UM Geospatial Digital Special Collections

Citation: OpenStreetMap contributors (2023). Trinidad and Tobago Populated Places [gis dataset]. OpenStreetMap. https://www.openstreetmap.org/. last updated: 2024-10-28 (update frequency: As Needed). Abstract: A point feature set for populated places in Trinidad and Tobago. Key words: Trinidad and Tobago, populated places:towns, cities Open Geospatial Consortium Standards: dynamic vector tiles | | WMS (coming soon) | WFS (coming soon) Analytical Functions: gdsc_get_attributes(tablename=tt_populated_places,lat=25.718,lng=-80.279,identifier=name,attrs=[osm_id,name,place,other_tags],normal='') ETL documentation

ETL for tt_populated_places

######### # GDSC ETL is performed in two steps: shell script to ETL data into postgres # and then additional transformations with SQL in postGIS (if needed). #### ######### # Step 1 - bash script (pseudo code) #### # create directory structure and move into it mkdir -p /data/tt_populated_places/{download,etl} && cd /data/tt_populated_places # set update flag based on last update and update frequency do_update=0 if date() < last_update + update_frequency else do_update = 1 # download if update flag is set: if do_update == 1 then curl -o download/tt_populated_places.osm 'https://overpass-api.de/api/interpreter?data=node%5B%22place%22~%22city|town|village%22%5D(area:3600555717);(._;>;);out;' # load into postGIS with: ogr2ogr -lco GEOMETRY_NAME=geom -f PostgreSQL PG:"" download/tt_populated_places.osm ######### # Step 2 - SQL script (pseudo code): #### # Select proper geometry into the named table psql -d $POSTGRES_DB -U $POSTGRES_USER -p $POSTGRES_PORT -h postgis-bv241ywry6tzxsb2 -c " SELECT * INTO tt_populated_places FROM points; DROP TABLE IF EXISTS lines; DROP TABLE IF EXISTS multilinestrings; DROP TABLE IF EXISTS multipolygons; DROP TABLE IF EXISTS other_relations; DROP TABLE IF EXISTS points" # remove duplicate points and make geometries valid: UPDATE tt_populated_places SET geom=ST_MakeValid(ST_RemoveRepeatedPoints(geom));" # add local geometry column and reproject existing geometries into local EPSG: SELECT AddGeometryColumn ( 'tt_populated_places', 'geom_local',8035,'point',2 ); UPDATE tt_populated_places SET geom_local=ST_MakeValid(ST_RemoveRepeatedPoints(ST_Transform(geom,8035))); CREATE INDEX tt_populated_places_geom_local_idx ON tt_populated_places USING GIST (geom_local); NOTIFY pgrst, 'reload schema';"