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Proposed Greenland Mapping, May 2009 n Proposed LVIS Mapping in Greenland: F 11 flights, 60 ~E-W cross-country flight lines 44 km apart, and 4 ~N-S lines. F 3 week mission on DC-8, ~May F Will illuminate and sample ~5% of Greenland’s surface area. n Each line flown once, cloud issues minimized by flexible planning. n If required, additional flights to cover specifically-targeted areas. n Assumptions: F Using NASA’s DC-8 aircraft F 40,000’ altitude, 400 knot ground speed F 12 hr flights with 10 hrs for science F Thule, Sondrestrom, Keflavik base? 300 km LVIS lines, spaced 44km apart
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Mapping Greenland Using NASA’s Full-Mapping Greenland Using NASA’s Full-Waveform, Medium/High-Altitude, LVIS Waveform, Medium/High-Altitude, LVIS Lidar System: Potential 2009 Coverage Lidar System: Potential 2009 Coverage
and Expected Performanceand Expected Performance
Michelle HoftonDepartment of Geography, University of Maryland, College Park
[email protected]; 301 405 8543
J Bryan BlairNASA Goddard Space Flight Center, Greenbelt, Maryland
[email protected]; 301 614 6741
David RabineSSAI, Lanham, Maryland
NASA’s Laser Vegetation Imaging SensorNASA’s Laser Vegetation Imaging Sensor NASA’s Laser Vegetation Imaging Sensor
(LVIS) Medium/high-altitude, waveform-recording lidar. Utilizes medium-sized footprints to image topography
and surface structure.
Operational since 1997: Numerous missions for vegetation, solid earth studies. Flown in Greenland in 2007 in NASA’s P3-B.
LVIS capability for Greenland 2009: 2 km-wide swath. 25 m-wide footprints. 3-4cm range precision 1-2m horizontal geolocation accuracy. Contiguous footprints along and across track. Tx&Return waveforms (10 bit, 1Gsamp/s) for each shot Quicklook data in 1-2 months, final data in <6 months. Plenty of link margin to penetrate through clouds.
2 km
10 km
Nominal operating mode of LVIS
Example LVIS Waveform Collected over Jakobshavn Glacier, 2007
Waveform amplitude (counts)E
leva
tion
abov
e IT
RF0
5 el
lipso
id (
m)
Proposed Greenland Mapping, May 2009Proposed Greenland Mapping, May 2009 Proposed LVIS Mapping in Greenland:
11 flights, 60 ~E-W cross-country flight lines 44 km apart, and 4 ~N-S lines.
3 week mission on DC-8, ~May 2009. Will illuminate and sample ~5% of
Greenland’s surface area.
Each line flown once, cloud issues minimized by flexible planning.
If required, additional flights to cover specifically-targeted areas.
Assumptions: Using NASA’s DC-8 aircraft
40,000’ altitude, 400 knot ground speed 12 hr flights with 10 hrs for science Thule, Sondrestrom, Keflavik base? 300 km
LVIS lines, spaced 44km apart
Coverage ComparisonsCoverage Comparisons
ICESat Repeat 33 day Coverage
LVIS flight track from 9/20/07
300 km
Proposed LVIS ‘09 Coverage (3 weeks)
300 km
Swath CorridorSwath Corridor
Example 2007 LVIS swath (from 25,000’) in vicinity of Jakobshavn with ICESat L3 (cloud free) footprint locations
From 30-40,000’ flying altitude, LVIS achieves a 2 km-wide swath over all of Greenland
Swath is sufficiently wide to capture all ICESat-1 tracks
ICESat L3 Footprint Locations
500m
1km
LVIS Performance in Greenland, 2007LVIS Performance in Greenland, 2007
LVIS data collected on 9/20/07 and 9/21/07 from ~27,000’ in P3-B.
Two ~850km long transects over ice sheet plus ~35 km long transect in the Summit area.
Elevations differences between coincident footprints used to evaluate system performance.
0.00 m 0.00 m 0.01 m
0.08 m 0.11 m 0.06 m
Mean difference
Standard deviation (1)
From: Hofton et al. (2008), Geophysical Research Letters, DOI:10.1029/2008GL035774
Elevation Differences (m)
Per
cent
age
in b
in (%
) With system calibration and multiple GPS base stations, similar performance could be expected in 2009.
Histograms of elevation differences at coincident LVIS footprints:
Along-track Performance of LVIS Data in GreenlandAlong-track Performance of LVIS Data in Greenland
On average, elevation differences between coincident LVIS footprints had means of 0.0m, but along-transect variations of up to 5 cm occurred (likely caused by errors in the atmospheric model applied in the GPS trajectory calculations).
From: Hofton et al. (2008), Geophysical Research Letters, DOI:10.1029/2008GL035774
204419
No obvious degradation in data precision over rough terrain (in this example, the feeder zone of Jakobshavn Glacier)
Comparison of 2007 LVIS Data and ICESat DataComparison of 2007 LVIS Data and ICESat Data
Comparing coincident LVIS (20m footprint) and ICESat (nominal 60m footprint) data in the Summit area.
Although there are offsets between the ICESat L3b-h observations and LVIS, the standard deviations of the differences are <7cm (except L3C).
From: Hofton et al. (2008), Geophysical Research Letters, DOI:10.1029/2008GL035774
