Transcript Elvidge_EORSA_20120610

Prospects for Improved Global Mapping
of Development Using VIIRS Data
Chris Elvidge
Earth Observation Group
NOAA-NESDIS National Geophysical Data Center
325 Broadway, Boulder, Colorado 80305 USA
Tel. 1-303-497-6121
Email: [email protected]
Kimberly Baugh
Cooperative Institute for Research in Environmental Sciences
University of Colorado, Boulder, Colorado USA
June 10, 2012
Lights
At
Night!
Boats
Cities
Industrial Sites
Gas Flares
Fires
Artificial lighting is a excellent remote sensing observable!
Two Satellite Systems Collect Low
Light Imaging Data at Nights
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U.S. Air Force Defense Meteorological
Satellite Program (DMSP) Operational
Linescan System (OLS). 1972 to present.
NASA-NOAA Suomi NPP Visible Infrared
Imaging Radiometer Suite (VIIRS).
Launched October 28, 2011.
In both cases the purpose of the low light
imaging is the detection of moonlit clouds
Comparing DMSP and VIIRS
DMSP
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U.S. Air Force
Polar orbiting
07:30 and 19:30 overpasses
3000 km swath
Two spectral bands (vis and TIR)
Panchromatic low light imaging
2.7 km ground sample distance
5 km+ ground instantaneous field of
view
6 bit quantization (vis)
No inflight calibration
Saturation on bright lights in
operational collections
Direct broadcast encrypted
Archive at NGDC
Flown since 1972
May continue another three years?
VIIRS
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NASA-NOAA Joint Polar Satellite
System (JPSS)
Polar orbiting
01:30 and 13:30 overpasses
3000 km swath
22 spectral bands
DNB panchromatic low light imaging
742 meter GSD
750 meter GIFOV
14 bit quantization in DNB
In flight calibration
No saturation
Direct broadcast not encrypted
Archives at NCDC and NGDC
Launched in 2011
Series expected to continue for several
decades
DMSP Nighttime Visible
May 21, 2012 at ~19:30 local time
NGDC has produced a time series of DMSP
annual cloud-free nighttime lights
composites (1992-2011)
Shortcomings of DMSP Nighttime Lights
• Coarse spatial
resolution of the OLS
2.7 km GSD
5+ km GIFOV
• OLS lights are larger
than sources on the
ground
• “Overglow” surrounds
bright sources
• No visible band
calibration
• 6 bit quantization
• Urban centers saturate
in operational data
• No 3-5 um band for fires
Contrast enhanced to show dim lighting
VIIRS - Visible Infrared Imaging Radiometer Suite
VIIRS Nighttime Day / Night Band (DNB)
May 21, 2012 at ~ 01:30 local time
VIIRS versus DMSP May 21, 2012
VIIRS
OLS
Detection of Villages in VIIRS Nighttime Visible (DNB)
May 21, 2012 at ~ 01:30 local time
VIIRS
OLS
What Else VIIRS Has To Offer
Fire detections - discriminate
lights from combustion sources.
Cloud optical thickness and
snow cover to rate the quality of
light detections.
Aerosol daytime only
Clouds day and night
Fires day and night
Snow Cover
What needs to be developed
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Light detection algorithm
Terrain correction – DNB data are
not terrain corrected since the
primary mission is detection of
moonlit clouds.
Atmospheric correction – to estimate
upwelling radiances at the earth
surface.
The Way Forward
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Reuse portions of NGDC algorithm
base for processing DMSP nighttime
lights:
• Terrain correction
• Light detection
• Cloud-free compositing
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MODTRAN atmospheric correction
VIIRS Stray Light
The DMSP light detection algorithm operates with overlapping square tiles to
define detection thresholds and assumes that the majority of tile pixels are
background. The square tile approach does not appear to be appropriate for
VIIRS due to stray light problem.
Light Detection
Rather than square tiles – it may be more appropriate to analyze individual
scanlines – defining a background and noise level that varies from left to right.
NGDC’s plan for a 2012 global
map of development
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Initial product will be a mosaic made
with a relatively low number of
repeat observation. October 2012.
Subsequently a full year product will
be processed to characterize the
variability in lighting. March 2013.
Participate in GEO SB-04
collaborations.