closestPoints (Stream Function)
Returns the closest coordinate to geo.json.geometry.fence.
Syntax
geo:closestPoints(<DOUBLE> longitude, <DOUBLE> latitude, <STRING> geo.json.geometry.fence)
Query Parameters
| Name | Description | Possible Data Types | Optional | Dynamic |
|---|---|---|---|---|
| longitude | Longitude of the geo location. | DOUBLE | No | No |
| latitude | Latitude of the geo location. | DOUBLE | No | No |
| geo.json.geometry.fence | String that contains geometry type and coordinates for a GeoJSON geometry fence. | String | No | No |
Extra Return Attributes
| Name | Description | Possible Data Types |
|---|---|---|
| closestPointOf1From2Latitude | closest point's latitude to the fence from the location. | DOUBLE |
| closestPointOf1From2Longitude | closest point's longitude to the fence from the location. | DOUBLE |
| closestPointOf2From1Latitude | closest point's latitude to the location from the fence. | DOUBLE |
| closestPointOf2From1Longitude | closest point's longitude to the location from the fence. | DOUBLE |
Example 1
geo:closestPoints(0.5, 0.5, "{'type':'Polygon','coordinates':[[[0, 0],[0, 2],[2, 2],[2, 0],[0, 0]]]}")
The geo:closestPoints() function identifies the closest points on the specified polygon from the given point (0.5, 0.5). The polygon is defined by the coordinates [[0, 0],[0, 2],[2, 2],[2, 0],[0, 0]]. The function returns 0.5, 0.5, 0.5, 0.5 as the nearest points on the polygon from the reference point.
Example 2
CREATE STREAM InputGeoStream (longitude double, latitude double, geoJsonFence string);
CREATE SINK STREAM OutputGeoStream (closestPointOf1From2Latitude double, closestPointOf1From2Longitude double, closestPointOf2From1Latitude double, closestPointOf2From1Longitude double);
@info(name = 'closestPoints')
INSERT INTO OutputGeoStream
SELECT closestPointOf1From2Latitude, closestPointOf1From2Longitude, closestPointOf2From1Latitude, closestPointOf2From1Longitude
FROM InputGeoStream#geo:closestPoints(longitude, latitude, geoJsonFence);
In this stream worker example, two streams are created: InputGeoStream for input data and OutputGeoStream for the output.
The InputGeoStream consists of longitude and latitude representing the geographical coordinates of a location, and geoJsonFence, which is a GeoJSON string that contains the geometry type and coordinates of a geographical fence.
The OutputGeoStream is set to receive the attributes closestPointOf1From2Latitude, closestPointOf1From2Longitude, closestPointOf2From1Latitude, and closestPointOf2From1Longitude, which respectively represent the closest point's latitude and longitude to the fence from the location and the closest point's latitude and longitude to the location from the fence.
The closestPoints query is defined to select and process events from the InputGeoStream using the function geo:closestPoints(longitude, latitude, geoJsonFence). This function calculates the closest points between the provided location and the defined GeoJSON fence.
The result of this function, which consists of the coordinates of the closest points between the location and the GeoJSON fence, is then inserted into the OutputGeoStream. This stream now holds the resulting closest point data for each processed event from the InputGeoStream.
In summary, this streaming data setup provides a mechanism to continually evaluate geographical data (longitude, latitude) against a GeoJSON-defined fence and output the closest points between the location and the fence.