Remote Sensing & Landscape Ecology: an overview Ranjeet John 02/11/09.

Remote Sensing & Landscape Ecology: an overview

Ranjeet John

02/11/09

• Remote sensing is the small or large-scale acquisition of information of an object or phenomenon, by the use of either recording or real-time sensing device(s) that is not in physical or intimate contact with the object. (from Wikipedia)

the term, “remote sensing,” was first introduced in 1960 by Evelyn L. Pruitt of the U.S. Office of Naval Research.

http://employees.oneonta.edu/baumanpr/geosat2/RSHistory/HistoryRSPart1.htm

• Remote Sensing in the most generally accepted meaning refers to instrument-based techniques employed in the acquisition and measurement of spatially organized (most commonly, geographically distributed) data/information on some property(ies) (spectral; spatial; physical) of an array of target points (pixels) within the sensed scene that correspond to features, objects, and materials, doing this by applying one or more recording devices not in physical, intimate contact with the item(s) under surveillance (thus at a finite distance from the observed target, in which the spatial arrangement is preserved); techniques involve amassing knowledge pertinent to the sensed scene (target) by utilizing electromagnetic radiation, force fields, or acoustic energy sensed by recording cameras, radiometers and scanners, lasers, radio frequency receivers, radar systems, sonar, thermal devices, sound detectors, seismographs, magnetometers, gravimeters, scintillometers, and other instruments.

NASA remote sensing tutorial (http://rst.gsfc.nasa.gov/Intro/Part2_1.html)

http://www.gwu.edu/~nsarchiv/nsa/cuba_mis_cri/photos.htm

• 65 feet long …

• 5 S’s of PI (shape, size, shadow, site, shade)

• "If you walk in a field in the early morning, you create a path through the field when you disturb the dew. This could be seen from 100 miles up in space. We see things the groundling is not cognizant of at all on Earth."

- Dino Bruggionihttp://www.pbs.org/wgbh/nova/spiesfly/brugioni.html

http://airphotos.nrcan.gc.ca/photos101/photos101_info_e.php

SATELLITE IMAGERY

• Landscape Scale: Landsat 7/ETM+ (30m)

• Regional Scale:Terra/ MODIS (1000m, 500m, and 250m)

10 / 2003

Types of Remote sensing

• Active: energy generated from within the sensor system is beamed outward, and the fraction returned is measured e.g., radar

• Passive (optical): energy leading to radiation received comes from an external source, e.g., Sun

from your reading, can you give me examples for the above..

• Spatial resolution is commonly expressed as the most closely spaced line-pairs per unit distance that can be distinguished.

• Spectral res. : can be defined by the limits of the continuous wavelengths (or frequencies) that can be detected in the spectrum

• Radiometric res. : relates to levels of quantization that can be detected or be established to improve scene quality (for eg. tonal contrast or 256 shades of grey= 8 bit vs human eye = 16 levels) . 1 bit = 2 quantization levels

• Temporal res. : refers to the length of time it takes for the satellite to complete one entire orbit cycle. However, owing to possible overlaps of adjacent swaths, the repeat cycle may change. If a satellite has a pointing capability, the temporal resolution could be higher.

NASA remote sensing tutorial (http://rst.gsfc.nasa.gov/Intro/Part2_1.html)

http://landsathandbook.gsfc.nasa.gov/handbook.html

http://www.sat.dundee.ac.uk/sensors.html

http://earthobservatory.nasa.gov/Features/LandCover/land_cover_2.php

http://ls7pm3.gsfc.nasa.gov/Images/etmpics/bands.gif

Atmospheric windows

Portions of the EM spectrum that can pass through the atmosphere with little or no attenuation are referred to as atmospheric windowsThe figure shows areas of the spectrum that can pass through the atmosphere without attenuation (peaks) and areas that are attenuated (valleys)

http://www.geo.unizh.ch/~kaeaeb/glims/glims.html

http://modis.gsfc.nasa.gov/gallery/#

Terra Orbit

Polar sun synchronous orbit

http://landsathandbook.gsfc.nasa.gov/handbook/handbook_htmls/chapter1/chapter1.html

Sensor motion

Dichroic lens/prism

Across track or whiskbroom

Sensor motion

From: http://ceos.cnes.fr:8100/cdrom/ceos1/irsd/pages/datacq4.htm & J. Jensen (2000)

From Jensen, J. (2000) Remote sensing: and Earth resource perspective, p. 184

TM/Landsat, MODIS/Terra

SPOT (France), IRS (India)

Along track or whiskbroom

126 125 124

35

36

37

Path

Row

2007/09/22

2007/09/15

2007/05/19

2007/08/20

Study area

MODIS 1km (LST, LAI/FPAR, GPP/NPP)

MODIS 500m water stress (NDSVI, LSWI)

MODIS 250m EVI

L7,30

L7, 60m

Image processing (work flow)

• Radiometric correction - atmospheric correction• Geometric correction - rectification & georeferencing• Display & Enhancement - Contrast stretching• Information extraction – image classification (supervised/unsupervised) data mining, feature extraction, spectral vegetation indices (SVIs)

• Analysis outside RS/GIS, data staged in text files/excel from

imagery and analyzed in statistics package

Radiometric correction

• Raw DN: Digital number (0-255), for 8 bit

• Radiance: is the sun’s energy reflected by a target, measured in optical units of radiance (watts/m2)

radiance = slope * (DN) + intercept

irradiance: sun’s energy incident on target

• Reflectance: is defined as the ratio of the radiance to irradiance defines the true reflectance of the target

reflectance = radiance / irradiance

computed as % reflectance

http://www.yale.edu/ceo/Documentation/ComputingReflectanceFromDN.pdf

http://cwcaribbean.aoml.noaa.gov/bilko/module7/lesson3/images/Image12.gif

the dominant atmospheric effect on remote sensing is “path radiance”; the scattering of radiation from the sun’s beam into the direction of the satellite by air molecules or by suspended particles.

Some Atm. Correction methods

5s, 6s, Atcorr. MODTRAN 4 or the simple Dark object subtraction, or Psuedo-invariant object correction (subtract and normalize near black bodies & white body object pixels in the image)

target reflectance is a f ( ) of •Atmospheric irradiance (path radiance: Ra)

•Reflectance beyond target scattered into path (Ra)

•Diffuse atmospheric irradiance (scattered on target: Rc)

•Multiple-scattered surface-atmosphere interaction (Rd)

From: http://www.geog.ucl.ac.uk/~mdisney/phd.bak/final_version/final_pdf/chapter2a.pdf

Ra

target

Rb

target

Rc

target

Rd

target

Simple atm. Corr. – empirical line correction (ELC) method

– targets of “known”, low and high reflectance targets in one channel are chosen

e.g. non-turbid water & desert (white sands), or dense dark vegetation & snow

– Assuming linear detector response, radiance, L = gain * DN + offset

– e.g. L = DN(Lmax - Lmin)/255 + Lmin

DN

Radiance, L

Target DN values

Regression line L = G*DN + O (+)

Offset assumed to be atmospheric path radiance (plus dark current signal)

Lmax

Lmin

www2.geog.ucl.ac.uk/~mdisney/teaching/PPRS/PPRS_5/principles5.ppt

Geometric correction

• Registration: is the process of making an image conform to another image (or map).

• Rectification/Georeferencing: The process of assigning map coordinates to image data.

• Geocoding: A special case of rectification that includes scaling to a uniform, standard pixel and to a particular map projection.

• Orthorectification: a form of rectification that corrects for terrain displacement using DEMs.

3,2,1 true color

https://zulu.ssc.nasa.gov/mrsid/tutorial/Landsat%20Tutorial-V1.html

4,3,2 false color


5,4,2 false color


Band 3: red

Band 4: NIR

Band 5: SWIR

NDVI = (NIR — VIS)/(NIR + VIS)

http://earthobservatory.nasa.gov/Library/MeasuringVegetation/

http://www2.geog.ucl.ac.uk/~plewis/geog2021/classificationPractical/

Image classification

• Land cover is not the same Land use– what’s there: Land cover – How is the land being used: Land use– i.e. Anthropogenic modification of natural

cover

• Eg.– grass is land cover; pasture and recreational

parks are land uses of grass

• Supervised Classification: : requires the RS analyst to select training areas where she/he knows what is on the ground and inputs these signature/training pixels to obtain a classified image using one of these three classifiers – Parallelpiped– Minimum distance to mean– Maximum likelihood

Unsupervised Classification

• Rather than defining training sets, we do not define any classes beforehand (thus avoiding user bias).

• Instead, the software uses statistical approaches (below) to divide the n-dimensional space into clusters with the best separation

• Iterative Self-Organizing Data Analysis (Isodata) Technique

• we then assign class names to the clusters

Raw DNRadiance

Reflectance(TOA)

Image Processing Flow Chart

Reflectance(Surface)

MODTRAN4


Rectified image


Unsupervised Classification

Recoded to Anderson’sLevel I

Raw DNRadiance

Reflectance(TOA)

Image Processing Flow Chart (for ETM+)

Reflectance(Surface)

MODTRAN4


Rectified image


NDVI

Fract cover(green)

http://www.umass.edu/landeco/research/fragstats/fragstats.html

Oak Opening NLCD 20010 3 61.5 Kilometers

Oak Opening NLCD 19920 3 61.5 Kilometers

NLCD

Open Water

Low Intensity Residential

High Intensity Residential

Commercial/Industrial/Transportation

Bare Rock/Sand/Clay

Quarries/Strip Mines/Gravel Pits

Transitional

Deciduous Forest

Evergreen Forest

Mixed Forest

Grasslands/Herbaceous

Pasture/Hay

Row Crops

Urban/Recreational Grasses

Woody Wetlands

Emergent Herbaceous Wetlands

Oak Opening NLCD 1992

0 4 82 Kilometers

NLCD

Open Water




Bare Rock/Sand/Clay


Transitional

Deciduous Forest

Evergreen Forest

Mixed Forest


Pasture/Hay

Row Crops


Woody Wetlands


Oak Opening NLCD 2001

0 4 82 Kilometers

NLCD

Open Water




Bare Rock/Sand/Clay


Transitional

Deciduous Forest

Evergreen Forest

Mixed Forest


Pasture/Hay

Row Crops


Woody Wetlands


0 1 20.5 Kilometers

Land Cover/Use change in Oak Opening and Maumee state forests (1992-2001)

LULC 1992 2001open water 0.74 0.27Developed 0.14 6.06Barren Land 0.00 0.06Deciduous Forest 63.58 64.95Evergreen Forest 12.55 20.60Mixed Forest 0.09 0.55Pasture/Hay 4.46 2.62Cultivated Crops 6.42 3.00Woody Wetlands 11.75 1.84Emergent Herbaceous Wetlands0.28 0.06

ClassID ClassName Status isBackground11 open water t f20 Developed t f31 Barren Land t f41 Deciduous Forest t f42 Evergreen Forest t f43 Mixed Forest t f81 Pasture/Hay t f82 Cultivated Crops t f91 Woody Wetlands t f92 Emergent Herbaceous Wetlands t f

Class Properties File

LID TYPE NP PD LPI CLUMPY IJI AIF:\oakopening\oakopen\oak01_sign.img 0 4 0.0454 63.9861 0.9679 69.8777 99.1013F:\oakopening\oakopen\oak01_sign.imgDeveloped 61 0.6919 0.5502 0.5168 59.5172 52.4985F:\oakopening\oakopen\oak01_sign.imgDeciduous Forest 41 0.465 12.3667 0.8871 70.0894 90.7592F:\oakopening\oakopen\oak01_sign.imgCultivated Crops 45 0.5104 0.3266 0.7953 54.5533 79.6974F:\oakopening\oakopen\oak01_sign.imgGrassland/Herbaceous 21 0.2382 0.0459 0.6467 65.9834 64.7273F:\oakopening\oakopen\oak01_sign.imgEmergent Herbaceous Wetlands2 0.0227 0.0112 0.4799 47.5967 48F:\oakopening\oakopen\oak01_sign.imgWoody Wetlands 21 0.2382 0.1205 0.6208 7.3539 62.2798F:\oakopening\oakopen\oak01_sign.imgEvergreen Forest 87 0.9867 0.7972 0.8159 42.2191 82.6532F:\oakopening\oakopen\oak01_sign.imgPasture/Hay 67 0.7599 0.3001 0.654 58.8085 65.6566F:\oakopening\oakopen\oak01_sign.imgopen water 4 0.0454 0.0235 0.6404 48.4813 64.0625F:\oakopening\oakopen\oak01_sign.imgBarren Land 1 0.0113 0.0174 0.92 25.4476 92

F:\oakopening\oakopen\oak92_sign.img 0 4 0.0454 63.9861 0.9679 65.8123 99.1013F:\oakopening\oakopen\oak92_sign.imgPasture/Hay 406 4.6048 0.0796 0.3421 58.8283 35.0294F:\oakopening\oakopen\oak92_sign.imgCultivated Crops 248 2.8128 0.3195 0.6195 55.8102 62.631F:\oakopening\oakopen\oak92_sign.imgDeciduous Forest 164 1.8601 13.1333 0.774 74.1094 81.4224F:\oakopening\oakopen\oak92_sign.imgEvergreen Forest 226 2.5633 0.4073 0.6969 46.2309 70.7508F:\oakopening\oakopen\oak92_sign.imgWoody Wetlands 557 6.3174 0.1358 0.4538 35.1807 47.1722F:\oakopening\oakopen\oak92_sign.imgopen water 143 1.6219 0.0092 0.1096 40.0572 11.1406F:\oakopening\oakopen\oak92_sign.imgEmergent Herbaceous Wetlands43 0.4877 0.0061 0.2347 69.1981 23.5294F:\oakopening\oakopen\oak92_sign.imgDeveloped 25 0.2835 0.0031 0.206 65.2024 20.6349

Remote Sensing & Landscape Ecology: an overview Ranjeet John 02/11/09.

Documents

Transcript of Remote Sensing & Landscape Ecology: an overview Ranjeet John 02/11/09.