1  概述

通过ArcGIS Runtime for WindowsPhone SDK开发手机地图应用，能够定位所在位置，并将多个定位位置信息导出为GPX文件，供其他软件，如ArcMap、Google Earth等调用。本文将介绍如何实现地图定位，以及导出GPX文件的功能。

2  GeoCoordinateWatcher

Windows Phone SDK提供了GeoCoordinateWatcher类实现定位相关功能，需要引入System.Device.dll库，添加System.Device.Location命名空间。

2.1 参数设置

使用GeoCoordinateWatcher，需要创建一个实例，并设置定位精度、移动间距等基本属性，另外监听状态变化、结果变化等事件。如下代码所示：

if (_watcher == null)
{
    _watcher = new GeoCoordinateWatcher(GeoPositionAccuracy.High); // 使用高定位精度                
    _watcher.MovementThreshold = 50; // 最小移动间距，单位米，大于该间距的点才会触发PositionChanged事件
    _watcher.StatusChanged += new EventHandler<GeoPositionStatusChangedEventArgs>(watcher_StatusChanged);
    _watcher.PositionChanged += new EventHandler<GeoPositionChangedEventArgs<GeoCoordinate>>(watcher_PositionChanged);
}

2.2 启动定位

启动定位功能，即调用GeoCoordinateWatcher的Start方法，如下：

_watcher.Start();

2.3 定位状态

监听定位状态变化事件，如果出错可提示用户，如下：

void watcher_StatusChanged(object sender, GeoPositionStatusChangedEventArgs e)
{
    switch (e.Status)
    {
        case GeoPositionStatus.Disabled:                    
            if (_watcher.Permission == GeoPositionPermission.Denied)
            {            
                txtStatus.Text = "应用程序无权访问定位服务";
            }
            else
            {
                txtStatus.Text = "设备不支持定位服务";
            }
            break;
        case GeoPositionStatus.Initializing:                    
            break;
        case GeoPositionStatus.NoData:                    
            txtStatus.Text = "获取定位数据失败"; 
            break;
        case GeoPositionStatus.Ready:
            txtStatus.Text = "GPS已经就绪";
            break;
    }
}

2.4 定位结果

对定位结果的处理，需要在定位位置变化事件中进行，如下所示：

void watcher_PositionChanged(object sender, GeoPositionChangedEventArgs<GeoCoordinate> e)
{
            try
            {
                txtStatus.Text = "";

                MapPoint point = new MapPoint(e.Position.Location.Longitude, e.Position.Location.Latitude);
                ESRI.ArcGIS.Client.Projection.WebMercator mercator = new ESRI.ArcGIS.Client.Projection.WebMercator();
                MapPoint ptCurrent = mercator.FromGeographic(point) as MapPoint;

                //更新GPS定位点位置
                _gLocation.Geometry = ptCurrent;

                //更新轨迹线
                if (_gpsPoints == null)
                {
                    _gpsPoints = new PointCollection();
                    _gpsPoints.Add(ptCurrent);
                }
                else
                {
                    _gpsPoints.Add(ptCurrent);
                    Polyline line = new Polyline();
                    line.Paths.Add(_gpsPoints);
                    _gTrackLine.Geometry = line;
                }

                #region 记录GPS定位信息

                GpsInfo gpsInfo = new GpsInfo();
                gpsInfo.Altitude = e.Position.Location.Altitude;
                gpsInfo.Course = e.Position.Location.Course;
                gpsInfo.HorizontalAccuracy = e.Position.Location.HorizontalAccuracy;
                gpsInfo.Latitude = e.Position.Location.Latitude;
                gpsInfo.Longitude = e.Position.Location.Longitude;
                gpsInfo.Speed = e.Position.Location.Speed;
                gpsInfo.VerticalAccuracy = e.Position.Location.VerticalAccuracy;
                gpsInfo.Time = e.Position.Timestamp.DateTime;

                _gpxWriter.AddGpsInfo(gpsInfo);

                #endregion

                _gpsLayer.Re