Intel 304

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Resolutions of Remote Sensing

1. Spatial (what area and how detailed)

2. Spectral (what colors – bands)

3. Temporal (time of day/season/year)

4. Radiometric (color depth)

Spatial Resolution describes how much detail in a photographic image is visible to the human eye.

The ability to "resolve," or separate, small details is one way of describing what we call spatial resolution.

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Spatial resolution of images acquired by satellite sensor systems is usually expressed in meters.

For example, we often speak of Landsat as having “30- meter" resolution, which means that two objects, thirty meters long or wide, sitting side by side, can be separated (resolved) on a Landsat image.

Other sensors have lower or higher spatial resolutions.

Comparison of Landsat Sensors

Thematic Mapper (TM) Landsat 4 and 5

Enhanced Thematic Mapper Plus (ETM+)

Landsat 7

Multispectral Scanner (MSS)

Landsat 1-5 Spectral Resolution (µm)

1. 0.45-0.52 (B) 2. 0.52-0.60 (G) 3. 0.63-0.69 (R) 4. 0.76-0.90 (NIR) 5. 1.55-1.75 (MIR) 6. 2.08-2.35 (MIR) 7. 10.4-12.5 (TIR)

1. 0.45-0.52 2. 0.53-0.61 3. 0.63-0.69 4. 0.78-0.90 5. 1.55-1.75 6. 2.09-2.35 7. 10.4-12.5 8. 0.52-0.90 (Pan)

0.5-0.6 (green) 0.6-0.7 (red) 0.7-0.8 (NIR) 0.8-1.1 (NIR)

Spatial Resolution (meter)

30 x 30 120 x 120 (TIR)

15 x 15 (Pan) 30 x 30 60 x 60 (TIR)

79 x 79

Temporal Resolution (revisit in days)

16 16 18

Spatial coverage (km)

185 x 185 183 x 170 185 x 185

Altitude (km) 705 705 915 (Landsat 1,2,3)

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Planimetric data – roads, buildings, driveways Spatial Resolution

80 meter MSS w/ planimetric overlay Spatial Resolution

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30 meter TM w/ planimetric overlay Spatial Resolution

10 meter SPOT w/ planimetric overlay Spatial Resolution

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1 meter DOQ w/ planimetric overlay Spatial Resolution

Sub-meter data w/ planimetric overlay Spatial Resolution

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Looking More Closely at Resolution

Looking More Closely at Resolution

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Landsat MSS Satellite 80 Meter Resolution Grid Cell

Looking More Closely at Resolution

Landsat TM Satellite 30 Meter Resolution Grid Cell

Looking More Closely at Resolution

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SPOT Satellite 10 Meter Resolution Grid Cell

Looking More Closely at Resolution

IKONOS Satellite 4 Meter Resolution Grid Cell

Looking More Closely at Resolution

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IKONOS Satellite 1 Meter Resolution Grid Cell

Looking More Closely at Resolution

Landsat 7 185 by 170 km

30-m multispectral

Indian Remote Sensing

145 by 145 km 25-m multispectral

SPOT 60 by 60 km

20-m multispectral

QuickBird 2 16 by 16 km

2.5-m multispectral

IKONOS 11 by 11 km

4-m multispectral

Selected Satellite Footprints

OrbView 3 8 by 8 km

4-m multispectral 1-m panchromatic10

10 100

10 100

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Resolutions of Remote Sensing

1. Spatial (what area and how detailed)

2. Spectral (what colors – bands)

3. Temporal (time of day/season/year)

4. Radiometric (color depth)

The best spatial resolution?

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1. Spatial (what area and how detailed)

2. Spectral (what colors – bands)

3. Temporal (time of day/season/year)

4. Radiometric (color depth)

Resolutions of Remote Sensing

Spectral Response Curve

http://www.cas.sc.edu/geog/rslab/Rscc/mod1/emrpaths.gif

EMR patterns are recorded by sensors with separated spectral bands.

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Electromagnetic Radiation (EMR)

Spectral Response Curve

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The spectral reflectance curves, or spectral signatures, of different types of ground targets provide the knowledge base for information extraction.

Spectral Response Curve

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Spectral Response Curve

Spectral responses from ground tragets are recorded in separate spectral bands by sensors.

Concept of Spectral Bands

Spectral Resolution • Number of spectral bands (red, green, blue, NIR,

Mid-IR, thermal, etc.) • Width of each band • Certain spectral bands (or combinations) are

good for identifying specific ground features

• Panchromatic – 1 band (B&W) • Color – 3 bands (RGB) • Multispectral – 4+ bands (e.g. RGBNIR) • Hyperspectral – hundreds of bands

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Comparison of Landsat Sensors

Thematic Mapper (TM) Landsat 4 and 5

Enhanced Thematic Mapper Plus (ETM+)

Landsat 7

Multispectral Scanner (MSS)

Landsat 1-5 Spectral Resolution (µm)

1. 0.45-0.52 (B) 2. 0.52-0.60 (G) 3. 0.63-0.69 (R) 4. 0.76-0.90 (NIR) 5. 1.55-1.75 (MIR) 6. 2.08-2.35 (MIR) 7. 10.4-12.5 (TIR)

1. 0.45-0.52 2. 0.53-0.61 3. 0.63-0.69 4. 0.78-0.90 5. 1.55-1.75 6. 2.09-2.35 7. 10.4-12.5 8. 0.52-0.90 (Pan)

0.5-0.6 (green) 0.6-0.7 (red) 0.7-0.8 (NIR) 0.8-1.1 (NIR)

Spatial Resolution (meter)

30 x 30 120 x 120 (TIR)

15 x 15 (Pan) 30 x 30 60 x 60 (TIR)

79 x 79

Temporal Resolution (revisit in days)

16 16 18

Spatial coverage (km)

185 x 185 183 x 170 185 x 185

Altitude (km) 705 705 915 (Landsat 1,2,3)

QuickBird Satellite True-color and

Pseudo-color Images 2.5-m Spatial Resolution

Concept of Multispectral And Pseudo-color Image

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Landsat-7 ETM+ Data (30 m), Bands 4, 3, 2 in RGB

Landsat-7 Panchromatic Data (15 m) Landsat-7 ETM+ Data (30 m), Bands 3, 2, 1 in RGB

Landsat-7 ETM+ Data (30 m), Bands 4, 5, 3 in RGB

Spectral Response Curve April and May Spectra for P. australis

and S. patens

0

0.1

0.2

0.3

0.4

0.5

0.6

350 450 550 650 750 850 950

Wavelength (nm)

R ef

le ct

an ce

(% )

April P. australis May P. australis April S. patens May S. patens

Blue Green Red NIR

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Spectral Response Curves April and May Spectra for P. australis

and S. patens

0

0.1

0.2

0.3

0.4

0.5

0.6

350 450 550 650 750 850 950

Wavelength (nm)

R ef

le ct

an ce

(% )

April P. australis May P. australis April S. patens May S. patens

Blue Green Red NIR Mid-IRViolet

Airborne Terrestrial Applications Sensor (ATLAS)

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Landsat-7 ETM+

1 - 4 5 7 6band #

ATLAS

1 - 6 7 8 10 11 12 13 14 15band #

wavelength (µm)

8.0 9.0 11.010.0 12.00.0 1.0 2.0

Band 1: 0.45-0.52µm (blue). Provide increased penetration of water bodies, as well as supporting analysis of land use, soil, and vegetation characteristics.

Band 2: 0.52-0.60µm (green). This band spans the region between the blue and red chlorophyll absorption bands and therefore corresponds to the green reflectance of healthy vegetation.

Band 3: 0.63-0.69µm (red). This is the red chlorophyll absorption band of healthy green vegetation and represents one of the most important bands for vegetation discrimination.

Spectral Cover of Landsat Sensors

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• Band 4: 0.76-0.90µm (reflective infrared). This band is responsive to the amount of vegetation biomass present in the scene. It is useful for crop identification and emphasizes soil-crop and land-water contrasts.

• Band 5: 1.55-1.75µm (mid-infrared) This band is sensitive to the amount of moisture in plants and therefore useful in crop draught and in plant vigor studies.

• Band 6: 2.08-2.35µm (thermal infrared) This band measures the amount of infrared radiant flux emitted from surface.

• Band 7: 2.08-2.35µm (mid-infrared) This is an important band for the discrimination of geologic rock formation. It is effective in identifying zones of hydrothermal alteration in rocks.

Spectral Cover of Landsat Sensors

Hyperspectral Data

Example:

Hyperion hyperspectral sensor is capable of resolving 220 spectral bands at 10 nm interval (from 0.4 to 2.5 µm) with a 30 meter spatial resolution.

The shown image, acquired April 6, 2004, is displayed as

-- 640.50 µm in Red color -- 548.92 µm in Green color -- 457.34 µm in Blue color

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Hyperspectral Data

AVIRIS Data Ninigret Pond Rhode Island

True Color vs.

Pseudo Color

Thermal Band (Landsat TM band 6)

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1. Spatial (what area and how detailed)

2. Spectral (what colors – bands)

3. Temporal (time of day/season/year)

4. Radiometric (color depth)

Resolutions of Remote Sensing

Temporal Considerations

Time of day/season image acquisition

• Leaf on/leaf off • Tidal stage • Seasonal differences • Shadows • Phenological differences • Relationship to field sampling

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Spring - bands 4,5,3

• Spatial • Spectral • Temporal

(seasonal)

• Radiometric

Seasonal Considerations

Summer - bands 4,5,3

• Spatial • Spectral • Temporal

(seasonal)

• Radiometric

Seasonal Considerations

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Seasonal Leaf-on vs. Leaf-off

Seasonal Leaf-on vs. Leaf-off

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Mt. Kilimanjaro

(5,895m)

Mt. Meru (4,566m)

Forest Cover 1987

Mt. Meru (4,566m)

Mt. Kilimanjaro

(5,895m)

Forest Cover 2000

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Landsat June 21, 2000

Landsat June 14, 2003

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How much has changed? How severe was the damage?

What will be the ecosystem impacts? ……

Repeat Coverage Considerations

• Revisit period for satellites – how often can you make a measurement for the same area – Landsat – 16 days (continuous collection) – Quickbird – varies (point-and-shoot) – MODIS – daily (continuous collection)

• Airborne images – collected as needed

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Comparison of Landsat Sensors

Thematic Mapper (TM) Landsat 4 and 5

Enhanced Thematic Mapper Plus (ETM+)

Landsat 7

Multispectral Scanner (MSS)

Landsat 1-5 Spectral Resolution (µm)

1. 0.45-0.52 (B) 2. 0.52-0.60 (G) 3. 0.63-0.69 (R) 4. 0.76-0.90 (NIR) 5. 1.55-1.75 (MIR) 6. 2.08-2.35 (MIR) 7. 10.4-12.5 (TIR)

1. 0.45-0.52 2. 0.53-0.61 3. 0.63-0.69 4. 0.78-0.90 5. 1.55-1.75 6. 2.09-2.35 7. 10.4-12.5 8. 0.52-0.90 (Pan)

0.5-0.6 (green) 0.6-0.7 (red) 0.7-0.8 (NIR) 0.8-1.1 (NIR)

Spatial Resolution (meter)

30 x 30 120 x 120 (TIR)

15 x 15 (Pan) 30 x 30 60 x 60 (TIR)

79 x 79

Temporal Resolution (revisit in days)

16 16 18

Spatial coverage (km)

185 x 185 183 x 170 185 x 185

Altitude (km) 705 705 915 (Landsat 1,2,3)

Resolutions of Remote Sensing

1. Spatial (what area and how detailed)

2. Spectral (what colors – bands)

3. Temporal (time of day/season/year)

4. Radiometric (color depth)

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Radiometric Resolution Every time an image is acquired by a sensor, its sensitivity to the magnitude of the electromagnetic energy determines the radiometric resolution.

The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy.

Imagery data are represented by positive digital numbers which vary from 0 to a selected power of 2. This range corresponds to the number of bits used for coding numbers in binary format. Each bit records an exponent of power 2.

The maximum number of brightness levels available depends on the number of bits used in representing the energy recorded. Thus, if a sensor used 8 bits to record the data, there would be 28=256 digital values available, ranging from 0 to 255.

Maximum Values

204 8

1024512256128643216842

Number of bits1110987654321

8 bits 11 bits

Data volume will increase as the radiometric resolution increases?