feat(thing): expose observedArea on Thing for STAC and DCAT-AP spatial extent

api/app/models/thing.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from app.db.sqlalchemy_db import SCHEMA_NAME, Base
+from geoalchemy2 import Geometry
 from sqlalchemy.dialects.postgresql.json import JSON
 from sqlalchemy.orm import relationship
 from sqlalchemy.sql.schema import Column, ForeignKey
@@ -36,6 +37,7 @@ class Thing(Base):
     name = Column(String(255), nullable=False)
     description = Column(Text, nullable=False)
     properties = Column(JSON)
+    observed_area = Column("observedArea", Geometry)
     commit_id = Column(Integer, ForeignKey(f"{SCHEMA_NAME}.Commit.id"))
     location = relationship(
         "Location", secondary=Thing_Location, back_populates="thing"

api/app/sta2rest/sta2rest.py

@@ -128,6 +128,7 @@ class STA2REST:
             "name",
             "description",
             "properties",
+            "observed_area",
         ],
         "ThingTravelTime": [
             "id",
@@ -138,6 +139,7 @@ class STA2REST:
             "name",
             "description",
             "properties",
+            "observed_area",
             "system_time_validity",
         ],
         "HistoricalLocation": [

database/istsos_schema.sql

@@ -72,6 +72,17 @@ CREATE OR REPLACE FUNCTION "Datastreams@iot.navigationLink"(sensorthings."Thing"
     SELECT '/Things(' || $1.id || ')/Datastreams';
 $$ LANGUAGE SQL;
 
+CREATE OR REPLACE FUNCTION "observedArea"(sensorthings."Thing") RETURNS geometry AS $$
+BEGIN
+    RETURN (
+        SELECT ST_ConvexHull(ST_Collect(d."observedArea"))
+        FROM sensorthings."Datastream" d
+        WHERE d."thing_id" = $1.id
+          AND d."observedArea" IS NOT NULL
+    );
+END;
+$$ LANGUAGE plpgsql STABLE;
+
 CREATE TABLE IF NOT EXISTS sensorthings."Thing_Location" (
     "thing_id" BIGINT NOT NULL REFERENCES sensorthings."Thing"(id) ON DELETE CASCADE,
     "location_id" BIGINT NOT NULL REFERENCES sensorthings."Location"(id) ON DELETE CASCADE,