1. 2 part ii remote sensing using reflected visible and infrared radiation 602-marcampus closedch...

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Lecture 10

Multi-Spectral Remote SensingSystem Considerations Part I

March 25th 2009

Part II Remote Sensing using Reflected Visible and Infrared Radiation 6 02-Mar Campus Closed Ch 17.1-17.3

04-Mar 7 Surface reflectance – Land Surfaces I05-Mar Lab 2 Contrast stretching and DN to reflectance conversion in ENVI

7 09-Mar 7 extended, 8 Surface reflectance 11-Mar 8 Water Bodies Ch 19.1-19.612-Mar Lab 3 Visual Analysis and High Resolution Visual Analysis

8 16-Mar Spring Break18-Mar

9 23-Mar 9 Detection of EM Radiation by a Vis/IR Radiometer 25-Mar 10 Multispectral Remote Sensing Systems I Ch 6,2126-Mar Lab 4 Reflectance Spectra Compared to RS Images and Veg Index

10 30-Mar Multispectral Remote Sensing Systems II Ch 6,2101-Apr 11 Multispectral Remote Sensing Data Analyses I Ch 12,17.9-17.1002-Apr Lab 5 Image Classification

11 06-Apr 11 Multispectral Remote Sensing Data Analyses II08-Apr Exam 2 – will cover material presented in Lectures 7-1109-Apr Lab 6 Multi-temporal change detection

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1. Key questions for designing space borne radiometers

2. Considerations for deploying a space borne radiometer

3. Problems in imaging over wide swaths4. Summary of system tradeoffs5. Categories of satellite radiometers6. High Resolution Remote Sensing

Lecture Topics

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Radiometer – An instrument that measures radiance in a specified wavelength region

Spectroradiometer or spectrometer – An instrument that measures radiance continuously across a region of the EM spectrum or in multiple-bands across a region of the EM spectrum

Radiometers and Spectrometers

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What reflectance characteristics are you trying to measure? Spectral resolution

How precisely do you have to measure radiance? Radiometric resolution

How large are the features of interest? Spatial resolution and swath width

How frequently and when do you have to measure the features of interest? Temporal resolution

Questions to ask when designing a multi-channel spaceborne radiometer

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Spectral Resolution – the wavelength regions of and bandwidths for a radiometer

Radiometric Resolution - the sensitivity of a remote sensing detector to variations in the emitted, reflected or scattered EM energy that is being detected

Spatial Resolution - The measure of the smallest distance (linear or angular separation) between objects that can be resolved by the sensor

Temporal Resolution – the timing and frequency for collection of data by a satellite system

Resolution

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All scanning radiometers have an instantaneous field of view over which the sensor detects EM energy for a specific pixel

Spatial Resolution is determined by the Instantaneous Field of View- IFOV

IFOV (in degrees, )

Radius of circle within IFOV, r = H tan /2

For very small IFOV, e.g., <<< 0.01º, r = H /2, where is in radians

H

Sensor

r

Fig. 5

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If you are imaging over a very wide swath, then H will increase as you scan away from nadir, meaning the size of the IFOV on the ground will increase

Changes in IFOV

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Temporal resolution has three important components –

a. How frequently you have to observe a specific area on the earth’s surface to capture variations over time of the phenomena being observed

b. When during the year the phenomena you are monitoring occurs

c. The diurnal (e.g., 24 hour) variations in the signature being observed

1. Variations in solar illumination2. Variations in the occurrence of the phenomena3. Variations in characteristics of the atmosphere

Temporal Resolution

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How large of an area does the remote sensing system have to capture in order to collect data about the features or processes of interest?

Swath widths of satellite remote sensing systems range between 7 and 2,500 kilometers

Swath width + the orbital path of the satellite determine temporal resolution

Swath Width

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Lecture Topics

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1.What is the size of the area or patch being detected by the satellite radiometer?

2.How frequently can a satellite view the same piece of ground on the earth’s surface?

3.How large an area is imaged by the sensor?

4.How much data are being recorded by the radiometer and how do we retrieve these data?

5.How do variations in surface and atmospheric conditions affect the data quality?

Considerations for deployment of a satellite radiometer

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1. What is the size of the area or patch being detected by the satellite radiometer?

Determined by A. The IFOV of the sensorB. The height of the satellite platformC. The scanning angles of the radiometer


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3.How large an area is imaged by the sensor?4.How much data are being recorded by the

radiometer and how do we retrieve these data?5.How do variations in surface and atmospheric

conditions affect the data quality?


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1. The orbital time of the satellite2. The width of the area being imaged by a

satellite when it passes over the earth

Controls on Frequency of Coverage by a Satellite (temporal resolution)

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A satellite in low earth orbit (~800 km) takes about 90 minutes to complete a single passage from equator to equator

Fig. 6

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H = 800 km

Satellite

Swath width = 2460 km

Viewing angle of 57° off nadir to image swath

Fig. 7

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H = 800 km

Satellite

Swath width = 172 km

Viewing angle of 6.1°off nadir to image swath

Fig. 8

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1. Ground receiving station within direct view of the satellite (to acquire global coverage requires a large number of stations)

2. On-board data recorders (requires reliable, large volume recorders)

3. Using data relay satellites – e.g., the TDRSS - Tracking and Data Relay Satellite System

Approaches to Recover Data from Satellite Remote Sensing Systems

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Wide Swath / Low Resolution

Narrow Swath/High Resolution

Image Size 2460 by 2460 km 172 by 172 km

Ground area size (resolution or pixel size)

1 by 1 km 0.05 by 0.05 km(50 by 50 m)

Number of radiometer channels 4 4

Images per orbit 16 228.8

Pixels per image per channel 6 million 11.8 million

Pixels per orbit per channel 96 million 2.7 billion

Pixels per orbit for all channels 384 million 10.8 billion

High resolution, wide swath – pixels per orbit for all channels

155 billion

Data per day 2.5 trillion

Data per month 743 trillion

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In most regions with significant vegetation, there is a diurnal variation in atmospheric moisture and cloud cover that is driven by evapo-transpiration by plants

In many areas, the resulting cloud formation hinders viewing of the earth’s surfaces over land areas by the early afternoon

Because of this, many sensors schedule fly-over times between 10 am and noon

Atmospheric Conditions

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Lecture Topics

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1. The size of your ground footprint gets bigger as the angle off nadir increases

2. Atmospheric effects increase3. The bidirectional reflectance at the surface

often changes, e.g., the emittance from the surface for the same surface cover type changes

Problems with imaging over wide swaths

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Relative size of ground area as a function of look direction

0

3

6

9

12

15

0 15 30 45 60

Look angle off nadir

Rel

ativ

e g

rou

nd

are

a si

zeFig. 10

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1. The size of your ground footprint gets bigger as the angle off nadir increases

2. Atmospheric effects increase3. The bidirectional reflectance at the surface

often changes, e.g., the emittance from the surface for the same surface cover type changes

Problems with imaging over wide swaths

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Effects of atmosphere on incoming/outgoing EM energy is proportional to distance traveled through the atmosphere

As incidence angle increases, atmospheric effects (scattering, absorption, attenuation) increase

Using wide swath width increases the requirements for atmospheric correction of the data

Atmospheric effects

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Further information on this slide can be viewed athttp://snrs.unl.edu/agmet/908/brdf_definition.htm

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Lecture Topics

Summary of System Tradeoffs (+) advantage, (-) disadvantage

Narrow-Swath, Higher Resolution Wide-Swath, Lower Resolution

(-) Coverage only every 15 to 20 days (less if cloud cover exists)

(+) Daily coverage of area

(+) High resolution imagery (-) Low resolution imagery

(-) Higher data volumes requires on-board recording or direct transmission

(+) Lower data volumes result in less stringent recording/direct transmission requirements

(+) Narrow viewing angle results in lower atmospheric / bi-directional scattering effects, and consistent across-swath resolution

(-) Wider viewing angle results in greater atmospheric / bi-directional scattering effects, and variable across-swath resolution

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Lecture Topics

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1. Wide swath, low resolution• 1000-2600 km swath, 500 to 1100 m

2. Moderate swath, moderate resolution• 100 to 200 km swath, 10 to 50 m resolution

3. Narrow swath, fine resolution• 5 to 15 km swath, 1 to 4 m resolution

Categories of satellite radiometers

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Lecture Topics

Description of commercial high resolution remote sensing IkonosOrbimageQuickbirdGeoeye

Applications of High resolution dataNational SecurityPreparation to respond to eventsMonitor activitiesMonitor Transportation NetworksUrban PlanningTax assessments

High Resolution remote sensing

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Along-track, or Pushbroom, Multispectral System Operation

IkonosSensor Overview

On September 24, 1999, an Athena II rocket carried the 1600-pound IKONOS satellite into a 684-kilometer (423-mile) polar orbit. IKONOS is the world’s first high-resolution commercial remote sensing satellite with a ground

resolution of .82-meters. IKONOS is derived from the Greek word for "image." The IKONOS satellite is the world's first commercial satellite to collect black-and-white images with 1-meter resolution and multispectral imagery with 4-meter resolution.

http://www.geoeye.com/corporate/constellation.htm

IkonosSensor CharacteristicsIt orbits the Earth every 98 minutes at an altitude of approximately 680 kilometers or 423 miles. IKONOS was launched into a sun-synchronous orbit, passing a given longitude at about the same local time (10:30 A.M.) daily. IKONOS can produce 1-meter imagery of the same geography every 3 days.

IkonosSpectral Range1-meter black-and-white (panchromatic)450 - 900 nm. 4-meter multispectral Blue: 450 - 520 nmGreen: 510 - 600 nmRed: 630 - 700 nmNear IR: 760 - 850 nmProductsStandard products include 1-meter black-and-white, 4-meter multispectral (all bands), 1-meter color (true color, false color, or 4-band), and a 1-meter and 4-meter data bundle.IKONOS image data is available in easy to use 8-bit or full dynamic range 11-bit format.

IkonosLaunch Date 24 September 1999Vandenberg Air Force Base, California, USAOperational Life Over 7 yearsOrbit 98.1 degree, sun synchronousSpeed on Orbit 7.5 kilometers per secondSpeed Over the Ground 6.8 kilometers per secondNumber of Revolutions Around the Earth 14.7 every 24 hoursOrbit Time Around the Earth 98 minutesAltitude681 kilometersResolution Nadir:0.82 meters panchromatic3.2 meters multispectral26° Off-Nadir1.0 meter panchromatic4.0 meters multispectralImage Swath 11.3 kilometers at nadir 13.8 kilometers at 26° off-nadirEquator Crossing Time Nominally 10:30 a.m. solar timeRevisit Time Approximately 3 days at 40° latitudeDynamic Range11-bits per pixelImage Bands Panchromatic, blue, green, red, near IR

Ikonos Standard IKONOS Stereo products include:Stereo 1-meter Black-and-WhiteStereo 1-meter Color Stereo imagery is available for IKONOS 1-meter Reference and Precision products. Imagery pairs are delivered with a Rational Polynomial Coefficient (RPC) camera model file. The RPC file enables photogrammetric processing, creation of digital terrain models and 3-dimensional measurement with popular software packages.

Ikonos

IkonosItaipu Dam

Ikonos

Ikonos High-resolution data products and services to help organizations:

• Monitor, plan and prepare for disasters and emergencies• Prepare response efforts for natural, terrorist and unintentional events• Analyze information and provide relevance• Provide for preventative action and timely response resulting in reduced consequences• Evaluate critical infrastructures• Monitor border and transportation activities• Actively support first responders, related military organizations, citizens and non-government organizations• Support efficiency and options for recovery

Orbview-3On June 26, 2003, a Pegasus XL successfully launched OrbView-3 into a 470-kilometer (292-mile) sun-synchronous orbit. The satellite is capable of providing one-meter resolution panchromatic and four-meter resolution multispectral imagery.

Orbview-3The Pegasus's three Orion solid motors were originally developed for the cancelled Midgetman (a small ICBM to be launched from a trailer) by Hercules Aerospace (now Alliant Techsystems). For Pegasus use, wing and tail assemblies and a payload fairing were developed. Most of the Pegasus was designed by a design team led by Dr. Antonio Elias. The wing was designed by Burt Rutan.· Mass: 18,500 kg (Pegasus), 23,130 kg (Pegasus XL) · Length: 16.9 m (Pegasus), 17.6 m (Pegasus XL) · Diameter: 1.27 m · Wing span: 6.7 m Payload: 443 kg (1.18 m diameter, 2.13 m length)

Orbview-3Facts at a Glance Spatial Resolution 1 meter Panchromatic4 meters Multispectral Spectral Range:Panchromatic 450-900 nm Multispectral Blue: 450-520 nmGreen: 520-600 nmRed: 625-695 nmNear IR: 760-900 nm Swath Width 8 km Off-Nadir Imaging Up to 50 degrees Dynamic Range 11 bits per pixel Mission Life Expected > 7 years Revisit Time Less than 3 days Orbital Altitude 470 km Modal Crossing 10:30 A.M.

Orbview-3IMAGERY APPLICATIONSOrbView-3 is used for a wide variety of commercial and government applications. These applications include environmental impact assessments for engineering companies; infrastructure planning for utilities and telecommunications; urban planning in city and county governments; crop health assessment; exploration for oil, gas and mineral companies; habitat monitoring for environmental agencies; and surveillance and mission planning for national security agencies.

Quickbird

http://www.digitalglobe.com/

Quickbird

Was Highest resolution sensor available commercially 60-cm (2-ft) panchromatic at nadir2.4-m (8-ft) multispectral at nadirStable platform for precise location measurement3-axis stabilized, star tracker/IRU/reaction wheels, GPSFastest large area collection 16.5-km width imaging swath128 Gbits on-board image storage capacityOff-axis unobscured design of QuickBird's telescope Large field-of-view High contrast (MTF) High signal to noise ratio 11 bit dynamic range Quantization 11 bits

QuickbirdDepending upon orbital altitude, ground sample distances between 0.5 and 1.5 meters panchromatic and 2 to 8 meters multispectral can be achieved.

The pushbroom camera, pointed and oriented by the spacecraft, is capable of imaging a strip of the Earth's surface between 14 and 34 km wide (specifications). The multispectral bands mimic the first four bands of the Landsat system (the visible NIR regions of the electromagnetic spectrum).

QuickbirdLaunch Date October 18, 2001

Launch Vehicle Boeing Delta II

Launch Location Vandenberg Air Force Base, California, USA

Orbit Altitude 450 Km

Orbit Inclination 97.2º, sun-synchronous

Speed 7.1 Km/second - 25,560 Km/hour

Equator Crossing Time 10:30 a.m. (descending node)

Orbit Time 93.5 minutes

Revisit Time 1-3.5 days depending on Latitude (30º off-nadir)

Swath Width 16.5 Km x 16.5 Km at nadir

Metric Accuracy 23-meter horizontal (CE90%)

Digitization 11 bits

Resolution Pan: 61 cm (nadir) to 72 cm (25º off-nadir)

MS: 2.44 m (nadir) to 2.88 m (25º off-nadir)

Image Bands Pan: 450 - 900 nm

Blue: 450 - 520 nm Green: 520 - 600 nm Red: 630 - 690 nm Near IR 760 - 900 nm

Quickbird

Geoeye-1GeoEye again made history with the Sept. 6, 2008 launch of GeoEye-1—the world's highest resolution commercial earth-imaging satellite.

GeoEye-1 is equipped with the most sophisticated technology ever used in a commercial satellite system. It offers unprecedented spatial resolution by simultaneously acquiring 0.41-meter panchromatic and 1.65-meter multispectral imagery. The detail and geospatial accuracy of GeoEye-1 imagery further expands applications for satellite imagery in every commercial and government market sector.

A polar orbiting satellite, GeoEye-1 will make 12 to 13 orbits per day flying at an altitude of 684 kilometers or 425 miles with an orbital velocity of about 7.5 km/sec or 45,000 mi/hr.

Geoeye-1Spatial Range: 0.41 m – 1.64 m

Spectral Range:Panchromatic 450-900 nm

Spectral Range Multispectral

Blue: 450-520 nmGreen: 520-600 nmRed: 625-695 nmNear IR: 760-900 nm

Swath Width 15.2 km

Off-Nadir Imaging Up to 60 degrees

Dynamic Range 11 bits per pixel

Mission Life Expected > 10 years

Revisit Time Less than 3 days

Orbital Altitude 684 km

Modal Crossing 10:30 A.M.

Geoeye-1GEOEYE-1 TECHNICAL INFORMATION

Launch Vehicle Delta II

Satellite Weight 1955 kg / 4310 lbs

Satellite Storage and Downlink

1 Terabit recorder; X-band downlink (at 740 mb/sec or 150 mb/sec)

Operational Life Fully redundant 7+ year design life; fuel for 15 years

Satellite Modes of Operation

• Store and forward• Real-time image and downlink• Direct uplink with real-time downlink

Orbital Altitude 684 kilometers / 425 miles

Orbital Velocity About 7.5 km/sec or 45,000 mi/hr

Inclination/Equator Crossing Time 98 degrees / 10:30am

Orbit type/period Sun-synchronous / 98 minutes

1 meter 0.41 meter or 1.34 ft

Geoeye-1

Part II Remote Sensing using Reflected Visible and Infrared Radiation 6 02-Mar Campus Closed Ch 17.1-17.3

04-Mar 7 Surface reflectance – Land Surfaces I05-Mar Lab 2 Contrast stretching and DN to reflectance conversion in ENVI

7 09-Mar 7 extended, 8 Surface reflectance 11-Mar 8 Water Bodies Ch 19.1-19.612-Mar Lab 3 Visual Analysis and High Resolution Visual Analysis

8 16-Mar Spring Break18-Mar

9 23-Mar 9 Detection of EM Radiation by a Vis/IR Radiometer 25-Mar 10 Multispectral Remote Sensing Systems I Ch 6,2126-Mar Lab 4 Reflectance Spectra Compared to RS Images and Veg Index

10 30-Mar Multispectral Remote Sensing Systems II Ch 6,2101-Apr 11 Multispectral Remote Sensing Data Analyses I Ch 12,17.9-17.1002-Apr Lab 5 Image Classification

11 06-Apr 11 Multispectral Remote Sensing Data Analyses II08-Apr Exam 2 – will cover material presented in Lectures 7-1109-Apr Lab 6 Multi-temporal change detection

1. 2 part ii remote sensing using reflected visible and infrared radiation 602-marcampus closedch...

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