在Android中根据经度和纬度获取高度 [英] Get altitude by longitude and latitude in Android

问题描述

海拔应用程序屏幕http://img509.imageshack.us/img509/4848/elevationc.jpg

我的方法是使用 USGS海拔查询网络服务：

  private double getAltitude（Double Longitude，Double latitude）{
 double结果= Double.NaN; 
 HttpClient httpClient = new DefaultHttpClient（）; 
 HttpContext localContext = new BasicHttpContext（）; 
 String url =http://gisdata.usgs.gov/
 +xmlwebservices2 / elevation_service.asmx /
 +getElevation？X_Value =+ String.valueOf（longitude） 
 +& Y_Value =+ String.valueOf（latitude）
 +& Elevation_Units = METERS& Source_Layer = -1& Elevation_Only = true; 
 HttpGet httpGet = new HttpGet（url）; 
尝试{
 HttpResponse response = httpClient.execute（httpGet，localContext）; 
 HttpEntity entity = response.getEntity（）; 
 if（entity！= null）{
 InputStream instream = entity.getContent（）; 
 int r = -1; 
 StringBuffer respStr = new StringBuffer（）; （（r = instream.read（））！= -1）
 
 respStr.append（（char）r）; 
字符串tagOpen =< double>; 
字符串tagClose =< / double>; 
 if（respStr.indexOf（tagOpen）！= -1）{
 int start = respStr.indexOf（tagOpen）+ tagOpen.length（）; 
 int end = respStr.indexOf（tagClose）; 
字符串值= respStr.substring（start，end）; 
 result = Double.parseDouble（value）; 
} 
 instream.close（）; 
} 
} catch（ClientProtocolException e）{} 
 catch（IOException e）{} 
 return result; 
} 
  

使用示例（在

 
 
  public void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.main）; 
 linearLayout =（LinearLayout）findViewById（R.id.zoomview）; 
 mapView =（MapView）findViewById（R.id.mapview）; 
 mZoom =（ZoomControls）mapView.getZoomControls（）; 
 linearLayout.addView（mZoom）; 
 mapView.setOnTouchListener（new OnTouchListener（）{
 public boolean onTouch（View v，MotionEvent event）{$ b $ if（event.getAction（）== 1）{
 final GeoPoint p = mapView.getProjection（）。fromPixels（
（int）event.getX（），（int）event.getY（））; 
 final StringBuilder msg = new StringBuilder（）; 
 new Thread（new Runnable（）{
 public void run（）{
 final double lon = p.getLongitudeE6（）/ 1E6; 
 final double lat = p.getLatitudeE6（）/ 1E6; 
 final double alt = getAltitude（lon，lat）; 
 msg.append（Lon：）; 
 msg.append（lon）; 
 msg.append（Lat ：）; 
 msg.append（lat）; 
 msg.append（Alt ：）; 
 msg.append（alt）; 
} 
}）。run（）; 
 Toast.makeText（getBaseContext（），msg，Toast.LENGTH_SHORT）
 .show（）; 
} 
返回false; 
} 
}）; 
} 
  

Is there a quick and efficient way to get altitude (elevation) by longitude and latitude on the Android platform?

解决方案

elevation app screen http://img509.imageshack.us/img509/4848/elevationc.jpg

My approach is to use USGS Elevation Query Web Service:

private double getAltitude(Double longitude, Double latitude) {
    double result = Double.NaN;
    HttpClient httpClient = new DefaultHttpClient();
    HttpContext localContext = new BasicHttpContext();
    String url = "http://gisdata.usgs.gov/"
            + "xmlwebservices2/elevation_service.asmx/"
            + "getElevation?X_Value=" + String.valueOf(longitude)
            + "&Y_Value=" + String.valueOf(latitude)
            + "&Elevation_Units=METERS&Source_Layer=-1&Elevation_Only=true";
    HttpGet httpGet = new HttpGet(url);
    try {
        HttpResponse response = httpClient.execute(httpGet, localContext);
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            InputStream instream = entity.getContent();
            int r = -1;
            StringBuffer respStr = new StringBuffer();
            while ((r = instream.read()) != -1)
                respStr.append((char) r);
            String tagOpen = "<double>";
            String tagClose = "</double>";
            if (respStr.indexOf(tagOpen) != -1) {
                int start = respStr.indexOf(tagOpen) + tagOpen.length();
                int end = respStr.indexOf(tagClose);
                String value = respStr.substring(start, end);
                result = Double.parseDouble(value);
            }
            instream.close();
        }
    } catch (ClientProtocolException e) {} 
    catch (IOException e) {}
    return result;
}

And example of use (right in HelloMapView class):

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        linearLayout = (LinearLayout) findViewById(R.id.zoomview);
        mapView = (MapView) findViewById(R.id.mapview);
        mZoom = (ZoomControls) mapView.getZoomControls();
        linearLayout.addView(mZoom);
        mapView.setOnTouchListener(new OnTouchListener() {
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == 1) {
                    final GeoPoint p = mapView.getProjection().fromPixels(
                            (int) event.getX(), (int) event.getY());
                    final StringBuilder msg = new StringBuilder();
                    new Thread(new Runnable() {
                        public void run() {
                            final double lon = p.getLongitudeE6() / 1E6;
                            final double lat = p.getLatitudeE6() / 1E6;
                            final double alt = getAltitude(lon, lat);
                            msg.append("Lon: ");
                            msg.append(lon);
                            msg.append(" Lat: ");
                            msg.append(lat);
                            msg.append(" Alt: ");
                            msg.append(alt);
                        }
                    }).run();
                    Toast.makeText(getBaseContext(), msg, Toast.LENGTH_SHORT)
                            .show();
                }
                return false;
            }
        });
    }

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