geohash.h

/*
 *  geohash.h
 *  libgeohash
 *
 *  Created by Derek Smith on 10/6/09.
 *  Copyright (c) 2010, SimpleGeo
 *	All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without 
 *  modification, are permitted provided that the following conditions are met:

 *  Redistributions of source code must retain the above copyright notice, this list
 *  of conditions and the following disclaimer. Redistributions in binary form must 
 *  reproduce the above copyright notice, this list of conditions and the following 
 *  disclaimer in the documentation and/or other materials provided with the distribution.
 *  Neither the name of the SimpleGeo nor the names of its contributors may be used
 *  to endorse or promote products derived from this software without specific prior 
 *  written permission. 
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
 *  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 
 *  THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 
 *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 
 *  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
 *  OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#define MAX_LAT             90.0
#define MIN_LAT             -90.0

#define MAX_LONG            180.0
#define MIN_LONG            -180.0

#define NORTH               0
#define EAST                1
#define SOUTH               2
#define WEST                3

#define MAX_PRECISION       12
#define MIN_PRECISION       1
#define DEF_PRECISION       6

#define LENGTH_OF_DEGREE	111100				// meters


// Metric in meters
typedef struct GeoBoxDimensionStruct {
	
	double height;
	double width;

} GeoBoxDimension;

typedef struct GeoCoordStruct {
    
    double latitude;
    double longitude;
    
    double north;
    double east;
    double south;
    double west;

	GeoBoxDimension dimension;
    
} GeoCoord;


/*
 * Creates a the hash at the specified precision. If precision is set to 0.
 * or less than it defaults to 12.
 */
extern char* geohash_encode(double lat, double lng, int precision);

/* 
 * Returns the latitude and longitude used to create the hash along with
 * the bounding box for the encoded coordinate.
 */
extern GeoCoord geohash_decode(char* hash);

/* 
 * Return an array of geohashes that represent the neighbors of the passed
 * in value. The neighbors are indexed as followed:
 *
 *                  N, NE, E, SE, S, SW, W, NW
 * 					0, 1,  2,  3, 4,  5, 6, 7
 */ 
extern char** geohash_neighbors(const char* hash);

extern void geohash_free_neighbors(char ** neighbors);
/*
 * Returns the width and height of a precision value.
 */
extern const GeoBoxDimension dimension_cache[];

extern GeoBoxDimension geohash_dimensions_for_precision(int precision);