Graticule Map
Signature
sp.graticule_map(title, *, variant="lines", step=15, center_lat=None, center_lon=None, color_low=None, color_high=None, **kwargs) -> Chart
Aliases: sp.graticule_map, sp.graticulemap, sp.graticule_map_chart, sp.graticule, sp.meridian_map, sp.grid_map, sp.build_graticule_map
Description
sp.graticule_map() needs no data at all — it draws the coordinate reference grid itself: meridians and parallels every step degrees, the equator and prime meridian emphasized. No lats/lons/values because the grid is the content, the same way daynight needs none for its terminator. Useful on its own as a reference layer, or as a way to see exactly how this toolkit’s own projections behave.
Variants
Parameters
Returns
Chart — object with .html property and .show() method.
The default: a flat meridian/parallel grid drawn directly through this map’s own equirectangular-style projection, degree-labeled at the edges, equator and prime meridian drawn heavier than the rest.
The same grid wrapped onto a real sphere: every meridian and parallel is sampled and projected through the orthographic projection point by point, so each line genuinely curves and disappears past the limb exactly where a real globe’s would — not a flat grid pasted onto a circle. center_lat / center_lon aim the view (default 20, 10). Country outlines render on the sphere for context.
Tissot’s indicatrix, the classic cartographic honesty check: a small circle of genuinely fixed angular radius — the real spherical destination-point formula, not a drawn ellipse — is placed at every grid intersection and re-projected through this map’s own flat projection. Near the equator it stays close to circular; near the poles it visibly stretches, showing this toolkit’s actual distortion rather than asserting it.