本文介绍了在Android中通过经度和纬度获取高度的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
Android平台上有没有快速有效的通过经纬度获取高度(海拔)的方法?
Is there a quick and efficient way to get altitude (elevation) by longitude and latitude on the Android platform?
推荐答案
我的方法是使用 USGS 海拔查询网络服务:
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;
}
和使用示例(就在 HelloMapView 类中):
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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