1. A computer-implemented method, comprising: accessing video data for a geographic area captured by a video camera; processing the video data to detect a plurality of moving vehicles in the video data; defining a detection area based on the plurality of moving vehicles; extracting a plurality of line segments for each of the plurality of vehicles detected in the video data; estimating a plurality of vanishing points based on at least a subset of the plurality of line segments; and determining a camera calibration based on the plurality of vanishing points, wherein extracting a plurality of line segments includes: detecting a plurality of edges of one of the plurality of vehicles within the detection area; and identifying straight line segments within the detection area.