Fundamentals of remote sensing lecture 2

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Fundamentals of remote sensing lecture - 2

• Dr Daniel Donoghue

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Obtaining global coverage from space

• Geosynchronous or geostationary
• Located directly above equator 36,000 km from
  Earth
• Orbit at the same rate as Earth rotation
• Used for meteorology

• Polar or near polar
• Approx 90 min orbital period
• Operate close to the Earth from 100 800 km
• Near Polar orbits can be sun synchronous the
  orbit shifts by approx 1 degree per day

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Typical Earth Observation System

• http//science.nasa.gov/realtime/jtrack/Spacecraft
  .html
• Allows measurements to be compared
• Revisit period is typically 16-18 days
• Off-NADIR viewing can reduce revisit period to 4
  days or less

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Global Positioning System

• 24 satellites in Circular orbits 20,200 km above
  Earth
• 12 hour period
• Min of 6 visible at any one time
• Operated by US Department of Defence
• Transmit accurate position and time signal
• SPS 100 m horizontal
• PPS 6 m or less
• Selective availability set to zero 1 May 2000

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SRTM coverage from Low Earth Equitoral orbit
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Near-Polar Earth Observation Sensors

• Sensor Bands
• Landsat MSS 4
• Landsat TM 7
• Landsat ETM 8
• SPOT XS 4

• Sensor Bands
• AVHRR
• MODIS
• MERIS
• SPOT Vegetation

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• Geostationary

• Near-Polar
• Landsat 185 km2

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ESA - ENVISAT
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Sensor types

• Scanning mirror

• Array or pushbroom

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Frame system
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Application areas

• Global Topography
• Global climate monitoring
• Carbon balance
• Sea Ice change
• Sea surface temperature

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Shuttle Radar Topography Mission

• Global coverage at 3 arc seconds (90 m)
• USA coverage at 1 arc second (30 m)
• Available freely to researchers

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SRTM Mission using RADAR Interferometry
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1km and SRTM 30 m data
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Value of remote sensing

• Land use mapping
• Land use change assessment
• Fire and burn assessment
• NPP and forest quality assessment
• Parameterising carbon models

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Land use change in Indonesia
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Summary 1

• Orbits determine scale and coverage of satellite
  data
• Spatial
• Temporal
• Sensor characteristics determine the science
  application
• Spectal
• Radiometric
• Acquisition, relay and archiving

• Contrast geostationary and near-polar orbital
  systems e.g. Meteosat and Landsat
• / - Trade off
• High rate of repeat coverage -gt low spatial
  resolution
• Sun synchronous system has low repeat rate but
  yields good radiometric data
• Low Earth orbit non sun synchronous can acquire
  high spatial resolution but yields poor
  radiometric data
• Data availability depends on ground segment and
  archiving

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Summary 2

• Topography
• Carbon
• Sea Ice
• Sea surface temperature

• Difficult to measure at global scale with
  accuracy
• SRTM coverage is determined by Shuttle orbit
  pattern
• Science requirements are often both Global and
  regional e.g. vegetation dynamics (greening up)
  or El Nino events need a global view while
  tropical deforestation or iceberg calving needs a
  detailed view

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Water resources
Recognizing the utility of satellite data for
water resource management elsewhere and the
urgent need for action in Africa expressed at the
WSSD, the European Space Agency in the context of
the Committee of Earth Observation Satellites
(CEOS) WSSD follow-on programme, launched in 2002
the TIGER initiative aimed at "assisting African
countries to overcome problems faced in the
collection, analysis and dissemination of water
related geo-information by exploiting the
advantages of Earth Observation (EO)
technology". The achievement of this objective
requires a long-term strategy pursuing three main
categories of results
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TIGER - Aims

• Support improved governance and decision-making
  develop, implement and assess a cost-effective
  sustainable model to improve decision-making and
  governance (at regional, national and local
  scales) by using space-based information to
  provide accurate and timely geo-information for
  the integrated water resource management
  process.Contributing to enhance institutional,
  human and technical capacity support the
  consolidation of a critical mass of technical
  centres in Africa with the skills and
  capabilities to derive and disseminate
  space-based information to water authorities at
  regional, national and local scales.
• Fostering sustainability Development of strategy
  for strengthening and sustaining EO-supported
  information and decision-support systems in the
  long term.