LabordeObliqueMercatorProjection Class
A map projection for Madagascar.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public class LabordeObliqueMercatorProjection : ProjectionRemarks
Jean Laborde constructed formulas for an oblique Mercator projection, which was adopted for Madagascar in 1926. It is still the legal projection for Madagascar, but the projection formulas have not been used elsewhere, since they are regarded as inferior to the oblique Mercator formulas developed by Martin Hotine in the 1940s.
The scale is approximately true along a central oblique line, which is approximately a great circle (geodetic route), and which follows the general direction of Madagascar.
Our implementation becomes inaccurate far from Madagascar, so the projection should not be used outside its Area of Use. We have measured the "roundtrip error", by comparing a projected point p with the result of a roundtrip, the result of converting p to longitude/latitude and back again. The roundtrip error should of course be zero for an accurate map projection, but the map below shows that our Laborde implementation is not accurate everywhere.
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The roundtrip error is less than 1 cm on Madagascar itself, but increases rapidly offshore. The worst error in the Area of Use occurs in the southeast corner and is about 3 meters. We believe that it is the inverse direction (from projected coordinates back to LongLat) that is inaccurate.
To lower the risk of strange behavior, Carmenta has limited the extent of the projection. (The image above was created before the limitation was implemented.) However, to enjoy full safety from the limited extent, you must insert a RectangleClipOperator to the left of a DataSet, whenever the view uses the Laborde projection and the dataset does not.
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
ResourceObject
Projection
LabordeObliqueMercatorProjection
Platforms
Windows, Linux, Android
LabordeObliqueMercatorProjection Members
The LabordeObliqueMercatorProjection type has the following members.
Constructors
| Name | Description |
|---|---|
| LabordeObliqueMercatorProjection | Creates a new instance of the Laborde Oblique Mercator projection. |
Properties
| Name | Description |
|---|---|
| Authority | Gets the name of an authority, which is often "epsg". Inherited from Projection |
| AuthorityCode | Gets the unique code for the projection instance, according to the Authority, for example "19883". Inherited from Projection |
| Azimuth | The azimuth of the central line at the central point, clockwise from north. |
| CentralLatitude | The central latitude, also known as latitude of origin. |
| CentralLongitude | The central longitude, also known as central meridian or longitude of origin. |
| FalseEasting | Offset for the x coordinates. |
| FalseNorthing | Offset for the y coordinates. |
| IsDisposed | Gets a value that tells whether the current LabordeObliqueMercatorProjection has been disposed. Inherited from EngineObject |
| LengthUnit | The length unit of the projected coordinates. |
 LongLat | Gets a pre-defined LongLatProjection instance. Inherited from Projection |
| Name | Gets or sets the name of the LabordeObliqueMercatorProjection. Inherited from ResourceObject |
| NativeHandle | Gets the native Carmenta Engine kernel object the current LabordeObliqueMercatorProjection represents. Inherited from EngineObject |
| ScaleFactor | A scale factor, by which all projected coordinates will be multiplied. |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
Methods
| Name | Description |
|---|---|
| Clone | Creates a copy of an object. Inherited from EngineObject |
| Dispose | Releases the reference to the native Carmenta Engine kernel instance the EngineObject represents. Inherited from EngineObject |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| Utm | Returns one of the 120 predefined instances of Universal Transverse Mercator. Inherited from Projection |