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 separate from the line segments of the set of polygons, 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, the open line segments for each interval comprising one or more line segments of the polygon intersected by a ray projected in the corresponding 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 causing display of 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.