Glossary

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A* Path Planning(also: A-star algorithm, A* search)

A classic graph-search algorithm (Hart, Nilsson, and Raphael, 1968) that finds the shortest or lowest-cost path between two points by combining the cost already travelled with a heuristic estimate of the remaining distance. In assistive indoor navigation for blind travellers, A*…

Cascading classifier(also: Staged classifier, Multi-stage classifier)

A machine learning architecture that applies progressively more computationally expensive analysis stages, with each stage filtering out easy-to-classify cases so that only ambiguous instances proceed to deeper analysis. In accessibility applications, cascading classifiers…

Collision Prediction(also: Collision risk prediction, Trajectory prediction)

The task of estimating the future trajectories of surrounding pedestrians and obstacles and determining whether any of them will intersect with a user's own future position within a short prediction horizon (typically 2–4 seconds). In assistive technology for blind travellers,…

Color Histogram(also: Colour histogram, Histogram tracking)

A statistical summary of the distribution of colour values across the pixels of an image or image region, often computed in a perceptual colour space such as Lab. In assistive computer-vision systems for blind users, colour histograms are used to re-identify and track a specific…

Dynamic Time Warping(also: DTW)

An algorithm for measuring similarity between two temporal sequences that may vary in speed or timing. Dynamic time warping aligns sequences by warping the time axis to find the optimal match, making it robust to variations in how quickly gestures are performed. DTW is commonly…

Hybrid automaton(also: Hybrid state machine)

A computational model that combines discrete state transitions with continuous dynamics, used in interactive systems to govern object behaviours based on multiple users's simultaneous inputs. In collaborative virtual environments for autism intervention, hybrid automata control…

Multi-Objective Optimization(also: Many-Objective Optimization, Pareto Optimization)

A computational approach to finding solutions that simultaneously satisfy multiple, potentially conflicting goals. Unlike single-objective optimization which seeks one best answer, multi-objective optimization produces a set of trade-off solutions where improving one objective…

Outlier detection(also: Anomaly detection, Novelty detection)

An algorithmic technique that identifies data points or behaviors that deviate significantly from expected patterns, used in fraud detection, quality assurance, CAPTCHAs, and crowd labor platforms. People with disabilities are disproportionately flagged as outliers because…

Particle filter(also: Sequential Monte Carlo, Monte Carlo localization)

A probabilistic algorithm that estimates a user's position by maintaining a set of weighted hypothetical locations (particles) and updating them based on sensor observations such as Bluetooth beacon signal strengths. In indoor navigation for people with visual impairments,…

Pedestrian dead reckoning(also: PDR, Inertial navigation, Step-and-heading)

A localization technique that estimates a person's position by counting their steps (to determine distance) and detecting turns (to determine heading changes) from a known starting point, using inertial sensors in a smartphone or wearable device. For blind indoor navigation,…

RANSAC(also: Random Sample Consensus)

An iterative algorithm (Fischler and Bolles, 1981) for fitting a mathematical model to data that contains a significant proportion of outliers. In accessibility-focused indoor navigation systems, RANSAC is commonly used to detect the floor plane from a LiDAR point cloud — points…

Random Forest Classifier(also: Random Forest)

A machine learning algorithm that creates multiple decision trees during training and outputs the class that is the mode of the individual trees predictions. Random forests are widely used in gesture recognition, activity recognition, and other classification tasks in assistive…

Singular Value Decomposition(also: SVD)

A mathematical technique that decomposes a matrix into three component matrices, used to reduce high-dimensional data to its most important features while preserving essential relationships. In accessibility research, SVD is a core component of Latent Semantic Analysis and has…

Watershed Algorithm(also: Watershed Segmentation, Watershed Transform)

An image segmentation technique inspired by geographical hydrology, where the gradient magnitude of an image is treated as a topographical surface. The algorithm simulates water flowing downhill from each pixel to local minima, forming catchment basins that define segmented…

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