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