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. IceBridge LVIS L0 Raw Ranges. Version 1.0. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at NSIDC. Digital media. 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

File and Directory Structure

File Naming Convention

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

Volume

Data volume for the full data set is approximately 5.5 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

Related Data Collections

Related Web Sites

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

Document URL

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