Gravity-lidar study for 2006: Refined gravity field for the North-Central Gulf of Mexico

Abstract

To determine a more accurate geoid model for North America, several refinements must occur in theory and data holdings. This paper focuses on the improvements to the data to provide a consistent, seamless gravity field for such a geoid model, particularly in the poorly covered littoral regions. A LaCoste-Romberg Air-Sea Gravimeter II from the Naval Research Laboratory was loaded onto the NOAA Citation II aircraft to collect data in the northern Gulf of Mexico region in January 2006. An Applanix IMU was mounted onto the gravimeter to provide information about aircraft movement in addition to the dual GPS receivers and antennas. NASA’s Laser Vegetation Imaging Sensor was also mounted to collect lidar profiles nadir to the aircraft flight lines. Data were collected in 41 north-south lines spaced at 10 km and at 10.5 km altitude. Each was 500 km long; hence, the covered region is 400 km by 500 km. Individual flights were processed for all corrections, and a 420 second filter was applied to dampen out most of the noise. The resulting profiles agree at crossovers at about 4 mgal RMS, which indicates 3 mgal accuracy along the profiles. The resulting grid of gravity compares very favorably with upward-continued surface gravity. The differences appear to be related to either geophysical or oceanographic sources and represent a potential improvement in resolving ambiguities between mean sea surface and geoid models. Further refinements will be made when GPS/IMU data are processed and a comparison is made with the LVIS data and an available dynamic topography model.