Class SpatialDistance

Namespace

YndigoBlue.Velocity.Functions

Assembly

YndigoBlue.Velocity.dll

Represents the ST_Distance spatial function that calculates the minimum distance between two geometries or geographies.

public class SpatialDistance : Function, ICheckItem, IDefaultItem, IFilterItem, IElement

Inheritance

object

Function

SpatialDistance

Implements

ICheckItem

IDefaultItem

IFilterItem

IElement

Remarks

Warning

Spatial functions are not available in the Community Edition of Velocity. They require the Full Edition.

The ST_Distance function returns the shortest distance between two spatial objects. For Geometry types (planar), it calculates Euclidean distance in the coordinate system units. For Geography types (spherical), it calculates great-circle distance on the earth's surface, optionally in specified units. This is useful for proximity queries, finding nearest neighbors, or spatial indexing. OGC-compliant.

Return Type: Numeric (float/double). Units depend on coordinate system or specified UnitOfMeasure.

Distance Calculation Rules:

Relationship	Distance Result
Geometries touch or overlap	0
Geometries are separate	Minimum distance between closest points
One inside the other	0 (they overlap)

Example Results: ST_Distance(PY0, X)

Shape X	Distance (in degrees)
PY1 (inside PY0)	0 - contained within
PY2 (outside PY0)	2° - gap between edges
PY3 (touches PY0)	0 - shares boundary
PT1 (inside PY0)	0 - point within polygon
PT2 (outside PY0)	3° - horizontal distance to edge
LN1 (inside PY0)	0 - line within polygon

Units of Measure: For Geography types, use UnitOfMeasure to get results in meters, kilometers, miles, or other supported units.

UnitOfMeasure	Result (GA at -102°,38° to GB at -96°,43°, approx. 750 km)
Meter	750,000
Kilometer	750
Mile	466
Foot	2,460,630
Yard	820,210
Inch	29,527,559

Examples

Calculate the distance from each store to a target point, ordering by proximity:

var schema = manager.LoadSchema("retail");
var stores = schema["stores"];
var target = new Point(new Coordinate(-73.9857, 40.7484));

var query = new Query()
    .Select([ stores["id"], stores["name"], new Expression("dist", new SpatialDistance(stores["location"], target)) ])
    .From(stores)
    .OrderBy(new Expression("dist", new SpatialDistance(stores["location"], target)));

var results = manager.Retrieve(query);

Constructors

SpatialDistance(Geometry, Column)

Initializes a new instance of ST_Distance with a Geometry literal and a column.

SpatialDistance(Geometry, Function)

Initializes a new instance of ST_Distance with a Geometry literal and function result for function chaining.

SpatialDistance(Column, Geometry)

Initializes a new instance of ST_Distance with a column and a Geometry literal.

SpatialDistance(Column, Column)

Initializes a new instance of ST_Distance with two columns for spatial joins.

SpatialDistance(Column, Column, UnitOfMeasure)

Initializes a new instance of ST_Distance with two columns and unit of measure for spatial joins.

SpatialDistance(Column, Function)

Initializes a new instance of ST_Distance with a column and function result for function chaining.

SpatialDistance(Column, Function, UnitOfMeasure)

Initializes a new instance of ST_Distance with a column, function result, and unit of measure for function chaining.

SpatialDistance(Column, Geography)

Initializes a new instance of ST_Distance with a column and a Geography literal.

SpatialDistance(Column, Geography, UnitOfMeasure)

Initializes a new instance of ST_Distance with a column, Geography, and unit of measure.

SpatialDistance(Function, Geometry)

Initializes a new instance of ST_Distance with a function result and Geometry literal for function chaining.

SpatialDistance(Function, Column)

Initializes a new instance of ST_Distance with a function result and column for function chaining.

SpatialDistance(Function, Column, UnitOfMeasure)

Initializes a new instance of ST_Distance with a function result, column, and unit of measure for function chaining.

SpatialDistance(Function, Function)

Initializes a new instance of ST_Distance with two function results for function chaining.

SpatialDistance(Function, Function, UnitOfMeasure)

Initializes a new instance of ST_Distance with two function results and unit of measure for function chaining.

SpatialDistance(Function, Geography)

Initializes a new instance of ST_Distance with a function result and Geography literal for function chaining.

SpatialDistance(Function, Geography, UnitOfMeasure)

Initializes a new instance of ST_Distance with a function result, Geography literal, and unit of measure for function chaining.

SpatialDistance(Geography, Column)

Initializes a new instance of ST_Distance with a Geography literal and a column.

SpatialDistance(Geography, Column, UnitOfMeasure)

Initializes a new instance of ST_Distance with a Geography, column, and unit of measure.

SpatialDistance(Geography, Function)

Initializes a new instance of ST_Distance with a Geography literal and function result for function chaining.

SpatialDistance(Geography, Function, UnitOfMeasure)

Initializes a new instance of ST_Distance with a Geography literal, function result, and unit of measure for function chaining.