Geometry Type Designators

Listed below are the geometry type designators used to describe the exact nature of a Feature's spatial component(s).

Designator Value Type Description
GEOMETRY object GeoJSON Geometry object
POINT GEOMETRY GeoJSON Point geometry
MULTI-POINT GEOMETRY GeoJSON MultiPoint geometry
LINE-STRING GEOMETRY GeoJSON LineString geometry
MULTI-LINE-STRING GEOMETRY GeoJSON MultiLineString geometry
POLYGON GEOMETRY GeoJSON Polygon geometry
MULTI-POLYGON GEOMETRY GeoJSON MultiPolygon geometry
POLYGONAL POLYGON or MULTI-POLYGON Option of POLYGON or MULTI-POLYGON geometry
LINEAL LINE-STRING or MULTI-LINE-STRING Option of LINE-STRING or MULTI-LINE-STRING geometry
DISPLAY-POINT POINT POINT based representation of Polygonal or Lineal Features

Display-point

A Display Point represents a curated, Point-based representation of a non-puntal Feature.

  • Display Points are members of a Feature's "property" object
  • Display Points MUST be captured as GeoJSON Point objects
  • Display Points MUST be within the geometry of the Feature that possesses it
  • Display Points SHOULD be positioned in a location where map label "collision" is least expected

Horizontal Positional Accuracy

Features that explicitly reference this rule-set MUST be within +/- 5 meters of their actual ground location when tested using an independent source of higher accuracy.

  • The independent source of higher accuracy shall be of the highest accuracy feasible and practicable to evaluate the accuracy of the feature

Polygon Winding Order

RFC 7946, Section 3.1.6 states the following when describing Polygons and the winding order of linear rings:

"A linear ring MUST follow the right-hand rule with respect to the area it bounds, i.e., exterior rings are counterclockwise, and holes are clockwise." Note: The [GJ2008] specification did not discuss linear ring winding order. For backwards compatibility, parsers SHOULD NOT reject Polygons that do not follow the right-hand rule.

As a result, Features with polygonal geometries that do not follow the right-hand rule will NOT be rejected at this time, but MAY produce informative warnings if and when observed.

Precision

Precision SHOULD be at least seven (7) decimal places.

  • Seven (7) decimal places is equivalent to a planar distance of ~11mm which is tolerable for mapping and surveying purposes