Rotation modulation can significantly improve the navigation accuracies of an inertial navigation system (INS) and a strap-down configuration dominating in this type of INS. However, this style of construction is not a good scheme since it has no servo loop to counteract a vehicle manoeuvre. This paper proposes a rotary upgrading method for a rotational INS based on an inertially stabilized platform. The servo control loop is reconstructed on a four-gimbal platform, and it has the functions of providing both a level stability relative to the navigation frame and an azimuth rotation at a speed of 1:2◦/s. With the platform’s rotation, the observability and the convergence speed of the estimation for the initial alignment can be improved, as well as the biases of the gyroscopes and accelerometers be modulated into zero-mean periodic values. An open-loop initial alignment method is designed, and its detailed algorithms are delivered. The experiment result shows that the newly designed rotational INS has reached an accuracy of 0.38 n mile/h (CEP, circular error probable). The feasibility and engineering applicability of the designed scheme have been validated.

Understanding the factors that influence the quality of unmanned aerial vehicle (UAV)-based products is

a scientifically ongoing and relevant topic. Our research focused on the impact of the interior orientation

parameters (IOPs) on the positional accuracy of points in a calibration field, identified and measured in an

orthophoto and a point cloud. We established a calibration field consisting of 20 materialized points and

10 detailed points measured with high accuracy. Surveying missions with a fixed-wing UAV were carried

out in three series. Several image blocks that differed in flight direction (along, across), flight altitude

(70 m, 120 m), and IOPs (known or unknown values in the image-block adjustment) were composed. The

analysis of the various scenarios indicated that fixed IOPs, computed from a good geometric composition,

can especially improve vertical accuracy in comparison with self-calibration; an image block composed

from two perpendicular flight directions can yield better results than an image block composed from a single

flight direction.