 Notes pdf
NCERT Solutions Power Sharing Class 10 Notes pdf
 
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptx
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxStudents, digital devices and success - Andreas Schleicher - 27 May 2024..pptx
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptx
 
[GDSC YCCE] Build with AI Online Presentation
[GDSC YCCE] Build with AI Online Presentation[GDSC YCCE] Build with AI Online Presentation
[GDSC YCCE] Build with AI Online Presentation
 
Gyanartha SciBizTech Quiz slideshare.pptx
Gyanartha SciBizTech Quiz slideshare.pptxGyanartha SciBizTech Quiz slideshare.pptx
Gyanartha SciBizTech Quiz slideshare.pptx
 
size separation d pharm 1st year pharmaceutics
size separation d pharm 1st year pharmaceuticssize separation d pharm 1st year pharmaceutics
size separation d pharm 1st year pharmaceutics
 

Assessing stress by using remote sensing

  • 1. 1 PRESENTED BY, Ch. Allaylay Devi PhD. (Hort.) 1st Year Dept. of FSc.
  • 2. Introduction • Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation. • Remote sensing is used in numerous fields, including geography, land surveying and most Earth Science disciplines (for example, hydrology, ecology, oceanography, glaciology, geology) • It also has military, intelligence, commercial, economic, planning, and humanitarian applications. 2
  • 3. Remote sensing • “Remote sensing" generally refers to the use of satellite- or aircraft-based sensor technologies to detect and classify objects on Earth, including on the surface and in the atmosphere and oceans, based on propagated signals (e.g. electromagnetic radiation). • It may be split into active and passive remote sensing • “Active" remote sensing (i.e., when a signal is emitted by a satellite or aircraft and its reflection by the object is detected by the sensor). • “Passive" remote sensing (i.e., when the reflection of sunlight is detected by the sensor)
  • 4. Techniques of remote sensing and its applications • Conventional radar is mostly associated with aerial traffic control, early warning, and certain large scale meteorological data. • Doppler radar is used by local law enforcements’ monitoring of speed limits and in enhanced meteorological collection such as wind speed and direction within weather systems in addition to precipitation location and intensity. • Other types of active collection includes plasmas in the ionosphere. • Interferometric synthetic aperture radar is used to produce precise digital elevation models of large scale terrain (RADARST, TerraSAR-X, Magellan). • Laser and radar altimeters on satellites have provided a wide range of data. By measuring the bulges of water caused by gravity, they map features on the seafloor to a resolution of a mile or so.
  • 5. • By measuring the height and wavelength of ocean waves, the altimeters measure wind speeds and direction, and surface ocean currents and directions. • Ultrasound (acoustic) and radar tide gauges measure sea level, tides and wave direction in coastal and offshore tide gauges. • Light detection and ranging (LIDAR) is well known in examples of weapon ranging, laser illuminated homing of projectiles. It is used to detect and measure the concentration of various chemicals in the atmosphere, while airborne LIDAR can be used to measure heights of objects and features on the ground more accurately than with radar technology. Vegetation remote sensing is a principal application of LIDAR.
  • 6. • Radiometers and photometers are the most common instrument in use, collecting reflected and emitted radiation in a wide range of frequencies. The most common are visible and infrared sensors, followed by microwave, gamma ray and rarely, ultraviolet. They may also be used to detect the emission spectra of various chemicals, providing data on chemical concentrations in the atmosphere. • Stereographic pairs of aerial photographs have often been used to make topographic maps by imagery and terrain analysts in trafficability and highway departments for potential routes, in addition to modelling terrestrial habitat features.
  • 7. • Simultaneous multi-spectral platforms such as Landsat have been in use since the 1970s. • These thematic mappers take images in multiple wavelengths of electro- magnetic radiation (multi-spectral) and are usually found on Earth observation satellites, including (for example) the Landsat program or the IKONOS satellite. • Maps of land cover and land use from thematic mapping can be used to prospect for minerals, detect or monitor land usage, detect invasive vegetation, deforestation, and examine the health of indigenous plants and crops, including entire farming regions or forests. • Landsat images are used by regulatory agencies such as KYDOW to indicate water quality parameters including Secchi depth, chlorophyll a density and total phosphorus content. Weather satellites are used in meteorology and climatology.
  • 8. • Hyperspectral imaging produces an image where each pixel has full spectral information with imaging narrow spectral bands over a contiguous spectral range. Hyperspectral imagers are used in various applications including mineralogy, biology, defence, and environmental measurements. • Within the scope of the combat against desertification, remote sensing allows to follow up and monitor risk areas in the long term, to determine desertification factors, to support decision-makers in defining relevant measures of environmental management, and to assess their impacts
  • 9. Methods for monitoring indicators of vegetation condition Spatial and temporal scales of monitoring • It is a site-based monitoring programmes having a long a history of application (e.g. Lawley et al., 2013 ; Sinclair, 2005), and still being commonly used today. • It involves selecting sites from within homogenous patches of vegetation of the same community type and site history. • The majority of site-based assessments are quadrat-based where detailed information is collected about the compositional, structural, and functional attributes of a site. • In some cases landscape metrics have also been added into overall measures, and benchmarked scores are combined to give an overall condition index for individual patches of sampled vegetation (Department, 2011; Michaels, 2006; Parkes et al., 2003). • It predominantly measure structural and compositional indicators of vegetation condition, with less emphasis on indicators of function.
  • 10. Assessed stress by utilising remote sensing Detection of plant water stress using remote sensing  These technologies acquire many hundreds of spectral bands across the spectrum from 400 nm to 2 500 nm, using satellite, airborne or hand-held devices.  The spectral characteristics of vegetation are governed primarily by scattering and absorption characteristics of the leaf internal structure and biochemical constituents, such as pigments, water, nitrogen, cellulose and lignin (Asner, 1998; Coops et al., 2002). Pigments are the main determinants controlling the spectral responses of leaves in the visible wavelengths (Gaussman, 1977).  Chlorophyll pigment content, in particular, is directly associated with photosynthetic capacity and productivity (Gaussman, 1977; Curran et al., 1992).  Reduced concentrations of chlorophyll are indicative of plant stress (Curran et al., 1992).
  • 11. Spectral indicators of plant chlorophyll content • In stressed vegetation, leaf chlorophyll content decreases, thereby changing the proportion of light-absorbing pigments, leading to a reduction in the overall absorption of light (Murtha, 1982; Zarco-Tejada et al., 2000). • These changes affect the spectral reflectance signatures of plants through a reduction in green reflection and an increase in red and blue reflections, resulting in changes in the normal spectral reflectance patterns of plants (Murtha, 1982; Zarco-Tejada et al., 2000). • Thus, detecting changes from the normal (unstressed) spectral reflectance patterns is the key to interpreting plant stress.
  • 12. Spectral indicators of plant water content • Plant water content at the leaf and canopy scales is often estimated using specific spectral reflectance bands and spectral reflectance indices from near infrared, middle infrared (MIR) and short-wave infrared (SWIR) regions of the electromagnetic spectrum (Tucker, 1980; Hunt and Chun-Jiang et al., 2006). • NIR and MIR spectral bands are highly correlated to water content of vegetation and soils (Tucker, 1980; Hunt and Rock, 1989; Musick and Pelletier, 1986; 1988). • Spectral bands from these regions have been used to delineate stressed trees from non-stressed trees. • In these regions of the electromagnetic spectrum, leaf water content has been remotely assessed using bands 1 550 nm to 1 750 nm (Tucker, 1980) • MIR reflectance increased with decreasing leaf water content.
  • 13. Predawn leaf water potential • Predawn leaf water potential measurements, often undertaken with a pressure chamber, are useful for determining plant water stress. • At predawn, xylem water potential has equilibrated with soil water potential after a night of negligible transpiration. • At this time, plant water potential is usually at its minimum for the day (Cleary and Zaerr, 1984). • The pressure chamber is most commonly used for estimating leaf water potential, having the advantage of simplicity, reliability, instantaneous measurements, low capital cost and portability (Scholander et al., 1965; Boyer, 1968; Ritchie and Hinckley, 1975). • It is commonly used as a plant water stress indicator and has also been used to describe the water status of different species within a habitat
  • 14. Leaf chlorophyll fluorescence • Chlorophyll fluorescence measurements can be described using the typical phases of a temporary fluorescence signal or transient. • Therefore, this photosynthetic apparatus has been recognised as being a good indicator of stress and stress adaptation of a plant and is associated with the measurement of chlorophyll fluorescence (Salisbury and Ross, 1992; Strasser and Tsmilli-Michael, 2001; Strasser et al., 2001). • Also, because changes in chlorophyll fluorescence may occur before any physical signs of tissue or chlorophyll deterioration are manifested in the plant, stress can be detected before the onset of physical damage (Lichtenthaler et al., 2007).
  • 16. Conclusion • With the launch and continuous availability of multi-spectral (visible, near-infrared) sensors on polar orbiting earth observation satellites (Landsat, SPOT, IRS, etc.) remote sensing (RS) data has become an important tool for yield modeling. • Remote sensing research has identified several individual spectral bands and vegetation spectral reflectance indices which have been used to detect plant water stress. • Depending upon the scale at which an investigation is being undertaken, it is recommended that a practical approach to assessing plant water stress is adopted through the use of at least one ground-based measurement.

Editor's Notes

  1. Govender, et al., 2009