兩種方法實作動态軌迹

在GIS中，動态軌迹的實作是非常有用的，可用GPS定位，熱點跟蹤等。在本例中，先建立一個用于呈現動态軌迹的臨時圖層，并在圖層上添加一個點表示位體的位置。代碼如下：

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代碼:

/** <summary>

/// 建立動态軌迹圖層

/// 2008年8月7日

/// <param name="trackLayerTableName">圖層表名</param>

/// <param name="trackLayerName">圖層名</param>

/// <param name="firstPoint">點初始坐标</param>

/// </summary>

protected void CreateTrackLayer(string trackLayerTableName, string trackLayerName, DPoint firstPoint)

{

MapInfo.Mapping.Map myMap = MapInfo.Engine.Session.Current.MapFactory[MapControl1.MapAlias];

//建立臨時圖層

MapInfo.Data.TableInfoMemTable tblInfoTemp = new MapInfo.Data.TableInfoMemTable(trackLayerTableName);

MapInfo.Data.Table tblTemp = MapInfo.Engine.Session.Current.Catalog.GetTable(trackLayerTableName);

if (tblTemp != null)

{

MapInfo.Engine.Session.Current.Catalog.CloseTable(trackLayerTableName);

}

tblInfoTemp.Columns.Add(MapInfo.Data.ColumnFactory.CreateFeatureGeometryColumn(myMap.GetDisplayCoordSys()));

tblInfoTemp.Columns.Add(MapInfo.Data.ColumnFactory.CreateStyleColumn());

tblTemp = MapInfo.Engine.Session.Current.Catalog.CreateTable(tblInfoTemp);

FeatureLayer workLayer = new FeatureLayer(tblTemp, AnimationLayerName, AnimationLayerName);

myMap.Layers.Add(workLayer);

//向臨時圖層中添加初始點

FeatureGeometry pfg = new MapInfo.Geometry.Point(workLayer.CoordSys, firstPoint.x, firstPoint.y) as FeatureGeometry;

MapInfo.Styles.CompositeStyle cstyle = new MapInfo.Styles.CompositeStyle(new MapInfo.Styles.SimpleVectorPointStyle(52, System.Drawing.Color.Blue, 30));

MapInfo.Data.Feature pft = new MapInfo.Data.Feature(tblTemp.TableInfo.Columns);

pft.Geometry = pfg;

pft.Style = cstyle;

workLayer.Table.InsertFeature(pft);

}

實作動态軌迹的第一種方法是，對原來點的坐标的位置進行偏移，從實作位置的更新。代碼如下：

/** <summary>

/// 把原來的點偏移到新的位置以實作動态軌迹

/// Glacier

/// 2008年8月7日

/// <param name="trackLayerTableName">圖層表名</param>

/// <param name="newPoint">點的新坐标</param>

/// </summary>

protected void UpdateTrack(string trackLayerTableName, DPoint newPoint)

{

MapInfo.Data.Table altb = MapInfo.Engine.Session.Current.Catalog.GetTable(trackLayerTableName);

if (altb == null)

{

return;

}

//Change the positon of the existed feature.

SearchInfo si = MapInfo.Data.SearchInfoFactory.SearchWhere("");

Feature ftr = MapInfo.Engine.Session.Current.Catalog.SearchForFeature(altb, si);

if (ftr == null)

{

return;

}

DPoint offsetPoint = new DPoint(newPoint.x - ftr.Geometry.Centroid.x, newPoint.y - ftr.Geometry.Centroid.y);

ftr.Geometry.GetGeometryEditor().OffsetByXY(offsetPoint.x, offsetPoint.y, DistanceUnit.Degree, DistanceType.Spherical);

ftr.Geometry.EditingComplete();

ftr.Update();

}

實作動态軌迹的第二種方法是，先删除原有的點，再在新的位置添加一個新點。因為第一種方法求偏移過程中可能會産生誤差，并且這種誤差是會積累的。而這種方法相對來說會比較精确一點。代碼如下：

/** <summary>

/// 把删除原有點并向圖層中添加新點以實作動态軌迹

/// Glacier

/// 2008年8月7日

/// <param name="trackLayerTableName">圖層表名</param>

/// <param name="newPoint">點的新坐标</param>

/// </summary>

protected void UpdateTrack(string trackLayerTableName, DPoint newPoint)

{

MapInfo.Data.Table altb = MapInfo.Engine.Session.Current.Catalog.GetTable(trackLayerTableName);

if (altb == null)

{

return;

}

//Delete the existed feature and create a new one.

SearchInfo si = MapInfo.Data.SearchInfoFactory.SearchWhere("");

Feature dftr = MapInfo.Engine.Session.Current.Catalog.SearchForFeature(altb, si);

if (dftr == null)

{

return;

}

altb.DeleteFeature(dftr);

MapInfo.Mapping.Map myMap = MapInfo.Engine.Session.Current.MapFactory[MapControl1.MapAlias];

FeatureGeometry pfg = new MapInfo.Geometry.Point(myMap.GetDisplayCoordSys(), new DPoint(newPoint.x, newPoint.y)) as FeatureGeometry;

MapInfo.Styles.CompositeStyle cstyle = new MapInfo.Styles.CompositeStyle(new MapInfo.Styles.SimpleVectorPointStyle(52, System.Drawing.Color.Blue, 30));

MapInfo.Data.Feature pft = new MapInfo.Data.Feature(altb.TableInfo.Columns);

pft.Geometry = pfg;

pft.Style = cstyle;

altb.InsertFeature(pft);

}