Lat-Lon

Grid family
latlon
Kind
grid
Source
src/grids/latlon.jl
Tags
#grid #structured #spherical #lat-lon

Description

The lat-lon family is a regular mesh on the sphere of radius R indexed by longitude φ and latitude λ. Cells are bounded by meridians (constant φ) and parallels (constant λ); cell area shrinks toward the poles as R² cos λ dλ dφ. The metric tensor is diagonal with g_{φφ} = R² cos² λ and g_{λλ} = R², so finite-difference rules carry a cos λ factor on the longitudinal stencil (see centered_2nd_uniform_latlon).

Pole handling is configurable via the pole_policy knob — none (the default) leaves polar cells degenerate, while wrap-and-stitch policies live in the accessor.

Visualization

Lat-lon mesh in equirectangular projection
Lat-lon 24×12 mesh shown in equirectangular projection. Cell area is proportional to cos λ — visible in the spherical metric, not in this flat projection.

Trait coverage

Registered against AbstractCurvilinearGrid. Supplies the full bulk-array trait contract; metric_g / metric_ginv / metric_jacobian carry the spherical metric, which downstream rules consume directly.

Canonical fixtures

  • discretizations/grids/latlon/lat_lon_1deg.esm — 360×180 (1°)
  • discretizations/grids/latlon/lat_lon_0p25deg.esm — 1440×720 (0.25°)
  • discretizations/grids/latlon/lat_lon_0p1deg.esm — 3600×1800 (0.1°)

See also