Remote Sensing & Landscape
Ecology: an overview
Ranjeet John
02/11/09
• Remote sensing is the small or largescale 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 Bruggioni
http://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://ls7pm3.gsfc.nasa.gov/Images/etmpics/bands.gif
http://earthobservatory.nasa.gov/Features/LandCover/land_cover_2.php
Portions of the EM
spectrum that can
pass through the
atmosphere with little
or no attenuation are
referred to as
atmospheric windows
The 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
Atmospheric windows
Terra Orbit
Polar sun synchronous orbit
http://modis.gsfc.nasa.gov/gallery/#
http://landsathandbook.gsfc.nasa.gov/handbook/handbook_htmls/chapter1/chapter1.html
TM/Landsat, MODIS/Terra
SPOT (France), IRS (India)
Dichroic lens/prism
Sensor motion
Across track or whiskbroom
Sensor motion
Along track or whiskbroom
From Jensen, J. (2000) Remote sensing: and Earth resource perspective, p. 184
From: http://ceos.cnes.fr:8100/cdrom/ceos1/irsd/pages/datacq4.htm & J. Jensen (2000)
Path
126
125
124
35
Study area
2007/05/19
36
2007/09/22
2007/08/20
37
2007/09/15
Row
MODIS 1km (LST, LAI/FPAR, GPP/NPP)
MODIS 500m water stress (NDSVI, LSWI)
MODIS 250m EVI
L7, 60m
L7,30
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
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)
http://cwcaribbean.aoml.noaa.gov/bilko/module7/lesson3/images/Image12.gif
Rd
Ra
target
Rb
target
Rc
target
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
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
Radiance, L
Offset assumed to be atmospheric
path radiance (plus dark current
signal)
Lmax
Regression line L = G*DN + O (+)
Target DN values
DN
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
https://zulu.ssc.nasa.gov/mrsid/tutorial/Landsat%20Tutorial-V1.html
5,4,2 false color
https://zulu.ssc.nasa.gov/mrsid/tutorial/Landsat%20Tutorial-V1.html
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
Image Processing Flow Chart
Radiometric correction
Raw DN
Radiance
Reflectance
(TOA)
Geometric correction
Recoded to Anderson’s
Level I
MODTRAN
4
Reflectance
(Surface)
Rectified
image
Unsupervised
Classification
Image Processing Flow Chart (for ETM+)
Radiometric correction
Raw DN
Radiance
Reflectance
(TOA)
Geometric correction
MODTRAN
4
Reflectance
(Surface)
Rectified
image
NDVI
Fract cover
(green)
http://www.umass.edu/landeco/research/fragstats/fragstats.html
0
1.5
3
6 Kilometers
Oak Opening NLCD 2001
0
1.5
3
6 Kilometers
Oak Opening NLCD 1992
Oak Opening NLCD 1992
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
0
2
4
8 Kilometers
Woody Wetlands
Emergent Herbaceous Wetlands
Oak Opening NLCD 2001
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
0
2
4
8 Kilometers
Woody Wetlands
Emergent Herbaceous Wetlands
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
0
0.5
1
2 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
0
0.5
1
2 Kilometers
Land Cover/Use 1992-2001
1500
NLCD 1992
1000
NLCD 2001
500
0
Land Cover/Use
change in Oak
Opening and
Maumee state
forests (1992-2001)
op
en
w
De ate
ve r
De Bar lo p
cid r en ed
u
Ev ou Lan
er s F d
gr
e e or e
G
n st
ra
M
F
ss
la ixed ore
s
nd
/ H Fo t
e r res
b
t
Pa ace
Cu stu ou
ltiv r e s
W
a /H
Em o o te d ay
C
er dy
ge W rop
e
nt
s
He tlan
rb ds
ac
eo
..
Land Cover/Use 1992-2001
NLCD classes
100
2001
0.27
6.06
0.06
64.95
20.60
0.55
2.62
3.00
1.84
0.06
80
60
NLCD 1992
40
NLCD 2001
20
0
op
en
w
De ate
ve r
De Bar lo p
cid r en ed
u
L
Ev ou an
er s F d
gr
e e or e
G
n st
ra
ss Mix Fo
la
r
nd ed est
F
/H
e r o re
st
b
Pa ace
Cu stu ou
ltiv r e s
W
a /H
Em o o te d ay
C
er dy
ge W rop
e
nt
s
He tlan
rb ds
ac
eo
..
LULC
1992
open water
0.74
Developed
0.14
Barren Land
0.00
Deciduous Forest
63.58
Evergreen Forest
12.55
Mixed Forest
0.09
Pasture/Hay
4.46
Cultivated Crops
6.42
Woody Wetlands
11.75
Emergent Herbaceous Wetlands
0.28
Percentage
Hectares
2000
NLCD classes
Class Properties File
ClassID
11
20
31
41
42
43
81
82
91
92
ClassName
open water
Developed
Barren Land
Deciduous Forest
Evergreen Forest
Mixed Forest
Pasture/Hay
Cultivated Crops
Woody Wetlands
Emergent Herbaceous Wetlands
Status
t
t
t
t
t
t
t
t
t
t
isBackground
f
f
f
f
f
f
f
f
f
f
LID
TYPE
NP
PD
LPI
CLUMPY IJI
AI
F:\oakopening\oakopen\oak01_sign.img
0
4
0.0454 63.9861
0.9679 69.8777 99.1013
F:\oakopening\oakopen\oak01_sign.img
Developed
61
0.6919
0.5502
0.5168 59.5172 52.4985
F:\oakopening\oakopen\oak01_sign.img
Deciduous Forest
41
0.465 12.3667
0.8871 70.0894 90.7592
F:\oakopening\oakopen\oak01_sign.img
Cultivated Crops
45
0.5104
0.3266
0.7953 54.5533 79.6974
F:\oakopening\oakopen\oak01_sign.img
Grassland/Herbaceous
21
0.2382
0.0459
0.6467 65.9834 64.7273
F:\oakopening\oakopen\oak01_sign.img
Emergent Herbaceous Wetlands
2
0.0227
0.0112
0.4799 47.5967
48
F:\oakopening\oakopen\oak01_sign.img
Woody Wetlands
21
0.2382
0.1205
0.6208
7.3539 62.2798
F:\oakopening\oakopen\oak01_sign.img
Evergreen Forest
87
0.9867
0.7972
0.8159 42.2191 82.6532
F:\oakopening\oakopen\oak01_sign.img
Pasture/Hay
67
0.7599
0.3001
0.654 58.8085 65.6566
F:\oakopening\oakopen\oak01_sign.img
open water
4
0.0454
0.0235
0.6404 48.4813 64.0625
F:\oakopening\oakopen\oak01_sign.img
Barren Land
1
0.0113
0.0174
0.92 25.4476
92
F:\oakopening\oakopen\oak92_sign.img
0
4
F:\oakopening\oakopen\oak92_sign.img
Pasture/Hay
406
F:\oakopening\oakopen\oak92_sign.img
Cultivated Crops
248
F:\oakopening\oakopen\oak92_sign.img
Deciduous Forest
164
F:\oakopening\oakopen\oak92_sign.img
Evergreen Forest
226
F:\oakopening\oakopen\oak92_sign.img
Woody Wetlands
557
F:\oakopening\oakopen\oak92_sign.img
open water
143
F:\oakopening\oakopen\oak92_sign.img
Emergent Herbaceous Wetlands
43
F:\oakopening\oakopen\oak92_sign.img
Developed
25
0.0454
4.6048
2.8128
1.8601
2.5633
6.3174
1.6219
0.4877
0.2835
63.9861
0.0796
0.3195
13.1333
0.4073
0.1358
0.0092
0.0061
0.0031
0.9679
0.3421
0.6195
0.774
0.6969
0.4538
0.1096
0.2347
0.206
65.8123
58.8283
55.8102
74.1094
46.2309
35.1807
40.0572
69.1981
65.2024
99.1013
35.0294
62.631
81.4224
70.7508
47.1722
11.1406
23.5294
20.6349