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Data Set ID:

IceBridge UAF GPS/IMU L1B Corrected Position and Attitude Data, Version 1

This data set contains Global Positioning System (GPS) and Inertial Measurement Unit (IMU) positioning and orientation measurements for the University of Alaska Fairbanks Glacier LIDAR system campaigns. The data were collected as part of Operation IceBridge funded aircraft survey campaigns.

Geographic Coverage

  • Platform Characteristics > Attitude Characteristics
Spatial Coverage:
  • N: 72, S: 55, E: -130, W: -156

Spatial Resolution:
  • Varies x Varies
Temporal Coverage:
  • 19 August 2009 to 12 September 2011
Temporal Resolution: Varies
Data Format(s):
  • ASCII Text
Platform(s) AIRCRAFT, DHC-3
Version: V1
Data Contributor(s): Chris Larsen

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Larsen, C. 2011. IceBridge UAF GPS/IMU L1B Corrected Position and Attitude Data, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].

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Detailed Data Description


The data files are in ASCII format.

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File and Directory Structure

Data files are organized on the HTTPS site,

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File Naming Convention

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




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
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File Size

Data files range from approximately 45 MB to 251 MB.

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The total data set volume is approximately 3.6 GB.

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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

Varies, measured in decimal degrees longitude and latitude, eight decimal places.

Projection and Grid Description

Geographic, WGS-84

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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.

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Parameter or Variable

Parameter Description

Parameters contained in UAF GPS/IMU L1B Corrected Position and Attitude data files are described in Table 2. Columns 1 to 7 in Table 2 represent columns left-to-right in the data. Columns are not numbered in the data files.

Table 2. Parameter Description and Units
Column Description Units
1 Time UTC
2 Latitude Degrees
3 Longitude Degrees
4 Height Meters
5 Roll Degrees
6 Pitch Degrees
7 Heading Degrees

Sample Data Record

Below is an excerpt of the data file IPUAF1B_ascii_DHC-3_20110530_022658_1.pos. The seven fields in each record correspond to the columns described in Table 2.

sample data record

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Software and Tools

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

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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.

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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
  2. GPS base station coordinates are found using Online Positioning User Service (OPUS). For further information on OPUS, see 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.

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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.

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References and Related Publications

Contacts and Acknowledgments

Chris Larsen
Geophysical Institute
University of Alaska Fairbanks
903 Koyukuk Drive
Fairbanks, Alaska 99775 USA


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.

Document Information


08 March 2013

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