/**
 * Bulk terrain heightfield (spec item C2 / "Elevation profile" — the shared
 * infrastructure both reference, "sampling shares C2's bulk heightfield, not
 * per-point elevationAt()"). `terrain-sample.ts`'s `sampleTerrainElevation`
 * is one fetch per point — fine for volume mode's handful of footprint
 * vertices, but the wrong shape for a profile's tens-to-hundreds of samples
 * along a line or the volumetrics grid's 10⁵–10⁶ cells: nearby points share
 * DEM tiles, so fetching (and decoding) each tile once and reading every
 * point out of it in memory is both fewer round-trips and what the per-cell
 * volume integrator (volumetrics.ts) builds on.
 *
 * This module is the DOM-TOUCHING half (fetch + canvas decode); the pixel
 * math — bilinear sampling with tile-seam handling — lives in
 * volumetrics.ts's `sampleBilinear`, which is pure and shared with the
 * volumetrics worker (decoded tiles postMessage across; canvases don't).
 */
import type { LngLat } from "./geodesy";
import type { TerrainIR } from "./terrain";
import { type HeightfieldTiles } from "./volumetrics";
/** A resolved, in-memory set of DEM tiles — `elevationAt` never touches the network. */
export interface TerrainHeightfield {
    /** Ground elevation (meters) at `lngLat` — bilinear-interpolated, seam-correct — or `null` if no covering tile loaded/decoded. Ignores `terrain.exaggeration`, same as `sampleTerrainElevation`. */
    elevationAt(lngLat: LngLat): number | null;
    /** The raw decoded tile set — the transferable form volumetrics.ts (and its worker) consume directly. */
    tiles: HeightfieldTiles;
}
/**
 * Resolves every DEM tile `points` touches — INCLUDING the neighbor tiles a
 * bilinear read at a tile-edge point spills into (the seam case: a point
 * within half a pixel of a tile border reads up to 3 pixels from adjacent
 * tiles; without pre-loading those, edge points would silently degrade to
 * fewer-corner interpolation) — fetches + decodes each ONE TIME
 * (deduplicated, in parallel), and returns a synchronous bilinear lookup. A
 * tile that fails to load makes points inside it resolve to `null` (same
 * "treat as no terrain" contract as `sampleTerrainElevation`) without
 * affecting other tiles.
 */
export declare function loadHeightfield(points: LngLat[], terrain: TerrainIR): Promise<TerrainHeightfield>;
/**
 * Resolves the DEM tile set COVERING a lng/lat bounding box — the
 * volumetrics grid's shape of demand ("every cell inside the polygon's
 * bbox"), which a point list can't express without enumerating 10⁶ cells.
 * Starts at the provider's `maxZoom` and steps down until the cover fits
 * `MAX_BOUNDS_TILES` — the returned `tiles.zoom` records what was actually
 * used, and the integrator derives its GSD (and error model) from that, so
 * a coarsened cover is REPORTED coarser, never silently pretended finer.
 */
export declare function loadHeightfieldForBounds(bounds: {
    west: number;
    south: number;
    east: number;
    north: number;
}, terrain: TerrainIR): Promise<TerrainHeightfield>;