1. A computer-implemented method for displaying geographic data, comprising: obtaining a set of polygons that define a set of geographic regions, wherein each polygon comprises line segments that define a border of the polygon, and wherein each line segment is defined by coordinates for two endpoints of the line segment; projecting rays from the endpoints of the line segments that comprise the set of polygons onto a reference line, wherein the rays are projected in a direction orthogonal to the reference line to form intersection points with the reference line; for each interval between pairs of consecutive intersection points on the reference line, keeping track of open line segments that project onto the interval; for each data point in a set of data points to be processed, identifying a relevant interval on the reference line that the data point projects onto, performing a crossing number (CN) operation by counting intersections between a ray projected from the data point and open line segments associated with the relevant interval to identify zero or more polygons that the data point falls into, and incrementing a count for each polygon that the data point falls into; and displaying the set of geographic regions, wherein each polygon that defines a geographic region is marked to indicate a number of data points that fall into the polygon.