Calculate Geometry Attributes

Feature Description

Calculate Geometry Attributes adds spatial or geometric attributes of vector objects as new property fields, such as center coordinates, subobject count, geodesic perimeter, etc. These attributes represent the object's own metadata properties.

When users need to utilize these attributes for operations and processing, they can directly add them as new property fields through this function without additional tools, significantly improving the efficiency of geographic spatial data processing. This function adds one or more property fields to the current attribute table, depending on the options specified in the Geometric Properties parameter. This operation modifies source data. Please backup data before proceeding if you wish to preserve original data.

Feature Entry

Attribute Table Tab->Edit Group->Calculate Geometry Attributes button, opens Calculate Geometry Attributes dialog.
Data Tab->Data Processing->Vector->Calculate Geometry Attributes.
Toolbox->Data Processing->Vector->Calculate Geometry Attributes.

Parameter Description

Geometric Properties: Supports calculating multiple fields' geometric properties simultaneously. Specify fields to store calculation results, either existing fields or new fields. Entering existing field names will overwrite current values; new field names will create fields to store results. Fields must correspond one-to-one with geometric properties. Available properties vary slightly depending on dataset type.
E.g., point datasets only offer X/Y coordinates; region datasets provide geodesic area, geodesic perimeter, etc.
- Center Coordinates (X/Y): Divided into CenterPointCoordinate_X and CenterPointCoordinate_Y attributes.
- Centroid Coordinates (X/Y): Divided into CentroidCoordinate_X and CentroidCoordinate_Y attributes.
- Geodesic Area: Adds geodesic area for region objects.
  Geodesic lines follow Earth's surface curvature. Geodesic area refers to curved surface measurements. For geographic coordinate systems, improved algorithms effectively reduce calculation deviations caused by Earth's curvature; For Gauss_Kruger (Xian 1980) and Gauss_Kruger (GCS2000) coordinate systems, precise spherical areas are calculated using inverse Gaussian coordinate formulas from "Third National Land Survey Technical Specifications"; Other projected and planar coordinate systems calculate planar areas directly.
  
  Note:
  
  Starting from SuperMap 11i (2024), the "Ellipsoidal Area" and "Geodesic Area" algorithms have been improved and integrated. The "Ellipsoidal Area" option has been removed. For more accurate results, use "Geodesic Area". Models configured with "Ellipsoidal Area" in previous versions will automatically switch to "Geodesic Area" when imported into the new version.
- Geodesic Perimeter: Adds geodesic perimeter for regions or geodesic length for lines.
  In geographic coordinate systems, geodesic perimeter matches default SmPerimeter in ellipsoidal space. For projected/planar coordinate systems, specify geographic coordinate system to calculate meaningful geodesic perimeter, as default SmPerimeter represents planar measurements.
- Subobject Count: Adds count of subobjects contained in objects.
- Node Count: Adds node count for line/region objects.
- Bound Coordinates: Includes four attributes for max/min x/y coordinates.
- Line Start Point: Divided into LineStartPoint_X and LineStartPoint_Y attributes.
- Line Midpoint: Divided into LineCenterPoint_X and LineCenterPoint_Y attributes.
- Line End Point: Divided into LineEndPoint_X and LineEndPoint_Y attributes.
- Line Azimuth: Adds azimuth angle for line objects.
- Hole Counts: Adds number of holes in region objects.
Length Unit: Specifies unit for geodesic perimeter calculations. 9 common units: Centimeter, Decimeter, Meter, Kilometer, Inch, Foot, Yard, Mile, Nautical Mile.
Area Unit: Specifies unit for geodesic area calculations. 14 common units: cm², dm², Square Meter, km², Hectare, Are, Acre, Square Inch, Square Foot, Square Yard, Square Mile, Square Nautical Mile, Mu, Chinese Acre.
Coordinate System: Coordinate system used for coordinate/length/area calculations. Defaults to dataset's current coordinate system.

Application Example

The following figure shows Beijing city boundary dataset attribute table. After calculating three geometric properties (center coordinates, geodesic area, and node count), results are shown in the right figure.