我使用https://stackoverflow.com/a/5672274/6881568来查找海拔。我正在传递使用 GPS 获得的经度和纬度值（代码如下）
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
double altitude;
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
public GPSTracker(Context context) {
this.mContext = context;
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
// First get location from Network Provider
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
altitude = getAltitude(latitude,longitude);
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
altitude = getAltitude(latitude,longitude);
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
public double getLatitude(){
if(location != null){
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude(){
if(location != null){
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* */
public void showSettingsAlert(){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// Setting Icon to Dialog
//alertDialog.setIcon(R.drawable.delete);
// On pressing Settings button
alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
public double getAltitude(Double longitude, Double latitude) {
double result = Double.NaN;
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
String url = "https://maps.googleapis.com/maps/api/elevation/"
+ "xml?locations=" + String.valueOf(longitude)
+ "," + String.valueOf(latitude)
+ "&key=AIzaSyD4915zh6cSIB7BAUQI_WZWb-7EOjui8wg";
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 = "<elevation>";
String tagClose = "</elevation>";
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) (Double.parseDouble(value) *3.2808399);// convert from meters to feet
}
instream.close();
}
} catch (ClientProtocolException e) {
} catch (IOException e) {
}
return result;
}
当我在大楼的不同楼层进行如下测试时，我得到了错误的结果，
AT 5 楼 -（纬度 = 12.9174253，经度 = 77.5005331，海拔 = 2636.495278941856 英尺）
AT 4楼-（纬度=12.9176438，经度=77.5004883，海拔=2634.1930440302203英尺）
AT 3楼-（纬度=12.9175136，经度=77.5005331，海拔=2635.651439701728英尺）
这是错误的，我在第 3 级得到 2635，在第 4 级得到 2634。第四层的高度应该更高。在第二层我又得到了 2636 英尺