National Aeronautics and Space Administration

Wallops Flight Facility

Aircraft Position and Attitude

The ATM group uses a variety of position and orientation systems while on an aircraft.  Our main system for determining aircraft attitude is an Applanix 610 V6 PCS with a type 21 IMU, combined with JAVAD GNSS receivers for aircraft positioning.

The ATM group takes great care in limiting the aircraft attitude and positioning error. This is done by precisely measuring the GPS antenna phase center (i.e. the effective location of the the GPS antenna when taking into consideration the electro-magnetic influence of the aircraft fuselage) and then calculating the offset between the antenna phase center and the Applanix IMU and ATM instrument. These measurements are made using precise surveying equipment and multi-hour GPS occupation time to determine the phase center and instrument offsets to millimeter precision.

Determination of the GPS antenna phase center on the NASA DC-8 aircraft.

briaskThumb_POS_LV_complete

Applanix 610 IMU system

The Applanix POS system is the foremost commercial GNSS-Inertial solution for airborne direct georeferencing. Used with digital cameras, film cameras, LIDAR systems, SAR systems and digital scanners, POS AV precisely measures aerial sensor position and orientation hundreds of times each second, accounting for all motion variables at the exact moment of data capture. In real time or refined in post-processing with the highly productive POSPac Mobile Mapping Suite (MMS) software, data is used to accurately georeference sensor data to the Earth or local mapping frame without ground information, eliminating time-consuming aerotriangulation steps. POS AV is ideally suited to support precision mapping work, especially in inhospitable environments and in rapid response capacities where ground control data may be unavailable or physically impossible to collect.

POS AV with 610 IMU type 21 post processed
Position (m) <0.1 H <0.2 V
Velocity (m/s) 0.0050
Roll & Pitch (deg) 0.00255
True Heading^2 (deg) 0.0050

More information about the Applanix system can be found here: http://www.applanix.com/products/posav.htm

Other attitude systems used by the ATM group include a Novatel span CPT IMU and a Vectornav GPS+IMU.