UM Geospatial Digital Special Collections

Citation: University of Richmond's Digital Scholarship Lab (2020). Miami-Dade Home Owner's Loan Corporation (HOLC) Neighborhood Redlining Grade [gis dataset]. University of Richmond's Digital Scholarship Lab. https://services.arcgis.com/jIL9msH9OI208GCb/arcgis/rest/services/HOLC_Neighborhood_Redlining/FeatureServer. last updated: 2024-10-28 (update frequency: Never). Abstract: The historical redlining grade from 143 cities across the United States. This dataset is the subset for Miami-Dade County in Florida. Key words: Florida, Miami-Dade County, MDC, Housing, Property, Racial Inequality, Race, Redlining History, HOLC, Social Justice Open Geospatial Consortium Standards: dynamic vector tiles | | WMS (coming soon) | WFS (coming soon) ESRI Standards: ArcGIS MapServer | ArcGIS FeatureServer | Open in ArcGIS Portal for GDSC Analytical Functions: gdsc_get_attributes(tablename=mdc_holc_redlining,lat=25.718,lng=-80.279,identifier=holc_grade,attrs=[holc_grade,city,holc,code,st,citystate],normal='') gdsc_nearest_neighbor(table=mdc_holc_redlining,lat=25.718,lng=-80.279,id=holc_grade) ETL documentation

ETL for mdc_holc_redlining

######### # 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/mdc_holc_redlining/{download,etl} && cd /data/mdc_holc_redlining # 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 ogr2ogr -nln mdc_holc_redlining download/mdc_holc_redlining.geojson "https://services.arcgis.com/jIL9msH9OI208GCb/ArcGIS/rest/services/HOLC_Neighborhood_Redlining/FeatureServer/0/query?where=city=%27Miami%27&outFields=*&outSR=4326&f=json" # replace column names Shape__Length and Shape__Area to avoid conflict when # providing as service on ArcServer. sed -i 's/Shape__Length/shape_length/gI; s/Shape__Area/shape_area/gI' download/mdc_holc_redlining.geojson # load into postGIS with: ogr2ogr -lco GEOMETRY_NAME=geom -f PostgreSQL PG:"" download/mdc_holc_redlining.geojson -nlt multipolygon -nln mdc_holc_redlining ######### # Step 2 - SQL script (pseudo code): #### # remove duplicate points and make geometries valid: UPDATE mdc_holc_redlining SET geom=ST_MakeValid(ST_RemoveRepeatedPoints(geom));" # add local geometry column and reproject existing geometries into local EPSG: SELECT AddGeometryColumn ( 'mdc_holc_redlining', 'geom_local',2236,'multipolygon',2 ); UPDATE mdc_holc_redlining SET geom_local=ST_MakeValid(ST_RemoveRepeatedPoints(ST_Transform(ST_Multi(geom),2236))); CREATE INDEX mdc_holc_redlining_geom_local_idx ON mdc_holc_redlining USING GIST (geom_local); NOTIFY pgrst, 'reload schema';"cd /data/mdc_holc_redlining/ mkdir -p derived # Create pg_dump and downloadable zip of table in derivate directory pg_dump -d $POSTGRES_DB -U $POSTGRES_USER -p $POSTGRES_PORT -h postgis-e43b1q10x1kr5qh0 -t mdc_holc_redlining > derived/mdc_holc_redlining.sql tar -czf derived/mdc_holc_redlining.sql.tar.gz meta_dcat_mdc_holc_redlining.json -C derived mdc_holc_redlining.sql