Steve Miller 23 May 2014 Approach Examine anthropogenic lights cities near sealevel and at higher altitude Select two adjacent orbits passes which provide i an eastern view ii a western view ID: 249683
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Slide1
DNB Terrain Correction Performance
Steve Miller
23 May 2014Slide2
Approach
Examine anthropogenic lights (cities) near sea-level and at higher altitude.
Select two adjacent orbits passes which provide i) an eastern view, ii) a western view.
To maximize possible parallax displacements, select locations near scan edge.
Cloud-free views to minimize ambiguity due to obscuration and additional parallax effects.
Compare east/west passes at each location for the original (non-terrain-corrected) and new (terrain-corrected)
geolocation
data.
A consistent terrain correction will result in minimal feature shift between the eastern and western views.
[Note: please run this
powerpoint
in slide-show mode in order to toggle imagery and compare the east/west views]Slide3
Selected Domain
of Analysis
Baku, Azerbaijan (40.4N,49.9E,-28m)
Isfahan, Iran
(32.63N,51.65E, 1.59 km)Slide4
East and West Suomi
NPP Passes
Eastern Scan
Edge
Western Scan
Edge
2143 UTC 2324 UTC
Baku
Isfahan
This pairing provides a nearly optimal comparison between a low and high altitude light source at opposite viewing directions…Slide5
Baku (40.4˚N, 49.9˚E,
-0.28 km
)
2143 UTC
2324 UTC
No Correction
Terrain Correction
Baku is close to sea level: parallax
displacement effects
are minimal
Terrain
correction has little
impact
Some notable shifts to lights West/Northwest are evident of Baku, from higher elevation towns nestled in the Greater Caucasus RangeSlide6
Isfahan (
32
.63˚N, 51.65˚E
,
1.59
km)At 5,217 feet (1.59 km) Isfahan parallax effects are substantial
Terrain correction has significant impact (note dramatic shift of Isfahan in the left-panel, in contrast to relative stability in the right panel.
Note of caution
: clouds under-lit by cities will cause apparent shifts in city
light locations, since the terrain correction is done with respect to the terrain elevation,
not with respect to the cloud altitudes!!!
No Correction
Terrain Correction
2143 UTC
2324 UTCSlide7
Summary
The ~sea level site exhibits little shift for both terrain-corrected and non terrain-corrected
geolocation
, as expected.
The high-elevation site shows dramatic improvements in stability of signal for the terrain-corrected
geolocation.
Other examples (W. Straka, CIMSS) have shown the intra-band consistency of terrain-corrected geolocation by comparing DNB with M10 and M13 imagery of fires.There is some evidence of changes in lights between the two passes, particularly for point sources—it has yet to be determined whether these changes are the result of lights physically changing (turn-on/off), artifacts of image registration, or (more likely) a combination of both.
Preliminary results are encouraging—should allow for improved multi-spectral applications involving the DNB, particularly with respect to surface lights at-elevation.