index.c

/*
 * Copyright 2017, 2020-2021 Uber Technologies, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * Example program that converts coordinates to an H3 index (hexagon),
 * and then finds the vertices and center coordinates of the index.
 */

#include <h3/h3api.h>
#include <inttypes.h>
#include <stdio.h>

int main(int argc, char *argv[]) {
    // Get the H3 index of some location and print it.
    LatLng location;
    location.lat = degsToRads(40.689167);
    location.lng = degsToRads(-74.044444);
    int resolution = 10;
    H3Index indexed;
    if (latLngToCell(&location, resolution, &indexed) != E_SUCCESS) {
        printf("Failed\n");
        return 1;
    }
    printf("The index is: %" PRIx64 "\n", indexed);

    // Get the vertices of the H3 index.
    CellBoundary boundary;
    if (cellToBoundary(indexed, &boundary) != E_SUCCESS) {
        printf("Failed\n");
        return 1;
    }
    // Indexes can have different number of vertices under some cases,
    // which is why boundary.numVerts is needed.
    for (int v = 0; v < boundary.numVerts; v++) {
        printf("Boundary vertex #%d: %lf, %lf\n", v,
               radsToDegs(boundary.verts[v].lat),
               radsToDegs(boundary.verts[v].lng));
    }

    // Get the center coordinates.
    LatLng center;
    if (cellToLatLng(indexed, &center) != E_SUCCESS) {
        printf("Failed\n");
        return 1;
    }
    printf("Center coordinates: %lf, %lf\n", radsToDegs(center.lat),
           radsToDegs(center.lng));
}