Syntactic tracking aims to classify a target's spatiotemporal trajectory by using natural language processing models. This paper proposes constrained stochastic context free grammar (CSCFG) models for target trajectories confined to a roadmap. We present a particle filtering algorithm that exploits the CSCFG model structure to estimate the target's trajectory. This metalevel algorithm operates in conjunction with a base-level target tracking algorithm. Extensive numerical results using simulated ground moving target indicator (GMTI) radar measurements show useful improvement in both trajectory classification and target state (both coordinates and velocity) estimation.Keywords-syntactic tracking, constrained stochastic context free grammar (CSCFG), particle filter, Earley Stolcke parser 1 Traditionally, given track information, a radar (human) operator examines target trajectories to determine anomalous behavior. This paper develops natural language models and meta-level signal processing algorithms for estimating anomalous trajectories. Such "middleware" forms the interface between the physical signal processing layer and the radar operator; see also [7] for alternative models for intent using bridging distributions.