java 通过经纬度获取海拔高度 百度地图api

可以使用百度地图的Elevation API来获取经纬度对应的海拔高度。以下是Java代码示例：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

public class ElevationAPI {
    public static void main(String[] args) throws Exception {
        String ak = "你的百度地图AK";
        double lat = 39.915;
        double lng = 116.404;
        int coordType = 3; // 坐标类型，3代表WGS84坐标系

        String url = "http://api.map.baidu.com/geoconv/v1/?coords=" + lng + "," + lat +
                "&from=" + coordType + "&to=6&ak=" + ak;
        String json = httpRequest(url);

        // 解析返回的json数据
        String status = getValueByKey(json, "status");
        if ("0".equals(status)) {
            String x = getValueByKey(json, "x");
            String y = getValueByKey(json, "y");

            // 获取海拔高度
            url = "http://api.map.baidu.com/elevation/v1/?locations=" + y + "," + x + "&coordtype=wgs84&ak=" + ak;
            json = httpRequest(url);
            status = getValueByKey(json, "status");
            if ("0".equals(status)) {
                String elevation = getValueByKey(json, "elevation");
                System.out.println("海拔高度：" + elevation);
            } else {
                System.out.println("获取海拔高度失败，错误码：" + status);
            }
        } else {
            System.out.println("坐标转换失败，错误码：" + status);
        }
    }

    public static String httpRequest(String requestUrl) throws IOException {
        StringBuilder sb = new StringBuilder();
        URL url = new URL(requestUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.setConnectTimeout(5000);
        connection.setReadTimeout(5000);

        InputStream inputStream = connection.getInputStream();
        InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

        String str;
        while ((str = bufferedReader.readLine()) != null) {
            sb.append(str);
        }

        bufferedReader.close();
        inputStreamReader.close();
        inputStream.close();
        connection.disconnect();

        return sb.toString();
    }

    public static String getValueByKey(String json, String key) {
        String value = "";
        int index = json.indexOf(key);
        if (index > 0) {
            index += key.length() + 2;
            boolean flag = true;
            while (flag) {
                String tmp = json.substring(index, index + 1);
                if (!",".equals(tmp) && !"}".equals(tmp)) {
                    value += tmp;
                    index++;
                } else {
                    flag = false;
                }
            }
        }
        return value;
    }
}

其中，ak是你的百度地图API Key，lat和lng分别是经纬度，coordType是坐标类型，这里使用的是WGS84坐标系。在代码中，先使用Geoconv API将经纬度转换为百度坐标系的x、y坐标，然后再使用Elevation API获取海拔高度。最后输出海拔高度即可。