Parametric objects refer to geometries represented by one or more parameters (such as angle, length, etc.) for (x,y) coordinate points, for example, circles and ellipses are expressed using parametric equations as follows:
Circle: x=a+rcosɵ, y=b+rsinɵ (ɵϵ[0,2л))
Ellipse: x=acosɵ, y=bsinɵ (ɵϵ[0,2л))
The advantage of using parametric objects to express the geometric features of features is that when there are curves in the contour lines of real-world features, using parametric data for description makes the map display more closely fit the actual feature contours and more accurate in geometric calculations such as area and perimeter.
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Figure Outline curve of the playground |
Parametric Object Types
Currently, parametric objects supported for storage in line and region datasets include circles, arcs, ellipses, elliptic arcs, and 3rd-order poly bezier curves, as well as composite lines and region datasets composed of these parametric objects. Specific parametric object types are described as follows:
Parametric Object
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Description
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Parametric Object Graphic
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Class Name
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Arc
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GeoArc
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Circle
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GeoCircle
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Elliptic arc
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GeoEllipticArc
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Ellipse
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GeoEllipse
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Poly bezier
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3rd-order poly bezier
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GeoBezier3Curve
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Parametric line
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Can consist of the following geometries: polyline (GeoLine), arc (GeoArc), circle (GeoCircle), elliptic arc (GeoEllipticArc), ellipse (GeoEllipse), poly bezier (GeoBezier3Curve), with the end coordinate of the previous geometry coinciding with the start coordinate of the next geometry.
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GeoCompoundCurv
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Parametric region
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Can consist of the following geometries: polyline (GeoLine), parametric line (GeoCompoundCurve), circle (GeoCircle), ellipse (GeoEllipse), with all geometries being closed.
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GeoCurvePolygon
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Parametric multiline
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Composed of multiple sub-objects, each containing only one geometry, which can be: polyline (GeoLine), arc (GeoArc), circle (GeoCircle), elliptic arc (GeoEllipticArc), ellipse (GeoEllipse), parametric line (GeoCompoundCurve), poly bezier (GeoBezier3Curve). Specifically, when the sub-object is GeoLine, the contained line object count must be 1.
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GeoMultiCurve
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Parametric multipolygon
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Composed of multiple sub-objects, each containing only one geometry, which can be: polygon (GeoRegion), parametric region (GeoCurvePolygon). Specifically, when the sub-object is GeoRegion, the contained polygon object count must be 1.
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GeoMultiSurface
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External Format Parametric Object Import
Currently supports importing parametric objects from DWG and FileGDB data, and parametric object import is supported in Windows_x86, Linux_x86, and Linux_arm environments.
- DWG
DWG GeometryImport as Line/Region DatasetImport as CAD DatasetKeep Parametric ObjectDo Not Keep Parametric ObjectKeep Parametric ObjectDo Not Keep Parametric ObjectCircle, ellipseCircle, ellipseFitted polyline/polygonCircle, ellipseCircle, ellipseArc, elliptic arcArc, elliptic arcFitted polylineArc, elliptic arcArc, elliptic arcSpline curveParametric lineFitted polylineParametric lineFitted polylinePolylineParametric lineFitted polylineParametric lineCompoundHatch patternParametric regionFitted polygonParametric regionCompoundBlockParametric line/polygonFitted polyline/polygonParametric line/polygonCompound
* When importing polylines as CAD datasets, "keep parametric object" must be set, and parametric objects must exist, ignoring polyline width or when polyline width is 0, to import as parametric objects; otherwise, they will be imported as compounds.
* When importing DWG as parametric objects, only 2D datasets are supported; if object height information is kept, it will be fitted to polylines.
- FileGDB
FileGDB GeometryImport Line/Region DatasetCircle, arcCircle, arcPoly bezierParametric multiline with sub-object as poly bezierCircle, ellipse, parametric regionCircle, ellipse, parametric regionLine/polygon features composed of multiple line/region geometries (see Figure 2)Parametric multiline/parametric multipolygon
* When a FileGDB line/polygon feature has multiple sub-objects (as shown below), import will convert it to a parametric multiline/parametric multipolygon containing multiple sub-objects.
Figure Parametric multiline composed of multiple sub-objects
- Other External Formats
Parametric objects in other external formats will be fitted to polylines upon import.
Parametric Object Export to External Formats
Currently, parametric objects are kept only when exporting to DWG or DXF formats, and this is supported in Windows_x86, Linux_x86, and Linux_arm environments. Exporting to other formats, including those that do not support parametric objects, such as CSV, GeoJSON, KML, etc., will fit parametric objects to polylines.
Function Support
- Current vector processing and analysis functions supporting parametric objects include: overlay analysis, buffer analysis, dissolve, regularize building, compute area, vector resampling, centerline from double lines, centerline from polygon, measure distance, smooth line/polygon, create random point, vector to raster, update attributes, edgematching, vector clip, line topology processing, eliminate, polygon aggregation, cluster and outlier analysis (Anselin Local Moran's I), hot spot analysis (Getis-Ord Gi*), etc.
- Starting from SuperMap iDesktopX 2025, supported feature editing functions for parametric objects include only: erase, line to point, polygon to line, line to polygon, specify coordinates, specify orientation, specify offset, positioning copy, mirror, rotate.
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