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.

Larsen, Chris. 2011, updated current year. IceBridge UAF GPS/IMU L1B Corrected Position and Attitude Data, [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://nsidc.org/data/ipuaf1b.html.

Overview

Platform	DeHavilland Otter DHC-3
Sensor	Oxford Technical Solutions Inertial+2 Inertial Measurement Unit Trimble R7 Geodetic GPS Receiver
Spatial Coverage	Alaska
Spatial Resolution	Decimal degrees latitude and longitude
Temporal Coverage	19 August 2009 to present
Temporal Resolution	Annual
Parameters	Time Latitude Longitude Height Roll Pitch Heading
Data Format	ASCII
Metadata Access	View Metadata Record
Data Access	FTP

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Chris Larsen
Geophysical Institute
University of Alaska Fairbanks
903 Koyukuk Drive
Fairbanks, Alaska 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

Acknowledgements

This program has been supported by grants from NASA, NOAA and NSF. Current support comes from NSF Arctic Natural Sciences grant ARC-0612537 and from NASA's Operation Ice Bridge, Earth Science Project Office, Grant NNX09AP54G.

2. Detailed Data Description

Format

The data files are in ASCII format.

File and Directory Structure

Data files are organized on the FTP site, ftp://n4ftl01u.ecs.nasa.gov/SAN2/ICEBRIDGE_FTP/, as described in Figure 1.

File Naming Convention

The data files are named according to the following convention and as described in Table 1:

IPUAF1B_ascii_DHC-3_20110530_022658_1.pos

IPUAF1B_ascii_DHC-3_YYYYMMDD_xxxxxx_x.pos

Where:

Table 1. File Naming Convention

Variable	Description
IPUAF1B	Short name for IceBridge UAF GPS/IMU L1B Corrected Position and Attitude Data
ascii	Indicates ASCII data file
DHC-3	DeHavilland Otter aircraft
YYYY	Four-digit year of data collection
MM	Two-digit month of data collection
DD	Two-digit day of data collection
xxxxxx_x	Hour, minute and second of start time of collection
.pos	Indicates positional data

File Size

Data files range from approximately 45 MB to 251 MB.

Volume

The total data set volume is approximately 3.6 GB.

Spatial Coverage

Spatial coverage for the UAF GPS/IMU L1B Corrected Position and Attitude data:

Southernmost Latitude: 55° N
Northernmost Latitude: 72° N
Westernmost Longitude: 156° W
Easternmost Longitude: 130° W

Spatial Resolution

Decimal degrees longitude and latitude, eight decimal places.

Projection and Grid Description

Geographic, WGS-84

Temporal Coverage

These data were collected as part of NASA Operation IceBridge funded campaigns from 19 August 2009 to the present.

Temporal Resolution

IceBridge campaigns are conducted on an annual repeating basis. Alaska campaigns are conducted during May, June, July, August, and September.

Parameter or Variable

Parameter Description

3. Data Access and Tools

Data Access

Data are available via FTP.

Software and Tools

The data files may be opened by any ASCII text reader.

4. Data Acquisition and Processing

These data are position and attitude of the inertial platform. They are recorded at 100 Hz by an Oxford Technical Solutions (OxTS) Inertial+2 IMU coupled with a Trimble R7 GPS.

Data Acquisition Methods

The IMU data are recorded on the IMU at 100 Hz. The GPS data are recorded on the GPS at 5 Hz. The two datasets are merged in post processing to provide the .pos files with 100 Hz resolution.

Derivation Techniques and Algorithms

Processing Steps

The following processing steps are performed by the data provider.

1. All GPS processing of the aircraft position uses L1 frequency 1575.42 MHz and L2 frequency 1227.6 MHz data recorded at 5 Hz, processed with the TRACK GPS differential phase kinematic positioning program, a module of the GAMIT/GLOBK software programs from the Department of Earth Atmospheric and Planetary Sciences, MIT. For further information on TRACK, see http://geoweb.mit.edu/~tah/track_example.
2. GPS base station coordinates are found using Online Positioning User Service (OPUS). For further information on OPUS, see http://www.ngs.noaa.gov/OPUS/. The kinematic processing and the laser shot point coordinates are referenced to these base station coordinates.
3. The IMU raw data are post processed and blended with the GPS post processed solution using OxTS program "RTpostprocess". The results are output from this program in the .pos format provided.

Error Sources

Typical errors sources include the normal GPS post processing kinematic solution concerns, including loss of lock from aircraft maneuvers, and ionosphere noise.

Sensor or Instrument Description

The main components of the GPS/IMU are an Oxford Technical Solutions Inertial+2 inertial measurement unit, and a Trimble R7 geodetic GPS receiver.

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 3.

Table 3. Acronyms and Abbreviations

Acronym	Description
ASCII	American Standard Code for Information Interchange
ASPRS	American Society for Photogrammetry and Remote Sensing
CIRES	Cooperative Institute for Research in Environmental Science
FTP	File Transfer Protocol
GPS	Global Positioning System
IMU	Inertial Measurement Unit
ITRF	International Terrestrial Reference Frame
L1B	Processing Level-1B
L1	L1 is a civilian-use GPS signal broadcast on the 1575.42 MHz frequency, that currently contains the course acquisition signal used by all current GPS users. Also known as L1C.
L2	L2 is a civilian-use GPS signal broadcast on the 1227.6 MHz frequency. Also known as L2C.
NASA	National Aeronautics and Space Administration
NOAA	National Oceanic and Atmospheric Administration
NSF	National Science Foundation
NSIDC	National Snow and Ice Data Center
OPUS	Online Positioning User Service
OxTS	Oxford Technical Solutions
UAF	University of Alaska Fairbanks
URL	Uniform Resource Locator
UTM	Universal Transverse Mercator
WGS-84	World Geodetic System 1984

Document Creation Date

08 March 2013

Document Revision Date

Document URL

http://nsidc.org/data/docs/daac/icebridge/ipuaf1b/index.html