ProjectionBase Class
The base class for all projections used in the MapControl.
Namespace: DevExpress.Xpf.Map
Assembly: DevExpress.Xpf.Map.v24.2.dll
NuGet Package: DevExpress.Wpf.Map
Declaration
Related API Members
The following members return ProjectionBase objects:
Example
To create a custom projection, inherit the ProjectionBase
class and override the following methods of the base class.
- ProjectionBase.GeoPointToMapUnit - converts geographic points to internal map units.
- ProjectionBase.MapUnitToGeoPoint - converts internal map units to geographic points.
- ProjectionBase.GeoToKilometersSize - converts sizes in geographic units into the corresponding size in kilometers.
- ProjectionBase.KilometersToGeoSize - converts sizes in kilometers into the corresponding size in geographical units.
Imports DevExpress.Xpf.Map
Imports System
Imports System.Windows
Namespace CustomProjection
Friend Class HammerAitoffProjection
Inherits ProjectionBase
Public Overrides Property OffsetX() As Double
Get
Return 0.5
End Get
Set(value As Double)
End Set
End Property
Public Overrides Property OffsetY() As Double
Get
Return 0.5
End Get
Set(value As Double)
End Set
End Property
Public Overrides Property ScaleX() As Double
Get
Return 0.5
End Get
Set(value As Double)
End Set
End Property
Public Overrides Property ScaleY() As Double
Get
Return -0.25
End Get
Set(value As Double)
End Set
End Property
Private Const minLatitude As Double = -90.0
Private Const maxLatitude As Double = 90.0
Private Const minLongitude As Double = -180.0
Private Const maxLongitude As Double = 180.0
Private Shared Function RadianToDegree(ByVal value As Double) As Double
Return value * 180.0 / Math.PI
End Function
Private Shared Function DegreeToRadian(ByVal value As Double) As Double
Return value * Math.PI / 180.0
End Function
Private Function IsValidPoint(ByVal x As Double, ByVal y As Double) As Boolean
If Math.Pow(x, 2) + Math.Pow(y, 2) > 1 Then
Return False
End If
Return True
End Function
Public Overrides Function GeoPointToMapUnit(ByVal geoPoint As GeoPoint) As MapUnit
Dim lonInRadian As Double = DegreeToRadian(Math.Min(maxLongitude, Math.Max(minLongitude, geoPoint.Longitude)))
Dim latInRadian As Double = DegreeToRadian(Math.Min(maxLatitude, Math.Max(minLatitude, geoPoint.Latitude)))
Dim z As Double = Math.Sqrt(1 + Math.Cos(latInRadian) * Math.Cos(lonInRadian / 2))
Dim x As Double = Math.Cos(latInRadian) * Math.Sin(lonInRadian / 2) / z
Dim y As Double = Math.Sin(latInRadian) / z
Return New MapUnit(x * ScaleX + OffsetX, y * ScaleY + OffsetY)
End Function
Public Overrides Function MapUnitToGeoPoint(ByVal mapUnit As MapUnit) As GeoPoint
Dim x As Double = (mapUnit.X - OffsetX) / ScaleX
Dim y As Double = Math.Min(1, Math.Max(-1, (mapUnit.Y - OffsetY) / ScaleY))
If IsValidPoint(x, y) Then
Dim z As Double = Math.Sqrt(1 - 0.5 * Math.Pow(x, 2) - 0.5 * Math.Pow(y, 2))
Dim c As Double = Math.Sqrt(2) * z * x / (2 * Math.Pow(z, 2) - 1)
Dim lon As Double = 2 * Math.Atan(c)
Dim lat As Double = Math.Asin(Math.Min(Math.Max(Math.Sqrt(2) * z * y, -1), 1))
Dim latInDegree As Double = lat * maxLongitude / Math.PI
Dim lonInDegree As Double = lon * maxLongitude / Math.PI
Return New GeoPoint(Math.Min(maxLatitude, Math.Max(minLatitude, RadianToDegree(lat))), Math.Min(maxLongitude, Math.Max(minLongitude, RadianToDegree(lon))))
Else
Dim signX As Integer = If(x < 0, -1, 1)
Dim signY As Integer = If(y < 0, -1, 1)
Return New GeoPoint(maxLatitude * signY, maxLongitude * signX)
End If
End Function
Public Overrides Function GeoToKilometersSize(ByVal anchorPoint As GeoPoint, ByVal size As Size) As Size
Return New Size(size.Width * LonToKilometersRatio * Math.Cos(DegreeToRadian(anchorPoint.Latitude)), size.Height * LatToKilometersRatio)
End Function
Public Overrides Function KilometersToGeoSize(ByVal anchorPoint As GeoPoint, ByVal size As Size) As Size
Return New Size(size.Width / LonToKilometersRatio / Math.Cos(DegreeToRadian(anchorPoint.Latitude)), size.Height / LatToKilometersRatio)
End Function
End Class
End Namespace
Inheritance
Object
ProjectionBase
See Also