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IceBridge LVIS L0 Raw Ranges

This data set contains raw laser altimeter, Inertial Measurement Unit (IMU), Global Positioning System (GPS), and camera data over Greenland and Antarctica taken from the NASA Land, Vegetation, and Ice Sensor (LVIS). The data were collected as part of Operation IceBridge funded campaigns.

Operation IceBridge products may include test flight data that are not useful for research and scientific analysis. Test flights usually occur at the beginning of campaigns. Users should read flight reports for the flights that collected any of the data they intend to use. Check IceBridge campaign Flight Reports for dates and information about test flights.

Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

Citing These Data

The following example shows how to cite the use of this data set in a publication.

Blair, Bryan, and Michelle Hofton. 2011, updated 2014. IceBridge LVIS L0 Raw Ranges. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://nsidc.org/data/ilvis0.html.

Overview

Platform

NASA DC-8
NASA P-3B
NASA HU-25C Falcon Jet
NSF/NCAR G-V
NASA LARC King Air B-200

Sensor

Land, Vegetation, and Ice Sensor (LVIS)

Spatial Coverage

Greenland, Antarctica

Spatial Resolution

Nominally 20 meters

Temporal Coverage

14 April 2009 to the present.

Temporal Resolution

Seasonal

Parameters

Altimeter measurements of terrain elevation

Data Format

Binary IMU files
JPEG images
Binary GPS files
Binary altimeter files
ASCII aircraft attitude data

Metadata Access

View Metadata Record

Data Access

FTP

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Bryan Blair
Laser Remote Sensing Laboratory, Code 694
NASA Goddard Space Flight Center
Greenbelt, MD 20771

Michelle Hofton
Department of Geography
2181 LeFrak Hall
University of Maryland
College Park, MD 20742

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

Acknowledgements

This work was supported by NASA Grant Number NNX11AH69G, LVIS: A Topographic Mapping Capability for IceBridge.

2. Detailed Data Description

Format

Files in the LVIS Level-0 data set include binary laser altimeter, Inertial Measurement Unit and Global Positioning System data, binary JPEG images, and ASCII text files. All contain raw, unprocessed data.

File and Directory Structure

Data are available on the FTP site in the following directory: ftp://n4ftl01u.ecs.nasa.gov/SAN2/ICEBRIDGE_FTP/ILVIS0_LVISraw_v01/.

Each directory contains data for one IceBridge campaign and is named with its year, location (AN = Antarctica, GR = Greenland), and NASA, for example: /2009_AN_NASA/.

Within each campaign, a directory is named for each Modified Julian Day (MJD) and contains the instrument data collected on that day, for example: /55117/. A tool for conversion between date and MJD is available at http://www.csgnetwork.com/julianmodifdateconv.html.

Within each MJD directory are sub-directories for instruments. These may include some or all of:

  • /rtlvis/ for the LVIS laser altimeter data
  • /applanix/ or /gyro/ for the Inertial Measurement Unit data
  • /camera/ for the high resolution camera images
  • /gps/ for the Global Positioning System data
  • /planedata/ for aircraft position, attitude, and motion data

These directories may have subdirectories corresponding to separate individual instruments. Examples are:

  • /camera/camera1/ and /camera/camera2/
  • /gyro/atm_applanix/ and /gyro/lvis_applanix/
  • /applanix/510/ and /applanix/610/
  • /applanix/LVIS/ and /applanix/AMES/
  • /gps/base/ and /gps/remote/ and /gps/plane/

File Naming Convention

LVIS L0 Raw Ranges data file names for each instrument follow different conventions as described below and in the following tables.

LVIS Altimeter Files

LVIS altimeter files found in /rtlvis/ are binary or ASCII text files with naming conventions as described in Table 1.

Examples:

fpga_20091013_15.47.48_00001.bin
galv_20091013_15.47.48.00001.bin
rtlvis_20091013_15.47.48_00001.bin
status_20091013_15.47.48_00001.bin
telem_20091013_15.47.48_00001.bin
applanix_raw_20091013.bin
log_rtlvis_20091013.txt

aaaaaa_YYYYMMDD_hh.mm.ss_NNNNN.bin
aaaaaa_YYYYMMDD.bin
aaaaaa_YYYYMMDD.txt

Where:

Table 1. LVIS Altimeter File Naming Convention
Variable Description
aaaaaa fpga = Delphi digitizer / scanner code
galv = time and galvanometer position
rtlvis = LVIS digitizer / scanner data
status = binary system status information
telem = binary system status information
applanix_raw = binary status packets from the Applanix IMU/GPS system
log_rtlvis = records all user and real time ground tracking commands
YYYY Four-digit year (GMT) at beginning of data collection
MM Two-digit month (GMT) at beginning of data collection
DD Two-digit day (GMT) at beginning of data collection
hh.mm.ss hh = hour (GMT) at beginning of data collection
mm = minute (GMT) at beginning of data collection
ss = second (GMT) at beginning of data collection
NNNNN sequential number, increments through the data collection period
.bin or .txt indicates binary or ASCII text file

Inertial Measurement Unit Files

Inertial Measurement Unit raw data files in /applanix/ or /gyro/ are binary or ASCII text files with naming conventions as described in Table 2. Note that normal LVIS operating conditions include two IMUs operating concurrently. Thus, two subdirectories are typically present.

Examples:

13Oct09.091
POSAV.001
AMES.015
LVIS.086

AAAAAA.NNN

Where:

Table 2. IMU File Naming Convention
Variable Description
AAAAAA Combined with directory and subdirectory name, identifies the individual instrument.
.NNN NNN = Sequential number. Data collected throughout the flight are separated into a sequence of smaller files according to instrument configuration or in order to limit file size.

Some subdirectories contain the file md5deep.txt. This is an ASCII text file containing the MD5 hash numbers for each file in the subdirectory. It is provided for the user to check the integrity of a binary data file following download.

Image Files

Unprocessed image files found in /camera/ are in standard binary JPEG format, and are named according to the following conventions and as described in Table 3. Note that these raw images are not georeferenced.

Examples:

IMG_5041.JPG
2009_10_16_0001.JPG
LVISCAM_2011_05_11_0001.JPG

Where:

Table 3. Camera Image File Naming Conventions
Variable Description
IMG_XXXX.JPG IMG = image
XXXX = sequential number
JPG = JPEG format
YYYY_MM_DD_XXXX.JPG YYYY = four-digit year
MM = two-digit month
DD = two-digit day
XXXX = sequential number
JPG = JPEG format
LVISCAM_YYYY_MM_DD_XXXX.JPG LVISCAM = LVIS camera
YYYY = four-digit year
MM = two-digit month
DD = two-digit day
XXXX = sequential number
JPG = JPEG format

GPS Files

Raw GPS files under directory /gps/ are named according to the following numerous conventions used by different receiver manufacturers. Files may be binary or ASCII. Multiple and various makes and models of ground based and airborne GPS receivers were in operation during the different LVIS IceBridge campaigns and may be identified by their name included in subdirectory and/or file names. Interested users are referred to those manufacturers for their proprietary file formats. Some file naming conventions are generally described in Table 4 below. The LVIS instrument team converted these proprietary formatted raw data into the standard RINEX format prior to processing with commercially available software. Please contact the LVIS data providers if more information is required.

Where:

Table 4. GPS File Naming Convention
Examples Description
J0080_101309.jps
J078042a.jps
00790329a.jps
20101019_1.jps
J0790508a
.jps = proprietary binary format from Javad receivers, see www.javad.com
(ASCII text file if '.jps' is absent)

JXXX_YYYYYYZ:
optional J = Javad
XXX = receiver identification number
YYYYYY = date as MMDD, MMDDYY, or YYYYMMDD
Z = lower case a-z, or _N, indicating position in a sequence
00443090.PDC .PDC = proprietary binary format from NovAtel receivers (see www.novatel.com)
mgps_01_20091013a.gps mgps*.gps = binary data from the IMU's internal GPS receiver
B1585A09.286
E1585A09.286
S1585A09.286
alm09.286
binary and ASCII files from Ashtec receivers (see www.ashtec.com)

LMMMMNPP.XXX or almPP.XXX:
L = B, E, or S, proprietary Ashtec binary format files
alm = ASCII format almanac file
MMMM = receiver identification number
N = sequential letter
PP = two-digit year
.XXX = day of year

Some subdirectories under /gps/ contain a file or files named similarly to md5deep.txt. These are ASCII text files containing the MD5 hash numbers for each file in the subdirectory. They are provided for the user to check the integrity of their downloaded binary data file(s).

Aircraft Position Files

Aircraft data files under /planedata/ contain aircraft position, attitude, and motion data and are in ASCII format. These are present for Operation IceBridge 2011 Antarctica data only, as they pertain to operations in the Gulfstream-V aircraft. The file naming convention is described in Table 5. No additional documentation is available to accompany these files.

Example:

OIBGVrf01.asc

Where:
Table 5. Aircraft Data File Naming Convention
Variable Description
OIB Operation IceBridge
GV Gulfstream-V aircraft
rfxx xx = sequential operational day number
.asc Indicates ASCII text file

Volume

Data volume for the full data set is approximately 6.5 TB.

Spatial Coverage

Spatial coverage for the IceBridge LVIS campaigns includes the Arctic, Greenland, Antarctica, and surrounding ocean areas. In effect, this represents the coverage noted below.

Arctic / Greenland:
Southernmost Latitude: 60° N
Northernmost Latitude: 90° N
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E

Antarctic:
Southernmost Latitude: 90° S
Northernmost Latitude: 53° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E

Spatial Resolution

Spatial resolution is nominally 20 meters, but varies with aircraft altitude. Laser spot size is a function of beam divergence and altitude. Nominal spot spacing is a function of scan rate and pulse repetition rate.

Projection and Grid Description

International Terrestrial Reference Frame (ITRF 2000), WGS-84 Ellipsoid.

Temporal Coverage

These data were collected as part of Operation IceBridge funded campaigns from 14 April 2009 to the present.

Temporal Resolution

IceBridge campaigns are conducted on an annual repeating basis. Arctic and Greenland campaigns are conducted during March, April, and May, and Antarctic campaigns are conducted during October and November.

Parameter or Variable

The primary data parameter in this data set is raw laser altimeter measurement from the LVIS instrument. Additional supporting parameters include raw GPS and aircraft position, attitude, and motion readings. These files, provided for archival purposes, contain the raw data processed by the LVIS instrument team using proprietary software to create the data sets: IceBridge LVIS Level-1B Geolocated Return Energy Waveforms and IceBridge LVIS Level-2 Geolocated Surface Elevation Product.

3. Data Access and Tools

Data Access

Data are available via FTP.

Software and Tools

No software or tools are provided for the L0 files.

4. Data Acquisition and Processing

As described on the NASA LVIS Web site, a laser altimeter is an instrument that measures range from the instrument to a target object or surface. The device sends a laser beam toward the target, and measures the time it takes for the signal to reflect back from the surface. Knowing the precise round-trip time it takes for the reflection to return yields the range to the target.

Figure 1 shows two examples of return energy waveforms. A simple waveform occurs where the ice surface is relatively smooth within the footprint of the laser pulse (approximately 20 meters in diameter). Mean noise level, provided with the Level-1B data product, provides the threshold relative to which the centroid and all modes are later computed for the Level-2 data product. A complex waveform might be returned from a rougher ice surface and could contain more than one mode, originating from different reflecting surfaces within the laser footprint such as crevasse sides and bottom, open water, large snowdrifts, and other steep or multiple slopes. A complex waveform would be more typically returned from multilevel vegetation landcover such as a forest.

Figure 1. Sample Level-1B Product Waveforms Illustrating Some Possible Distributions of Reflected Light

Data Acquisition Methods

LVIS employs a signal digitizer, disciplined with a very precise oscillator, to measure both the transmitted and reflected laser pulse energies versus time. These digitized and captured photon histories are known as waveforms. For the outgoing pulse, it represents the profile of the individual laser shot, and for the return pulse it records the interaction of that transmitted pulse with the target surface.

Processing of these waveforms yields many products, but the primary is range from the instrument to the Earth's surface and the distribution of reflecting surfaces within the area of the laser footprint. For vegetated terrain these surfaces are tree canopies, branches, other forms of vegetation, and open ground. For cryospheric data these surfaces are snow, ice, crevasses, snowdrifts, sea ice possibly interspersed with open ocean, exposed rock, and water.

LVIS uses a waveform-based measurement technique to collect data instead of just timing detected returns of the laser pulse. The return signal is sampled rapidly, and stored completely for each laser shot. Retaining all waveform information allows post processing of the data to extract many different products. With the entire vertical extent of surface features recorded, metrics can be extracted about the sampled area. An advantage of saving all of the waveform data is that new techniques can be applied to these data long after collection to extract even more information. See the NASA LVIS Web site.

Derivation Techniques and Algorithms

The LVIS L0 data are raw unprocessed data. No derivation techniques, algorithms, or processing steps are used.

Sensor or Instrument Description

As described on the NASA LVIS Web site the Land, Vegetation, and Ice Sensor is an airborne LIDAR scanning laser altimeter used by NASA for collecting surface topography and vegetation coverage data. LVIS uses a signal digitizer with oscillator to measure transmitted and reflected laser pulse energies versus time capturing photon histories as waveforms. The laser beam and telescope field of view scan a raster pattern along the surface perpendicular to aircraft heading as the aircraft travels over a target area. LVIS has a scan angle of approximately 12 degrees, and can cover 2 km swaths from an altitude of 10 km. Typical collection size is 10 to 25 meter spots. In addition to waveform data, GPS satellite data is recorded at ground tie locations and on the airborne platform to precisely reference aircraft position. An IMU is attached directly to the LVIS instrument and provides information required for coordinate determination.

5. References and Related Publications

Blair, J. B., D. L. Rabine., and M. A. Hofton. 1999. The Laser Vegetation Imaging Sensor: A Medium-Altitude, Digitisation-Only, Airborne Laser Altimeter for Mapping Vegetation and Topography, ISPRS Journal of Photogrammetry and Remote Sensing, 54: 115-122.

Hofton, M. A., J. B. Blair, J. B. Minster., J. R. Ridgway, N. P. Williams, J. L Bufton, and D. L. Rabine. 2000. An Airborne Scanning Laser Altimetry Survey of Long Valley, California, International Journal of Remote Sensing, 21(12): 2413-2437.

Hofton, M. A., J. B. Blair, S. B. Luthcke, and D. L. Rabine. 2008. Assessing the Performance of 20-25 m Footprint Waveform Lidar Data Collected in ICESat Data Corridors in Greenland, Geophysical Research Letters, 35: L24501, doi:10.1029/2008GL035774.

Related Data Collections

Related Web Sites

  • LVIS Web site at NASA Goddard Space Flight Center (http://lvis.gsfc.nasa.gov).
  • IceBridge Data Web site at NSIDC (http://nsidc.org/data/icebridge/index.html).
  • IceBridge Web site at NASA (http://www.nasa.gov/mission_pages/icebridge/index.html).
  • ICESat/GLAS Web site at NASA Wallops Flight Facility (http://glas.wff.nasa.gov/).
  • ICESat/GLAS Web site at NSIDC (http://nsidc.org/daac/projects/lidar/glas.html).

6. Document Information

Acronyms and Abbreviations

The acronyms used in this document are listed in Table 6.

Table 6. Acronyms and Abbreviations
Acronym Description
ASCII American Standard Code for Information Interchange
CIRES Cooperative Institute for Research in Environmental Science
ECS NASA Earth Observing System Data and Information System (EOSDIS) Core System
FTP File Transfer Protocol
GPS Global Positioning System
IMU Inertial Measurement Unit
INS Inertial Navigation System
ITRF International Terrestrial Reference Frame
JPEG Joint Photographic Experts Group
L0 Level-0 processing
LIDAR LIght Detection And Ranging
LVIS Land, Vegetation, and Ice Sensor
MD5 Message-Digest Algorithm
MJD Modified Julian Day
NASA National Aeronautics and Space Administration
NSIDC National Snow and Ice Data Center
URL Uniform Resource Locator
WGS 84 World Geodetic System 1984

Document Creation Date

02 October 2012

Document Revision Date

11 February 2014

Document URL

http://nsidc.org/data/docs/daac/icebridge/ilvis0/index.html