/**
 * The Earth's tilt, degrees: the IAU's obliquity of the ecliptic at J2000. The tropics lie at this latitude, the polar circles at 90 degrees less it.
 *
 * @example
 * ```ts
 * import { EARTH_TILT } from "@johnmorrisdotca/chikyu-earth/realistic";
 *
 * console.log(EARTH_TILT, 90 - EARTH_TILT);
 * ```
 */
export declare const EARTH_TILT = 23.4393;
/**
 * The Earth's radius on the screen, in CSS pixels, from which the grid has a line every 15 degrees; below it, every 30.
 *
 * @example
 * ```ts
 * import { GRID_FINE_RADIUS } from "@johnmorrisdotca/chikyu-earth/realistic";
 *
 * console.log(GRID_FINE_RADIUS);
 * ```
 */
export declare const GRID_FINE_RADIUS = 220;
/**
 * The attributes the grid reads: `grid`.
 *
 * @example
 * ```ts
 * import { GRID_ATTRIBUTES } from "@johnmorrisdotca/chikyu-earth/realistic";
 *
 * console.log(GRID_ATTRIBUTES.join(" "));
 * ```
 */
export declare const GRID_ATTRIBUTES: readonly ["grid"];
/**
 * A `grid` attribute: absent (or `off`) draws none, anything else draws it.
 *
 * @param value - The attribute's text, or `null` when it is not there.
 * @returns Whether the grid is drawn.
 *
 * @example
 * ```ts
 * import { readGrid } from "@johnmorrisdotca/chikyu-earth/realistic";
 *
 * console.log(readGrid(null), readGrid(""), readGrid("off"));
 * ```
 */
export declare function readGrid(value: string | null): boolean;
/**
 * The grid's lines, ready for one batch of line segments: the special lines first, then the lines every 30 degrees, then the ones every 15 degrees in between, so that the first `coarse` points are
 * the grid of a small Earth and all `points` the grid of a large one.
 *
 * @example
 * ```ts
 * import { gridLines, type GridLines } from "@johnmorrisdotca/chikyu-earth/realistic";
 *
 * const grid: GridLines = gridLines();
 * console.log(grid.coarse < grid.points);
 * ```
 */
export interface GridLines {
    /** x, y, z of each point, two points to a segment. */
    positions: Float32Array;
    /** r, g, b of each point (0 to 255). */
    colours: Uint8Array;
    /** How many points the special lines and the 30-degree lines take. */
    coarse: number;
    /** How many points there are in all. */
    points: number;
}
/**
 * Makes the grid: meridians and parallels every 15 degrees (the parallels from 75 south to 75 north, the meridians to the poles), the equator brightest, the tropics and polar circles bright,
 * the prime meridian in a warm colour. Each line is cut into pieces of at most `step` degrees so it keeps to the sphere.
 *
 * @param step - The longest piece, in degrees (3 when left out).
 * @returns The segments and their colours.
 *
 * @example
 * ```ts
 * import { gridLines } from "@johnmorrisdotca/chikyu-earth/realistic";
 *
 * const grid = gridLines();
 * console.log(grid.points / 2, grid.coarse / 2);
 * ```
 */
export declare function gridLines(step?: number): GridLines;