Point

From ObjectVision

Jump to: navigation, search

concept


The next topics on this page describe the point data item. The point function is described on the point() page.

In the GeoDMS point data items are used for:

Vector data

The feature attribute of point vector data always refers to one coordinate for each element in the domain.

Vector data if often read from a shape file, but x and y attributes can also easily be read as numeric attributes from other data sources and combined with a point function to a feature attribute, as in the next example.

unit<uint32> residence
:   StorageName = "=System/DbName"
,   SqlString         = "SELECT * FROM Residences ORDER BY id"
{
   attribute<coord_rd> x;
   attribute<coord_rd> y;
   attribute<point_rd>  geometry := point(x, y, point_rd);
}

The x and y attributes are read from the data source with as values unit coord_rd. The geometry data item combines both x and y coordinate with the point function to create a two dimensional data item of coordinates. The values unit of this geometry attribute is point_rd, defining the coordinate system.

Subitems of the location item can be configured to define multiple visualisation styles.

Grid data

As the nature of Grid data is two-dimensional, the identification of a grid cell in a Grid Domain is also two-dimensional.

Personal tools