scholarly journals WHY THE HORIZON IS IMPORTANT FOR AIRBORNE SENSE AND AVOID APPLICATIONS

2015 ◽  
Vol XL-1/W4 ◽  
pp. 123-130
Author(s):  
C. Minwalla ◽  
K. Ellis
Keyword(s):  
Apparent Horizon ◽  
National Research Council ◽  
Ground Truth ◽  
Flight Test ◽  
Near Miss ◽  
Reference Plane ◽  
Earth Model ◽  
Navigation Systems ◽  
Sensing Element ◽  
Sense And Avoid

The utility of the horizon for airborne sense-and-avoid (ABSAA) applications is explored in this work. The horizon is a feature boundary across which an airborne scene can be separated into surface and sky and serves as a salient, heading-independent feature that may be mapped into an electro-optical sensor. The virtual horizon as established in this paper represents the horizon that would be seen assuming a featureless earth model and infinite visibility and is distinct from the apparent horizon in an imaging sensor or the pilot’s eye. For level flight, non-maneuvering collision course trajectories, it is expected that targets of interest will appear in close proximity to this virtual horizon. This paper presents a model for establishing the virtual horizon and its projection into a camera reference plane as part of the sensing element in an ABSAA system. Evaluation of the model was performed on a benchmark dataset of airborne collision geometries flown at the National Research Council (NRC) using the Cerberus camera array. The model was compared against ground truth flight test data collected using high accuracy inertial navigation systems aboard aircraft on several ’near-miss’ intercepts. The paper establishes the concept of ’virtual horizon proximity’ (VHP), the minimum distance from a detected target and the virtual horizon, and investigates the utility of using this metric as a means of rejecting false positive detections, and increasing range at first detection through the use of a region of interest (ROI) mask centred on the virtual horizon. The use of this horizon-centred ROI was shown to increase the range at first detection by an average factor of two, and was shown to reduce false positives for six popular feature detector algorithms applied across the suite of flight test imagery.

A comparison of two novel approaches for conducting detect and avoid flight test

2021 ◽  
Author(s):  
Kris Ellis ◽  
Iryna Borshchova ◽  
Sion Jennings ◽  
Caidence Paleske
Keyword(s):  
Arrival Time ◽  
Initial Conditions ◽  
National Research Council ◽  
Flight Test ◽  
Threshold Value ◽  
Near Miss ◽  
Approach Distance ◽  
Set Up ◽  
Cross Track ◽  
Collision Trajectory

This paper compares two approaches developed by the National Research Council of Canada to conduct ‘near-miss’ intercepts in flight test, and describes a new method for assessing the efficacy of these trajectories. Each approach used a different combination of flight test techniques and displays to provide guidance to the pilots to set-up the aircraft on a collision trajectory and to maintain the desired path. Approach 1 only provided visual guidance of the relative azimuth and position of the aircraft, whereas Approach 2 established the conflict point (latitude/longitude) from the desired geometry, and provided cross track error from the desired intercept as well as speed cueing for the arrival time. The performance of the approaches was analyzed by comparing the proportion of time where the predicted closest approach distance was below a desired threshold value. The analysis showed that Approach 2 resulted in more than double the amount of time spent at or below desired closest approach distance across all azimuths flown. Moreover, since less time was required to establish the required initial conditions, and to stabilize the flight paths, the authors were able to conduct 50% more intercepts.

scholarly journals IMG-22. A DEEP LEARNING MODEL FOR AUTOMATIC POSTERIOR FOSSA PEDIATRIC BRAIN TUMOR SEGMENTATION: A MULTI-INSTITUTIONAL STUDY

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii359-iii359
Author(s):  
Lydia Tam ◽  
Edward Lee ◽  
Michelle Han ◽  
Jason Wright ◽  
Leo Chen ◽  
...  
Keyword(s):  
Deep Learning ◽  
Posterior Fossa ◽  
Ground Truth ◽  
Learning Model ◽  
Tumor Segmentation ◽  
Dice Similarity Coefficient ◽  
Study Cohort ◽  
Navigation Systems ◽  
Tumor Types ◽  
Deep Learning Model

Abstract BACKGROUND Brain tumors are the most common solid malignancies in childhood, many of which develop in the posterior fossa (PF). Manual tumor measurements are frequently required to optimize registration into surgical navigation systems or for surveillance of nonresectable tumors after therapy. With recent advances in artificial intelligence (AI), automated MRI-based tumor segmentation is now feasible without requiring manual measurements. Our goal was to create a deep learning model for automated PF tumor segmentation that can register into navigation systems and provide volume output. METHODS 720 pre-surgical MRI scans from five pediatric centers were divided into training, validation, and testing datasets. The study cohort comprised of four PF tumor types: medulloblastoma, diffuse midline glioma, ependymoma, and brainstem or cerebellar pilocytic astrocytoma. Manual segmentation of the tumors by an attending neuroradiologist served as “ground truth” labels for model training and evaluation. We used 2D Unet, an encoder-decoder convolutional neural network architecture, with a pre-trained ResNet50 encoder. We assessed ventricle segmentation accuracy on a held-out test set using Dice similarity coefficient (0–1) and compared ventricular volume calculation between manual and model-derived segmentations using linear regression. RESULTS Compared to the ground truth expert human segmentation, overall Dice score for model performance accuracy was 0.83 for automatic delineation of the 4 tumor types. CONCLUSIONS In this multi-institutional study, we present a deep learning algorithm that automatically delineates PF tumors and outputs volumetric information. Our results demonstrate applied AI that is clinically applicable, potentially augmenting radiologists, neuro-oncologists, and neurosurgeons for tumor evaluation, surveillance, and surgical planning.

Flight Test of a Radar-Based Tracking System for UAS Sense and Avoid

2013 ◽  
Vol 49 (2) ◽  
pp. 1139-1160 ◽  
Author(s):  
Domenico Accardo ◽  
Giancarmine Fasano ◽  
Lidia Forlenza ◽  
Antonio Moccia ◽  
Attilio Rispoli
Keyword(s):  
Tracking System ◽  
Flight Test ◽  
Sense And Avoid

The aeromagnetic survey program of the Geological Survey of Canada: contribution to regional geological mapping and mineral exploration

1993 ◽  
Vol 30 (2) ◽  
pp. 243-260 ◽  
Author(s):  
D. J. Teskey ◽  
P. J. Hood ◽  
L. W. Morley ◽  
R. A. Gibb ◽  
P. Sawatzky ◽  
...  
Keyword(s):  
Mineral Exploration ◽  
National Research Council ◽  
High Sensitivity ◽  
Geological Mapping ◽  
Geological Survey ◽  
The Arctic ◽  
Navigation Systems ◽  
Current Standard ◽  
Private Industry ◽  
Aeromagnetic Survey

The aeromagnetic survey operations of the Geological Survey of Canada (GSC) began in 1946, utilizing a magnetometer in a bird system towed by a Royal Canadian Air Force Anson. Subsequent early operations were carried out by the GSC-operated Canso and Aero Commander aircraft. In 1961, the GSC in-house survey team formed the nucleus of a contract surveys group set up to monitor a new program established to complete the aeromagnetic mapping of the Canadian Shield in 12 years on a cost-sharing basis with the provinces. Today, surveys are carried out under contract by light twin-engine aircraft such as the Cessna 404 and even, in some cases, single-engine aircraft that utilize compact computer-controlled data acquisition and navigation systems and inboard magnetometer installations. Early systems were capable of resolution of only a few nanoteslas (nT) compared to the current standard of 0.1 nT or less, and flight path positioning with 35 mm film and photomosaics or topographical maps was extremely challenging. Despite these limitations, the careful selection of survey parameters and attention given to quality control have resulted in a world-class aeromagnetic data base that has contributed significantly to regional geological mapping and to mineral and oil exploration in Canada. Concurrently, the GSC carried out research programs into the development of instrumentation and into processing, interpretation, and enhancement techniques. In 1968, the GSC acquired its own platform, a Beechcraft B80 Queenair, which was used to develop high-sensitivity techniques, and an inboard gradiometer system, which was transferred to private industry in 1983. The GSC, in cooperation with the Flight Research Laboratory of the National Research Council of Canada, has also conducted a program of research into magnetometry and navigation combined with aeromagnetic studies of the Arctic since 1962.

scholarly journals Augmented Marker Tracking for Peri-acetabular Osteotomy Surgery: A Cadaver Study

10.29007/9mbb ◽  
2018 ◽  
Author(s):  
Silvio Pflugi ◽  
Till Lerch ◽  
Rakesh Vasireddy ◽  
Nane Boemke ◽  
Moritz Tannast ◽  
...  
Keyword(s):  
Navigation System ◽  
Ground Truth ◽  
Video Stream ◽  
Cadaver Study ◽  
Optical Tracking ◽  
Host Computer ◽  
Absolute Difference ◽  
Measurement Unit ◽  
Navigation Systems ◽  
Acetabular Fragment

Purpose. To validate a small, easy to use and cost-effective augmented marker-based hybrid navigation system for peri-acetabular osteotomy surgery.Methods. A cadaver study including 3 pelvises (6 hip joints) undergoing navigated PAO was performed. Inclination and anteversion of two navigation systems for PAO were compared during acetabular reorientation. The hybrid system consists of a tracking unit which is placed on the patient’s pelvis and an augmented marker which is attached to the patient’s acetabular fragment. The tracking unit sends a video stream of the augmented marker to the host computer. Simultaneously, the augmented marker sends orientation output from an integrated inertial measurement unit (IMU) to the host computer. The host computer then computes the pose of the augmented marker and uses it (if visible) to compute acetabular orientation. If the marker is not visible, the output from the IMU is used to update the orientation. The second system served as ground truth and is a previously developed and validated optical tracking-based navigation system.Results. Mean absolute difference for inclination and anteversion (N = 360) was 1.34 degrees and 1.21 degrees, respectively. The measurements from our system show a very strong correlation to the ground-truth optical tracking-based navigation system for both inclination and anteversion (0.9809 / 0.9711).Conclusion. In this work we successfully demonstrated the feasibility of our system to measure inclination and anteversion during acetabular reorientation.

scholarly journals A novel method for 3D face symmetry reference plane based on weighted Procrustes analysis algorithm

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Yujia Zhu ◽  
Shengwen Zheng ◽  
Guosheng Yang ◽  
Xiangling Fu ◽  
Ning Xiao ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Facial Asymmetry ◽  
Ground Truth ◽  
Asymmetry Index ◽  
Position Error ◽  
Procrustes Analysis ◽  
Reference Plane ◽  
Anatomical Landmarks ◽  
Angle Error ◽  
Novel Method

Abstract Background We aimed to establish a novel method, using the weighted Procrustes analysis (WPA) algorithm, which assigns weight to facial anatomical landmarks, to construct a three-dimensional facial symmetry reference plane (SRP) for mandibular deviation patients. Methods Three-dimensional facial SRPs were independently extracted from 15 mandibular deviation patients using both our WPA algorithm and the standard PA algorithm. A reference plane was defined to serve as the ground truth. To determine whether the WPA SRP or the PA SRP was closer to the ground truth, we measured the position error of mirrored landmarks, the facial asymmetry index (FAI) error, and the angle error for the global face and each facial third partition. Results The average angle error between the WPA SRP and the ground truth was 1.66 ± 0.81°, which was smaller than that between the PA SRP and the ground truth. The position error of the mirrored landmarks constructed using the WPA algorithm in the global face (3.64 ± 1.53 mm) and each facial partition was lower than that constructed using the PA algorithm. The average FAI error of the WPA SRP was − 7.77 ± 17.02 mm, which was smaller than that of the PA SRP. Conclusions This novel automatic algorithm, based on weighted anatomic landmarks, can provide a more adaptable SRP than the standard PA algorithm when applied to severe mandibular deviation patients and can better simulate the diagnosis strategies of clinical experts.

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