Arc_length

geometric-functions arc_length

syntax

  • arc_length(arc_poly_dataitem, valuesunit of coordinate system)

definition

arc_length(arc_poly_dataitem, valuesunit) calculates the length of an arc or the outline of a polygon data-item arc_poly_dataitem.

The resulting values-unit is configured as second argument. This gives an interpretation to the resulting values. It does not convert them. For example, if the coordinate system is in meters, then the resulting output are meter, but you should also configure it to be interpreted as meters. If you want kilometers as output, you’ll have to manually convert it to km.

description

The definition of the outline of a polygon is only equal to the perimeter if the polygon has no islands and lakes.

In case a polygon consits of multiple rings, the outline also contains the artificial lines needed to relate the rings, see polygon data model.

If you want to calculate the perimeter, use a split_polygon function first to make different polygons for all exterior rings (the outline of the lakes are still a part of the calculated arc_length).

applies to

example

attribute<meter> road_length (Road) := arc_length(road/geometry, meter);
road/geometry road_length
{2 {399246, 112631}{398599, 111866}} 1001.92
{3 {398599, 111866}{399495, 111924} {401801,111524}} 3238.31
{2 {401529, 114921}{398584, 114823} 2946.63

domain Road, nr of rows = 3