Navigation Facility for High Accuracy Offline Trajectory and Attitude Estimation in Airborne Applications

Abstract

The paper focuses on a navigation facility, relying on commercial-off-the-shelf (COTS) technology, developed to generate high-accuracy attitude and trajectory measurements in postprocessing. Target performance is cm-level positioning with tenth of degree attitude accuracy. The facility is based on the concept of GPS-aided inertial navigation but comprises carrier-phase differential GPS (CDGPS) processing and attitude estimation based on multiantenna GPS configurations. Expected applications of the system include: (a) performance assessment of integrated navigation systems, developed for general aviation aircraft and medium size unmanned aircraft systems (UAS); (b) generation of reference measurements to evaluate the flight performance of airborne sensors (e.g., radar or laser); and (c) generation of reference trajectory and attitude for improving imaging quality of airborne remote sensing data. The paper describes system architecture, selected algorithms for data processing and integration, and theoretical performance evaluation. Experimental results are also presented confirming the effectiveness of the implemented approach.

Differential GNSS and Vision-Based Tracking to Improve Navigation Performance in Cooperative Multi-UAV Systems

“…Instead, both pitch and roll errors are positively impacted by increasing separation, due to the fact that one of the unit vectors tends to be normal to the first or second body axis, as ∆ε approaches 90°. In fact, the latter geometry represents an optimal compromise in terms of accuracy for all the three angles, which represents a well known result exploited in designing single vehicle multi-antenna GPS configurations [29,30,31]. For example, at 100 m baseline we have an error standard deviation of 0.4° for heading, and of 1° for roll and pitch.…”

“…While this uncertainty would correspond to a very rough angular accuracy, in the case of short baselines among rigidly mounted antennas on a single aerial platform [29,30,31], in our case a fine angular accuracy can still be attained by increasing the baselines between the chief and the deputies, thus converting position uncertainties into relatively small angular errors. …”

“…The developed concept is to use the required formation of UAVs to build virtual navigation sensors that provide additional measurements, which are based on DGPS among flying vehicles and visual information and are not affected by magnetic and inertial disturbances. The architecture exploits cooperative GPS, as in multi-antenna attitude estimation architectures [29,30,31]. In particular, while the latter ones exploit carrier phase processing and short baselines (known by calibration) between antennas rigidly mounted on the vehicle, the new approach described in this paper is to exploit differential GPS using antennas embarked on different vehicles, where the exact geometry among them is unknown, but the line of sight between antennas can be estimated by vision sensors.…”

Small Multicopter-UAV-Based Radar Imaging: Performance Assessment for a Single Flight Track

“…Depending on the working environment, platform dynamics and receiver quality, two different types of CDGPS solutions can be obtained, i.e., fixed or float solutions [30]. The former is the most accurate one, being able to guarantee up to sub-cm accuracy in the determination of the relative position between the receivers, exploiting the property of carrier-phase ambiguities to become, under suitable measurement combinations and for properly designed receivers, integer numbers.…”

Small-UAV Radar Imaging System Performance with GPS and CDGPS Based Motion Compensation

“…Relative positioning and ambiguity resolution are herein faced in post processing by means of the open-source software RTKlib [31] Specifically, "Post-Processing Kinematic" (PPK) [27] is implemented by using the RTKPOST [20], which processes single-frequency differential observables. Basic equations for the problem at hand can be found in [20] Note that, depending on the working environment, platform dynamics and receiver quality, two different types of CDGPS solutions can be obtained, i.e., fixed or float solutions [32] In the experiments presented in this paper, the position of the UAV with respect to the reference station is estimated with an accuracy ranging from several cm to less than one cm. The better accuracy is achieved when the fixed solution is available, i.e., integer ambiguities are computed [33].…”