Airborne Surface Profiling of Alaskan Glaciers
Summary
This data set consists of glacier outline, laser altimetry profile, and surface elevation change data for 46 glaciers in Alaska and British Columbia, Canada, measured with an airborne laser altimetry system. Six glaciers in the Alaska Range of central Alaska, two glaciers in the Wrangell Mountains of southcentral Alaska, 11 glaciers in the Chugach Mountains of southcentral Alaska, five glaciers in the Chigmit Mountains of southcentral Alaska, 13 glaciers in the Kenai Mountains of southcentral Alaska (comprising the Harding Icefield), one glacier in the St. Elias Mountains of southeast Alaska, one glacier in the Takhinsha Mountains of southeast Alaska, and seven glaciers in the Coast Mountains of southeast Alaska and British Columbia were profiled between 1994 and 2001. Surface elevation profiles are accurate to about 0.3 m. Long-term elevation changes can be estimated by comparison of these profiles with existing maps.
Citing These Data:
Echelmeyer, K.A., V.B. Valentine, and S.L. Zirnheld. 2002, updated 2004. Airborne surface profiling of Alaskan glaciers. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5RF5RZJ
Overview Table
| Category | Description |
|---|---|
| data format | Fixed width-separated, comma-delimited, or tab-delimited files |
| spatial coverage | Central, southcentral, and southeast Alaska |
| temporal coverage | 1994 - 2001 |
| file size | 1 KB to 5.2 MB |
| Metadata access | View metadata |
| Data access | ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G01378/ |
Table of Contents
1. Contacts
2. Detailed Data Description
3. Data Access
4. References and Related Publications
5. Document Information
1. Contacts
Investigators
Keith A. Echelmeyer
Geophysical Institute
University of Alaska, Fairbanks
Fairbanks, AK 99775
Virginia B. Valentine
Geophysical Institute
University of Alaska, Fairbanks
Fairbanks, AK 99775 USA
Sandra L. Zirnheld
Geophysical Institute
University of Alaska, Fairbanks
Fairbanks, AK 99775 USA
Technical Contact:
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org
2. Detailed Data Description
Data are stored in ASCII text files. See individual data sections below for descriptions of formats.
Glacier Outline Data
Laser Altimetry Profile Data
Glacier Surface Elevation Change Data
Glacier Outline and Profile Trackline Plot
Glacier Outline Data
xxxOUTL.hdr is a Glacier Outline Header file, where "xxx" is the abbreviated name of the glacier. (E.g., BaiOUTL.hdr is the header file for the Baird Glacier outline data.) The glacier outline header files contain the following information:
Glacier Name
World Glacier Inventory (WGI) Glacier Number
Glacier Location
Approximate Center of Glacier
Approximate Length
Glacier Type
Included Tributaries/Regions
Maps used to Generate Outline
Data Fields in File (e.g., easting, northing)
File Name
xxxOUTL.dat is a Glacier Outline Data file, where "xxx" is the abbreviated name of the glacier (e.g., BaiOUTL.dat is the data file for the Baird Glacier outline data). The glacier outline is given in UTM coordinates. The data files contain two fields, either comma-delimited or tab-delimited:
Easting (NAD27, in meters)
Northing (NAD27, in meters)
NAD27 refers to the datum used (the datum is a system of measurement based on earth ellipsoids).
Sample Data Record for BaiOUTL.dat:
BAIRD GLACIER OUTLINE EASTING(NAD27),NORTHING(NAD27) 661274.2091,6338096.646 661323.4619,6338027.883 661371.6796,6337988.571
Laser Altimetry Profile Data
xxxPROF.hdr is a Laser Altimetry Profile Header file, where "xxx" is the abbreviated name of the glacier. For example, BaiPROF.hdr is the header file for the Baird Glacier laser altimetry data. The laser altimetry profile header files contain the following information:
Glacier Name
World Glacier Inventory (WGI) Glacier Number
Glacier Location
Approximate Center of Glacier
Approximate Length
Glacier Type
Geographic Datum
UTM Zone
Profiles
Data Fields in Profile
GPS Processing
Reference
Contact Information
File Names
xxxJDNp.83a is a Laser Altimetry Profile Data file, where "xxx" is the abbreviated name of the glacier, JDN is the Julian day number on which data were collected, and p is the altimetry pass number (e.g., Bai1651.83a is a data file for the Baird Glacier laser altimetry profile data for pass number 1 collected on Julian day number 165). The data files contain four fields, either tab-delimited or fixed-width separated:
Easting (WGS84, in meters)
Northing (WGS84, in meters)
HAE (height above ellipsoid, in meters)
Error (in meters)
WGS84 refers to the datum used (the datum is a system of measurement based on earth ellipsoids).
Sample Data Record for Bai1651.83a:
BAIRD GLACIER LASER ALTIMETRY PROFILE PASS 1 EASTING(m, WGS84) NORTHING(m, WGS84) HAE(m, ht above ellipsoid) ERROR(m) 6.315543600000000e+5 6.330853800000000e+6 4.400000000000000e+0 3.600000000000000e-1 6.315572200000000e+5 6.330860450000000e+6 4.710000000000000e+0 4.300000000000000e-1 6.315578800000000e+5 6.330862100000000e+6 4.500000000000000e+0 1.100000000000000e-1 6.315586800000000e+5 6.330863770000000e+6 4.690000000000000e+0 6.200000000000000e-1
Glacier Surface Elevation Change Data
xxxDZ.hdr is a Glacier Surface Elevation Change Header file, where "xxx" is the abbreviated name of the glacier. For example, BaiDZ.hdr is the header file for the Baird Glacier surface elevation change data.) The glacier surface elevation change header files contain the following information:
Glacier Name
World Glacier Inventory (WGI) Glacier Number
Glacier Location
Approximate Center of Glacier
Approximate Length
Glacier Type
Method For Determining Glacier Elevation Changes
Profiles
Geographic Datum
UTM Zone
Maps Used
Range of Geoid Height
Time Span For Elevation Change
Contact Information
Data Fields
File Name
xxxDZ.dat is a Glacier Surface Elevation Change Data file, where "xxx" is the abbreviated name of the glacier. For example, BaiDZ.dat is the data file for the Baird Glacier surface elevation change data. The data files contain five fields (either tab-delimited or fixed width separated):
Easting (NAD27, in meters)
Northing (NAD27, in meters)
Map Elevation (NGVD29, in meters)
Profile Elevation (NGVD29, in meters)
Elevation Change (in meters)
NAD27 and NGVD29 refer to the datums used (these datums are systems of measurement based on different earth ellipsoids).
Note: The Hubbard glacier surface elevation change data consist of three files:
- HubCanDZ.dat contains elevation change data for areas of Hubbard Glacier that exist in Canada, with the exception of the southeast basin. Profile year is 2000, aerial photograph years are 1976 and 1977.
- HubSEDZ.dat contains elevation change data for the southeast basin, which enters the main basin north of Mount Seattle. Profile year is 2001, aerial photograph years are 1976 and 1979.
- HubUSADZ.dat contains elevation change data for areas of Hubbard Glacier that exist in the United States. Profile year is 2000, aerial photograph year is 1959.
For more information about the Hubbard Glacier DZ files, please refer to the Hubbard Glacier Notes.
Glacier Outline and Profile Trackline Plot
xxxPLOT.jpg is an image file, where "xxx" is the abbreviated name of the glacier. For example, BaiPLOT.jpg is the image file for the Baird Glacier. The image file contains a geographic plot of the glacier outline and the laser altimetry profile tracklines in the NAD27 datum.
Sample Data Record for BaiDZ.dat
BAIRD GLACIER SURFACE ELEVATION CHANGES EASTING(m,NAD27) NORTHING(m,NAD27) MAP ELEVATION(m,NGVD29) PROFILE ELEVATION(m,NGVD29) ELEVATION CHANGE(m) 6.422415500000000e+5 6.337055800000000e+6 6.096000000000000e+2 5.428180300000000e+2 -6.678000000000000e+1 6.417041100000000e+5 6.336794900000000e+6 5.791200000000000e+2 5.170471300000000e+2 -6.207000000000000e+1 6.429674300000000e+5 6.337508700000000e+6 6.400800000000000e+2 5.784238900000000e+2 -6.166000000000000e+1
File Size
File sizes range from 1 KB to 5.2 MB
Spatial Coverage
East Fork Toklat, Gulkana Glacier, MIddle Toklat, Muldrow, Ruth, and Scott Peal Toklat Glaciers are in central Alaska, in the Alaska Range.
Kennicott and Nabesna Glaciers are in southcentral Alaska, in the Wrangell Mountains.
Bear Lake, Bering Glacier-Bagley Icefield, Columbia, Harvard, Knik, Tazlina, Valdez, Wolverine, Worthington, Wortmanns, and Yale Glaciers are in southcentral Alaska, in the Chugach Mountains.
Double, Shamrock, Tanaina, Tuxedni, and Turquoise Glaciers are in southcentral Alaska, in the Chigmit Mountains.
Aialik, Bear, Chernof, Dinglestadt, Exit, Holgate, Kachemak, Little Dinglestadt, McCarty, Northeastern, Northwestern, Skilak, and Tustumena Glaciers are in southcentral Alaska, in the Kenai Mountains, and comprise the Harding Icefield.
Hubbard Glacier is in the St. Elias Mountains, in southeast Alaska.
Muir Glacier is in southeast Alaska, in the Takhinsha Mountains.
Baird, LeConte, Lemon Creek, Llewellyn, Mendenhall, North Dawes, and Triumph Glaciers are in southeast Alaska, in the Coast Mountains.
| GLACIER (Abbrev.) | LATITUDE (N) | LONGITUDE (W) | WGI GLACIER NUMBER* |
| AIALIK (Aia) | 59.96700 | 149.81700 | US2N31850000 |
| BAIRD (Bai) | 57.23330 | 132.37500 | US2P00101800 |
| BEAR (Bea) | 60.05000 | 149.66700 | US2N32050000 |
| BEAR LAKE (Blk) | 60.18000 | 149.25000 | US2P00200402 |
| BERING BAGLEY (BerBag) | 60.50000 | 142.50000 | US2N00700001 |
| CHERNOF (Che) | 59.85800 | 150.41700 | US2N28020000 |
| COLUMBIA (Col) | 61.30000 | 146.88330 | US2T00200627 |
| DINGLESTADT (Din) | 59.75000 | 150.50000 | US2N28080000 |
| DOUBLE (Dou) | 60.66700 | 152.66700 | US2N10499990 |
| EXIT (Exi) | 60.16700 | 149.70000 | US2N32630000 |
| GULKANA (Gul) | 63.27000 | 145.42000 | US2O01200001 |
| HARVARD (Har) | 61.40000 | 147.38000 | US2T00200628 |
| HOLGATE (Hol) | 59.86700 | 149.91700 | US2N31680000 |
| HUBBARD (Hub) | 60.50000 | 139.50000 | US2T00300001 |
| KACHEMAK (Kac) | 59.70000 | 150.55000 | US2N28110000 |
| KENNICOTT (Ken) | 61.60000 | 143.05000 | US2N00400604 |
| KNIK (Kni) | 61.35000 | 148.13000 | US2N00600001 |
| LECONTE (Lec) | 57.00000 | 132.33333 | US2T00101803 |
| LEMON CREEK (Lem) | 58.37000 | 134.35000 | US2P00201804 |
| LITTLE DINGLESTADT (Ldg) | 59.66700 | 150.35800 | US2N30140000 |
| LLEWELLYN (Llew) | 59.00000 | 134.17000 | CD2O010DA001 |
| MCCARTY (Mcc) | 59.21700 | 150.78300 | US2N30350000 |
| MENDENHALL (Men) | 58.50000 | 134.53000 | US2T00101805 |
| MUIR 1948 (Mui) | 59.15000 | 136.40000 | US2N75000010 |
| MUIR 1972 (Mui) | 59.15000 | 136.40000 | US2N75000010 |
| MUIR 2000 (Mui) | 59.15000 | 136.40000 | US2N75000010 |
| MULDROW (Mul) | 63.25000 | 150.50000 | US2O47900010 |
| NABESNA (Nab) | 61.92000 | 143.08000 | US2O01200002 |
| NORTH DAWES (NDw) | 57.63000 | 133.00000 | US2N84200500 |
| NORTHEASTERN (Nea) | 59.80000 | 149.96700 | US2N31350000 |
| NORTHWESTERN (Nwn) | 59.88300 | 150.05000 | US2N31250000 |
| RUTH (Rut) | 62.98000 | 150.73000 | US2N18503000 |
| SHAMROCK (Sha) | 61.05000 | 152.83300 | US2N11800010 |
| SKILAK (Ski) | 60.16700 | 150.01700 | US2N26450000 |
| TANAINA (Tan) | 60.91700 | 152.83300 | US2N10605000 |
| TAZLINA (Taz) | 61.50000 | 146.58330 | US2N00400602 |
| TOKLAT 1-East Fork (TEF) | 63.42000 | 149.67000 | US2O46000100 |
| TOKLAT 2-Middle (TkM) | 63.38000 | 149.91000 | US2O46200100 |
| TOKLAT 3-Scott Peak (TSP) | 63.38000 | 150.12000 | US2O46300100 |
| TRIUMPH (Tri) | 57.44000 | 132.28000 | CD2N001EA555 |
| TURQUOISE (Tur) | 60.78300 | 153.66700 | US2O16100010 |
| TUSTUMENA (Tus) | 59.95000 | 150.25000 | US2N27250000 |
| TUXEDNI (Tux) | 60.12000 | 153.12000 | US2N09100010 |
| VALDEZ (Val) | 61.29000 | 146.20000 | US2N00500501 |
| WOLVERINE (Wol) | 60.41670 | 148.90000 | US2P00200411 |
| WORTHINGTON (Wor) | 61.16667 | 145.79170 | US2N00400603 |
| WORTMANNS (Wrt) | 60.95000 | 145.70000 | US2N00500502 |
| YALE (Yal) | 61.32000 | 147.38000 | US2T00200629 |
*World Glacier Inventory Number
Spatial Coverage Map
Projection
Universal Transverse Mercator (UTM) projection.
Temporal Coverage
Glaciers were profiled in May 1994; May and June 1995; June 1996; May, June, and August, 2000; and May and June, 2001.
Error Sources
Accuracy of the elevation data is typically 0.3 m or better. Error sources include GPS-determined elevation of the aircraft, and pitch and roll of the aircraft. Accuracy of the profile and elevation change data is approximately 5 m, due to map and digitization errors. Please refer to the following for additional quality and accuracy information:
Echelmeyer, K.A., W.D. Harrison, C.F. Larsen, J. Sapiano, J.E. Mitchell, J. DeMallie, B. Rabus, G. Adalgeirsdottir, and L. Sombardier. 1996. Airborne Surface Profiling of Glaciers: a Case-Study in Alaska. J. Glaciol., 42, 142:538-546.
Supporting Online Material for Arendt, A.A., K.A. Echelmeyer, W.D. Harrison, C.S. Lingle, and V.B. Valentine. 2002. Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level. Science, 297:382-386.
3. Data Access
Data are available via ftp.
Data Acquisition Methods
This study used a laser altimeter for measuring the distance from a small aircraft to the glacier surface, a gyro and compass for determining the pointing direction of the laser beam, and continuous kinematic Global Positioning System (GPS) equipment for determining the exact position of the aircraft during the flight over a glacier. Carrier phase measurements were made once per second with two GPS receivers. The laser altimeter (ranger) operated at 905 nm, and sampled at 25 Hz, which corresponds to a measurement interval of about 1.2 m along the surface at a typical aircraft speed of 30m/s. The laser beam footprint diameter was 0.18 m at a distance of 100 m. Reflections were obtained at a maximum distance of 500 m from snow and approximately 200 m from ice, rock, and vegetation. The orientation of the beam was measured by a vertical-axis gyro and a magnetic compass, each sampled at 25 Hz.
The data were stored by an onboard computer and by the GPS receivers, and later processed to give an elevation profile along a specific track on the surface of the glacier. The measured glacier surface elevations were compared to map elevations at the same coordinates to obtain elevation changes over the period of time between the map photo date and the laser profiling date. The glacier profiles were compared to contours on 15-min US Geological Survey (USGS) and Canadian Department of Energy, Mines, and Resources topographic maps made from aerial photographs acquired in the 1950s to early 1970s (depending on location). The investigators digitized contour lines on topographic maps using a Numonics digitizing board and Sigma Scan software. A cubic spline was fit to the contour points to increase the data density. Where a laser altimetry profile crossed a contour line, the nearest profile point to any of the contour points (original or interpolated) was taken as the crossing point (these points were within a few meters horizontally of each other). The measured glacier surface elevation from the profile was compared to the elevation of the contour line from the map. The profile elevation, in height above the ellipsoid, was corrected to the map datum (NGVD29) by subtracting the height of the geoid at the crossing point coordinates (source: NGS Alaska Geoid93 Model or NGS Alaska Geoid99 Model).
4. References and Related Publications
Echelmeyer, K.A., W.D. Harrison, C.F. Larsen, J. Sapiano, J.E. Mitchell, J. DeMallie, B. Rabus, G. Adalgeirsdottir, and L. Sombardier. 1996. Airborne Surface Profiling of Glaciers: a Case-Study in Alaska. J. Glaciol., 42, 142:538-546.
Sapiano, J.J., W.D. Harrison, and K.A. Echelmeyer. 1998. Elevation, Volume and Terminus Changes of Nine Glaciers in North America. J. Glaciol., 44, 146:119-135.
Arendt, A.A., K.A. Echelmeyer, W.D. Harrison, C.S. Lingle, and V.B. Valentine. 2002. Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level. Science, 297:382-386.
5. Document Information
Document Creation Date
September 18, 2002
Document Revision Date
April 21, 2004
Document URL
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