EllipseOperator.MaxRadialEdgeLength Property
Gets or sets a value specifying the maximal length of a radial edge of a generated sector.
Syntax
public AttributeVariable< System.Double > MaxRadialEdgeLength { get; set; }Property Value
Default: max
The maximal length of a radial edge of a generated sector, in the length unit specified by RadiusUnit.
Remarks
If a sector is generated instead of a full circle or ellipse, then the two radial edges could be long. If you need the radial edges to trace great-circle routes with high accuracy, you may need them segmented into shorter edges, since a long great-circle route will in general not appear as a straight line in the View.Crs. (Actually, a gnomonic map projection would display great-circle routes on a spherical Earth as straight lines, but the gnomonic has many drawbacks and is not supported by Carmenta.)
This property gives the maximal length of a sub-segment along a radial edge. If the given value is less than 1 000 m, then 1 000 m will be used anyway, to avoid long processing times on very small values.
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The default value is huge, so it will not cause extra nodes to be inserted on the radial edges. This is because if the View.Crs is used in the central area of its map projection where projection distortions are small, then great-circle routes should appear very nearly straight, so extra nodes may be unnecessary. However, a common use case is that the view CRS has a MercatorProjection that is used also far from its central area (near the equator). In this case, a great-circle route that does not go due north or due south will deviate noticeably from a straight line, especially on higher latitudes.
For a Mercator view, the table below gives the maximal value of MaxRadialEdgeLength you can use on various latitudes to ensure that the apparent deviation from a great-circle route is less than 1 meter or less than 10 meters. At a given latitude, the worst deviation grows quadratically with the edge length.
latitude | 1 m tol. | 10 m tol. |
|---|---|---|
85° | 2 121 m | 6 692 m |
80° | 3 004 m | 9 500 m |
70° | 4 250 m | 13 648 m |
55° | 5 984 m | 18 923 m |
30° | 9 404 m | 29 740 m |
Platforms
Windows, Linux, Android