Quantifying the Impact of Adding High-Grade Inertial Measurements to Long-Baseline Aircraft GPS Positioning: Application to Airborne Gravimetry

Theresa M. Damiani and Gerald Mader

Abstract:	The National Geodetic Survey’s (NGS’s) Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program plans to collect airborne gravity data across the entire U.S. and its holdings over the next decade. The goal is to build a geoid accurate to 1-2 cm to use as the next national vertical datum in 2022. An accurate airborne gravity survey of the nation has been proven to be the key to accomplishing that goal. To achieve the best airborne gravity data accuracy possible, the high-precision position solutions for the aircraft must also provide accurate velocities and accelerations to be used in calculating the gravity corrections. From 2008 until 2011, GRAV-D’s missions were flown with a Micro-g LaCoste TAGS gravimeter, NovAtel OEMV-series GPS receiver, and a tactical grade Applanix POS-AV 510 (equipped with “IMU-6” Litton-200 inertial unit) on board the aircraft. In 2011, GRAV-D upgraded from the tactical system to a navigation grade NovAtel SPAN-SE system (equipped with a Honeywell MicroIRS IMU). During the switchover in 2011, GRAV-D flew twenty-seven, 4-hour flights with both IMUs on board the aircraft. This survey was over NY, Lake Ontario, and a small part of Canada, done as part of our Great Lakes focus. This survey offers a unique opportunity to examine the quality of positioning attainable on a series of long baseline (400-500 km) flights. A minimum of four different position products will be compared: Differential GPS-only, PPP GPS-only, Tightly-coupled Tactical IMU plus GPS, and Tightly-coupled Navigation IMU plus GPS. Validation of the results can be done by using each set of position solutions to calculate the gravity over Lake Ontario. The best positioning result will yield a gravity result that more closely resembles the best-available gravity models of the United States. We anticipate that using Differential and PPP GPS-only methods will produce similar gravity results and that the addition of either IMU’s data will improve upon GPS-only trajectories, similar to results from the two 2008 flights used for NGS’ Kinematic GPS Challenge(Damiani, et al. 2013, Proceedings of ION GNSS+). After verifying those previous conclusions, but this time on a much larger scale, we will discuss the impact of using a tactical- vs navigation-grade IMU on the quality of the final trajectories and gravity results. The results of this work will serve as guidance for other remote sensing groups who are using or considering the use of inertial measurements in their aircraft positioning.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	609 - 626
Cite this article:	Damiani, Theresa M., Mader, Gerald, "Quantifying the Impact of Adding High-Grade Inertial Measurements to Long-Baseline Aircraft GPS Positioning: Application to Airborne Gravimetry," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 609-626.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In