Data in GIS: Remote Sensing Prof' Carolyn Merry Dept' of Civil

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Data in GISRemote Sensing Prof. Carolyn
MerryDept. of Civil Environmental Engineering
Geodetic ScienceCollege of Engineeringmerry.
1_at_osu.edu
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Definition of Remote Sensing

• "Remote sensing is the practice of deriving
  information about the earth's land and water
  surfaces using images acquired from an overhead
  perspective, using electromagnetic radiation in
  one or more regions of the electromagnetic
  spectrum, reflected or emitted from the earths
  surface. (Campbell, 1996)

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Platforms Used toAcquire Remote Sensing Data

• Aircraft
• Low, medium high altitude
• Higher level of spatial detail
• Satellite
• Polar-orbiting, sun-synchronous
• 800-900 km altitude, 90-100 minutes/orbit
• Geo-synchronous
• 35,900 km altitude, 24 hrs/orbit
• stationary relative to Earth

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Electromagnetic Spectrum

• Remote sensing images are taken within specific
  spectral regions

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TM 4 near IR
TM 2 green
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SPOT band 3 near IR
SPOT band 1 green
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Spectral Reflectance Curve

• Distinctive spectral response patterns for earth
  surface features

High
Vegetation
Soil
Spectral Reflectance
Water
Low
Blue Green Red Near IR
Mid IR
Spectral Region
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Electromagnetic Radiation

• Passive remote sensing
• reflected radiation UV, visible, NIR, MIR
• emitted radiation thermal IR
• depends on external energy source, Sun
• Active remote sensing
• energy transmitted from remote sensing platform,
  use reflected energy to form an image
• manmade radiation (microwave band of wavelengths
  imaging radars)
• operate at night during cloudy weather

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What is a digital image?
Source NASA Observatorium
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Remote Sensing Digital Images

• Scanned aerial photographs
• Digital cameras
• Video images
• Satellite images
• Radar images

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Advantages of Remote Sensing Data

• Remote sensing data may be more current
• Map a large variety of themes from one image
• Users can interpret remote sensing imagery
• Images cover large areas in one snapshot

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Image Resolution

• Spatial
• Refers to pixel size of image
• Images with small ground pixel sizes are of high
  spatial resolution
• Landsat-7 30 m vs. Ikonos 4 m

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OSU Campus
Landsat-7 ETM 30-m
Ikonos 4-m
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Image Resolution (contd)

• Spectral resolution
• Band width recorded by the remote sensing image
• Narrower the wavelength band, the better the
  spectral resolution

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Landsat Multispectral Scanner (MSS)

• 79-m (82-m) resolution for 4 bands
• Band 1 - Green 0.5-0.6 mm
• Band 2 - Red 0.6-0.7 mm
• Band 3 - Near infrared 0.7-0.8 mm
• Band 4 - Near infrared 0.8-1.1 mm

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Spectral Band Coverage for the Landsat Thematic
Mapper 30-m resolution
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Image Resolution (contd)

• Temporal resolution
• How frequently the image is acquired
• AVHRR daily coverage vs. Landsat TM every 16 days
• Radiometric resolution
• Number of reflectance values that can be recorded
• AVHRR 210 (1024 gray levels) data vs. Landsat TM
  28 (256 gray levels) data

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Historical Archive
Landsat 5, 1984
Landsat 5, 1989
Landsat 5, 1994
Landsat 7, 1999
DISP, 1962
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Satellite Imagery
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Newest Satellite Imagery

• Landsat-7 ETM (April, 99)
• 7 multispectral bands (30-m resolution, 60-m
  thermal band)
• 15-m panchromatic band
• IKONOS-1 (September, 99)
• 1-m pan, 4-m multispectral (4 bands)
• Quickbird (October, 01)
• 0.6 m pan, 2.5-m multispectral (4 bands)

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Landsat-7 coverage over Ohio
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Landsat-7 ETM 30-m XS
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Landsat-7 ETM 15-m pan
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DLG files
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ETM
Ikonos
DEM
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Cedar Point, Ohio
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IKONOS 4-m Olympic Park Sydney, Australia
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Statue of Liberty 60-cm natural
color QuickBird 2 Aug 02
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How to Use Remote Sensing Data

• Process satellite imagery using image processing
  methods
• geometric corrections are made
• classification imported into GIS
• register to GIS coordinate system
• Enter as raw image data
• use as backdrop for vector data

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Spectral pattern recognition
Source Canadian Center for Remote Sensing
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Geometric registration process
Image-to-map registration
Source Canadian Center for Remote Sensing
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Using Remote Sensing Data (contd)

• Manual interpretation of aerial photographs
• Interpret the imagery identify features draw
  boundaries
• Produce a map or set of maps
• Need to correct for geometric errors
• Boundaries digitized imported into GIS

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Typical Data Sets DerivedFrom Remote Sensing Data

• Land use/land cover maps, particularly changes in
  land use/land cover
• Elevation
• Temperature
• Biomass estimates
• Vegetation types

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Digitize Aerial Photoswith Stereoplotters

• Aerial photos registered to selected reference
  coordinate system vertical datum
• Orient stereoplotter to ground control points
  (GCPs) before digitizing
• Digitize planimetric features when viewing the
  3-D stereomodel
• DEM read automatically from created 3-D
  stereomodel

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Why is Elevation So Important?

• Elevation contours digitize critical points
  along contours
• Software used to derive triangular irregular
  network (TIN)
• TIN used to derive point elevations, profiles,
  cross-sections, slopes, aspects, contours at
  any interval

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Using Topographic Data

• Calculate shortest path or most navigable path
  over a mountain range to construct road, route or
  transmission line
• Assess visibility from various lookout points or
  along roads
• Simulate travel through landscape
• Create aspect slope layers generate shaded
  relief images
• Provide data layer to use with satellite image
  classification GIS modeling

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Pan image laser elevations plotted as intensity
Courtesy of EarthData Technologies
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Digital Orthophotographs

• Planimetrically corrected aerial photograph
  (effects of relief tilt displacements are
  removed)
• USGS - quadrangle-based with 4 images per
  7.5-minute quad
• Projected into UTM system - 1 m pixel size - 28
  bit data

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On-line tutorials in remote sensing

• Fundamentals of remote sensing - CCRS
• http//www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/f
  undam/fundam_e.html
• NASA remote sensing tutorial
• http//rst.gsfc.nasa.gov/start.html
• Remote sensing core curriculum
• http//research.umbc.edu/tbenja1/umbc7/

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Uses of Remote Sensing (from Cracknell Hayes,
1991)