KrovakNorthOrientedProjection Class
A map projection also known Krovak Oblique Conformal Conic.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public class KrovakNorthOrientedProjection : ProjectionRemarks
This map projection is an oblique version of the Lambert conformal conic projection. It was invented by Josef Křovák in the 1920s for conformal mapping of Czechoslovakia with minimal scale variation. He noted that the country was long and narrow along a small circle centered near Helsinki. So he placed his cone apex at the circle center. The cone is then cut along the line that goes north from the apex.
The projection formulas use an ellipsoid model of the Earth.
 |
The Krovak projection is still used in the Czech and Slovakian republics, but the projection type has not been used elsewhere. So, the term "Krovak projection" usually refers to the usage in Czech-and-Slovakia, rather than to an arbitrary instance of the projection type.
For the record, though, a recent mapping proposal appears to be a reinvention of the Krovak projection, plus a final rotation of the projected coordinates. (P. Vanicek and M. Najafi-Alamdari, Proposed new cartographic mapping for Iran. Spatial Science, Vol. 49, No. 2, 2004.) Also, there is the related Bipolar Oblique Conic Conformal Projection, tailor-made for the American continent by O. M. Miller and W. A. Briesemeister, which uses two oblique cones, and assumes that the Earth is spherical.
Axis direction in Krovak
In traditional paper cartography for the Czech and Slovakian republics, the first coordinate axis (X) goes south, and the second (Y) goes west, starting from the cone apex near Helsinki. As described by EPSG, axes that go south and west is a built-in feature of the general class of Krovak projections (EPSG name "Krovak", with coordinate operation method code 9819).
However, GIS users have had trouble with these axis directions, since some GIS and CAD software would show such maps with north down. So a north-oriented variant of the projection has been devised, with the axes going east and north, and this variant is in fact more common for GIS data. (EPSG name "Krovak (North Orientated)", with coordinate operation method code 1041, added to the EPSG database in November 2010.) To convert between the two variants, it is enough to negate the coordinates. (This means that in the north-oriented Krovak, all coordinates are negative in the Czech and Slovakian republics.)
 |
To simplify matters for GIS usage, the Krovak of Carmenta Engine is the north-oriented variant. To implement the south-oriented variant, you can negate the ScaleFactor. (This can be useful if a data file has coordinates expressed in the south-oriented variant).
Modified Krovak
In 2009, Czech authorities introduced a modified variant of the Krovak projection method. The new variant starts by computing projected coordinates just like the traditional Krovak, but then the coordinates are modified slightly by means of a specially designed polynomial.
The modified Krovak shall be used with a modified geodetic datum, S-JTSK/05, which covers the Czech republic only, instead of the traditional datum S-JTSK, which covers former Czechoslovakia.
The modified Krovak projection method was added to the EPSG database in November 2010, with coordinate operation method codes 1042 (south-oriented) and 1043 (north-oriented). The modified Krovak is not implemented by Carmenta, but as we understand it, the differences are less than a meter, and most Carmenta Engine users don't need sub-meter accuracy. So, to be able to support calling Crs.FromAuthorityAndCode("epsg","5224") to get the Crs "S-JTSK/05 (Ferro) / Modified Krovak" and calling Crs.FromAuthorityAndCode("epsg","5225") to get the Crs "S-JTSK/05 (Ferro) / Modified Krovak East North", we interpret the Modified Krovak as if it were the traditional one. We think this approach gives an approximation with better than meter accuracy, in theory. In practice, we get the additional effect that a HelmertDatumShift designed for S-JTSK/05 over the Czech republic is chosen, instead of one designed for S-JTSK over former Czechoslovakia. This effect, which amounts to a parallel translation of about 1.5 meters, should give a better datum shift inside the Czech republic.
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
ResourceObject
Projection
KrovakNorthOrientedProjection
Platforms
Windows, Linux, Android
KrovakNorthOrientedProjection Members
The KrovakNorthOrientedProjection type has the following members.
Constructors
| Name | Description |
|---|---|
| KrovakNorthOrientedProjection | Creates a new instance of the Krovak 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 |
| CentralLatitude | The central latitude. |
| CentralLongitude | The central longitude, also known as central meridian. |
| ColatitudeConeAxis | Tells how much the oblique cone axis has been tilted from the North pole. |
| FalseEasting | Offset for the x coordinates. |
| FalseNorthing | Offset for the y coordinates. |
| IsDisposed | Gets a value that tells whether the current KrovakNorthOrientedProjection 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 KrovakNorthOrientedProjection. Inherited from ResourceObject |
| NativeHandle | Gets the native Carmenta Engine kernel object the current KrovakNorthOrientedProjection represents. Inherited from EngineObject |
| PseudoStandardParallel | Latitude of pseudo standard parallel. |
| 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 |