The d3-geo module contains methods and functions for spherical math operations, which can compute areas and distances, find centroids and bounds of an object in spherical or planar coordinates. Operations in planar geometry occur in the viewport domain and use pixel coordinates. They are methods of the d3.geoPath() object. Corresponding operations in spherical geometry are top-level functions. They all operate on GeoJSON objects. The following table compares them:
|
Planar geometry |
Spherical geometry |
Description |
|
geoPath.area(object) |
d3.geoArea(object) |
Computes the area of a shape. The planar area() method computes a visible (non-clipped) area of the projected shape in square pixels. Different projections and aspects will result in different values. The spherical d3.geoArea() function computes the area in square radians (steradians), and is projection... |
