title: GReTA-A Novel Global and Recursive Tracking Algorithm in Three Dimensions.
abstract: Tracking multiple moving targets allows quantitative measure of the dynamic behavior in systems as diverse as animal groups in biology, turbulence in fluid dynamics and crowd and traffic control. In three dimensions, tracking several targets becomes increasingly hard since optical occlusions are very likely, i.e., two featureless targets frequently overlap for several frames. Occlusions are particularly frequent in biological groups such as bird flocks, fish schools, and insect swarms, a fact that has severely limited collective animal behavior field studies in the past. This paper presents a 3D tracking method that is robust in the case of severe occlusions. To ensure robustness, we adopt a global optimization approach that works on all objects and frames at once. To achieve practicality and scalability, we employ a divide and conquer formulation, thanks to which the computational complexity of the problem is reduced by orders of magnitude. We tested our algorithm with synthetic data, with experimental data of bird flocks and insect swarms and with public benchmark datasets, and show that our system yields high quality trajectories for hundreds of moving targets with severe overlap. The results obtained on very heterogeneous data show the potential applicability of our method to the most diverse experimental situations.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Attanasi
authors.forename: Andrea
authors.initials: A
authors.lastname: Cavagna
authors.forename: Lorenzo Del
authors.initials: LD
authors.lastname: Castello
authors.forename: Irene
authors.initials: I
authors.lastname: Giardina
authors.forename: Asja
authors.initials: A
authors.lastname: Jelic
authors.forename: Stefania
authors.initials: S
authors.lastname: Melillo
authors.forename: Leonardo
authors.initials: L
authors.lastname: Parisi
authors.forename: Fabio
authors.initials: F
authors.lastname: Pellacini
authors.forename: Edward
authors.initials: E
authors.lastname: Shen
authors.forename: Edmondo
authors.initials: E
authors.lastname: Silvestri
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Viale
mesh_terms: D000465:Algorithms; D000818:Animals; D001717:Birds; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007313:Insecta; D000069550:Machine Learning; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013382:Subtraction Technique; D051598:Whole Body Imaging / Q000379:methods*