/**
 * Geohash utilities for lightning strike location filtering
 * Based on the homeassistant-blitzortung implementation
 */
/**
 * Bounding box for geographic area
 */
export interface BoundingBox {
    minLat: number;
    minLon: number;
    maxLat: number;
    maxLon: number;
}
/**
 * Calculate bounding box around a point given a radius in kilometers
 * @param lat Latitude
 * @param lon Longitude
 * @param radiusKm Radius in kilometers
 * @returns Bounding box
 */
export declare function calculateBoundingBox(lat: number, lon: number, radiusKm: number): BoundingBox;
/**
 * Get all geohash neighbors for a given geohash
 * @param hash Geohash string
 * @returns Array of neighbor geohashes (up to 8 neighbors)
 */
export declare function getGeohashNeighbors(hash: string): string[];
/**
 * Compute geohash tiles that overlap a circular search area
 * Uses breadth-first search to find all geohashes within the bounding box
 * @param lat Center latitude
 * @param lon Center longitude
 * @param radiusKm Search radius in kilometers
 * @param precision Geohash precision (1-12)
 * @returns Set of geohash strings that overlap the search area
 */
export declare function computeGeohashTiles(lat: number, lon: number, radiusKm: number, precision: number): Set<string>;
/**
 * Calculate optimal geohash tiles for MQTT subscription
 * Selects the coarsest precision that keeps the tile count at or below maxTiles
 * This balances spatial granularity against subscription overhead
 *
 * @param lat Center latitude
 * @param lon Center longitude
 * @param radiusKm Search radius in kilometers
 * @param maxTiles Maximum number of tiles (default 9, as used by homeassistant-blitzortung)
 * @returns Set of geohash strings to subscribe to
 */
export declare function calculateGeohashSubscriptions(lat: number, lon: number, radiusKm: number, maxTiles?: number): Set<string>;
/**
 * Check if a point is within a radius of a center point
 * Uses Haversine formula for great-circle distance
 *
 * @param centerLat Center latitude
 * @param centerLon Center longitude
 * @param pointLat Point latitude
 * @param pointLon Point longitude
 * @param radiusKm Radius in kilometers
 * @returns true if point is within radius
 */
export declare function isWithinRadius(centerLat: number, centerLon: number, pointLat: number, pointLon: number, radiusKm: number): boolean;
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