bcdata 0.9.0

Python tools for quick access to DataBC geo-data available via WFS

bcdata

Python and command line tools for quick access to DataBC geo-data available via WFS/WCS.

There is a wealth of British Columbia geographic information available as open data, but direct file download urls are not available and the syntax to accesss WFS via ogr2ogr and/or curl/wget can be awkward.

This Python module and CLI attempts to simplify downloads of BC geographic data and smoothly integrate with PostGIS and Python GIS tools like geopandas, fiona and rasterio. As noted above, the module is an interface only to geographic data avialable via WFS/WCS - to work with other BC open data, use the bcdata R package.

Disclaimer
It is the user's responsibility to check the licensing for any downloads, data are generally licensed as OGL-BC

Dependencies and installation

bcdata requires gdal. If working with an OS such as linux or MacOS, with gdal already installed to a known location, install with pip:

$ pip install bcdata

Alternatively, conda can be used to install/manage the required dependencies as per the GeoPandas guide:

$ conda create --name bcdataenv
$ conda activate bcdataenv
$ conda config --env --add channels conda-forge
$ conda config --env --set channel_priority strict
$ conda install python=3 geopandas
$ conda install rasterio
$ pip install bcdata

Configuration

Default PostgreSQL database

The default target database connection (used by bc2pg) can be set via the DATABASE_URL environment variable (the password parameter should not be required if using a .pgpass file)

Linux/Mac: export DATABASE_URL=postgresql://{username}:{password}@{hostname}:{port}/{database}

Windows: SET DATABASE_URL=postgresql://{username}:{password}@{hostname}:{port}/{database}

Layer list / layer schema cache

To reduce the volume of requests, information about data requested is cached locally. Schemas of individual layers that have previously been requested are cached with the cache file name matching the object/table name. Location of the cache defaults to ~/.bcdata but can be moditified by setting the BCDATA_CACHE environment variable:

export BCDATA_CACHE=/path/to/bcdata_cache

The cache will automatically refresh after 30 days - force a cache refresh by deleting the files in the cache or the entire cache folder.

Usage

Typical usage will involve a manual search of the DataBC Catalogue to find a layer of interest. Once a dataset of interest is found, note the key with which to retreive it. This can be either the id/package name (the last portion of the url) or the Object Name (Under Object Description).

For example, for BC Airports, either of these keys will work:

• id/package name: bc-airports
• object name: WHSE_IMAGERY_AND_BASE_MAPS.GSR_AIRPORTS_SVW

Note that some packages may have more than one layer - if you request a package like this, bcdata will prompt you with a list of valid object/table names to use instead of the package name.

Python module

import bcdata

# get a feature as geojson
geojson = bcdata.get_data(
    'bc-airports',
    query="AIRPORT_NAME='Terrace (Northwest Regional) Airport'"
)
geojson
{'type': 'FeatureCollection', 'features': [{'type': 'Feature', 'id': 'WHSE_IMAGERY_AND_BASE_MAPS.GSR_AIRPORTS_SVW.fid-f0cdbe4_16811fe142b_-6f34', 'geometry': {'type': 'Point', ...

# optionally, load data as a geopandas GeoDataFrame
gdf = bcdata.get_data(
    'bc-airports',
    query="AIRPORT_NAME='Terrace (Northwest Regional) Airport'",
    as_gdf=True
)
gdf.head()
AERODROME_STATUS AIRCRAFT_ACCESS_IND                          AIRPORT_NAME                ...                TC_LID_CODE WEBSITE_URL                          geometry
0        Certified                   Y  Terrace (Northwest Regional) Airport                ...                       None        None  POINT (-128.5783333 54.46861111)

CLI

Commands available via the bcdata command line interface are documented with the --help option:

$ bcdata --help

Usage: bcdata [OPTIONS] COMMAND [ARGS]...

Options:
  --version  Show the version and exit.
  --help     Show this message and exit.

Commands:
  bc2pg  Download a DataBC WFS layer to postgres
  cat    Write DataBC features to stdout as GeoJSON feature objects.
  dem    Dump BC DEM to TIFF
  dump   Write DataBC features to stdout as GeoJSON feature collection.
  info   Print basic metadata about a DataBC WFS layer as JSON.
  list   List DataBC layers available via WFS

bc2pg

$ bcdata bc2pg --help

Usage: bcdata bc2pg [OPTIONS] DATASET

  Download a DataBC WFS layer to postgres

   $ bcdata bc2pg bc-airports --db_url postgresql://postgres:postgres@localhost:5432/postgis

Options:
  -db, --db_url TEXT      Target database url, defaults to $DATABASE_URL
                          environment variable if set
  --table TEXT            Destination table name
  --schema TEXT           Destination schema name
  --geometry_type TEXT    Spatial type of geometry column
  --query TEXT            A valid CQL or ECQL query
  -c, --count INTEGER     Total number of features to load
  -k, --primary_key TEXT  Primary key of dataset
  -s, --sortby TEXT       Name of sort field
  -e, --schema_only       Create empty table from catalogue schema
  -a, --append            Append to existing table
  -t, --no_timestamp      Do not log download to bcdata.log
  -v, --verbose           Increase verbosity.
  -q, --quiet             Decrease verbosity.
  --help                  Show this message and exit.

cat

$ bcdata cat --help

Usage: bcdata cat [OPTIONS] DATASET

  Write DataBC features to stdout as GeoJSON feature objects.

Options:
  --query TEXT                    A valid CQL or ECQL query
  --bounds TEXT                   Bounds: "left bottom right top" or "[left,
                                  bottom, right, top]". Coordinates are BC
                                  Albers (default) or --bounds_crs
  --indent INTEGER                Indentation level for JSON output
  --compact / --not-compact       Use compact separators (',', ':').
  --dst-crs, --dst_crs TEXT       Destination CRS
  -s, --sortby TEXT               Name of sort field
  --bounds-crs, --bounds_crs TEXT
                                  CRS of provided bounds
  -l, --lowercase                 Write column/properties names as lowercase
  -v, --verbose                   Increase verbosity.
  -q, --quiet                     Decrease verbosity.
  --help                          Show this message and exit.

dem

$ bcdata dem --help

Usage: bcdata dem [OPTIONS]

  Dump BC DEM to TIFF

Options:
  -o, --out_file TEXT             Output file
  --bounds TEXT                   Bounds: "left bottom right top" or "[left,
                                  bottom, right, top]". Coordinates are BC
                                  Albers (default) or --bounds_crs  [required]
  --dst-crs, --dst_crs TEXT       Destination CRS
  --bounds-crs, --bounds_crs TEXT
                                  CRS of provided bounds
  -r, --resolution INTEGER
  -a, --align                     Align provided bounds to provincial standard
  -i, --interpolation [nearest|bilinear|bicubic]
  -v, --verbose                   Increase verbosity.
  -q, --quiet                     Decrease verbosity.
  --help                          Show this message and exit.

dump

$ bcdata dump --help

Usage: bcdata dump [OPTIONS] DATASET

  Write DataBC features to stdout as GeoJSON feature collection.

    $ bcdata dump bc-airports
    $ bcdata dump bc-airports --query "AIRPORT_NAME='Victoria Harbour (Shoal Point) Heliport'"
    $ bcdata dump bc-airports --bounds xmin ymin xmax ymax

   It can also be combined to read bounds of a feature dataset using Fiona:
   $ bcdata dump bc-airports --bounds $(fio info aoi.shp --bounds)

Options:
  --query TEXT                    A valid CQL or ECQL query
  -o, --out_file TEXT             Output file
  --bounds TEXT                   Bounds: "left bottom right top" or "[left,
                                  bottom, right, top]". Coordinates are BC
                                  Albers (default) or --bounds_crs
  --bounds-crs, --bounds_crs TEXT
                                  CRS of provided bounds
  -l, --lowercase                 Write column/properties names as lowercase
  -v, --verbose                   Increase verbosity.
  -q, --quiet                     Decrease verbosity.
  --help                          Show this message and exit.

info

$ bcdata info --help

Usage: bcdata info [OPTIONS] DATASET

  Print basic metadata about a DataBC WFS layer as JSON.

  Optionally print a single metadata item as a string.

Options:
  --indent INTEGER  Indentation level for JSON output
  --count           Print the count of features.
  --name            Print the table name of the dateset.
  --description     Print the description of the dateset.
  -v, --verbose     Increase verbosity.
  -q, --quiet       Decrease verbosity.
  --help            Show this message and exit.

list

$ bcdata list --help

Usage: bcdata list [OPTIONS]

  List DataBC layers available via WFS

Options:
  --help         Show this message and exit.

CLI notes

Note that bc2pg creates bcdata.log and logs the most recent download date for each table downloaded. Disable with the switch --no_timestamp if you do not wish to create this table.

Example of a record in bcdata.log:

mydb=# select * from bcdata.log;
                 table_name                  |        latest_download
---------------------------------------------+-------------------------------
 whse_imagery_and_base_maps.gsr_airports_svw | 2021-02-17 11:50:34.044481-08

CLI examples

Search the data listing for airports:

  $ bcdata list | grep AIRPORTS
  WHSE_IMAGERY_AND_BASE_MAPS.GSR_AIRPORTS_SVW

Describe a dataset. Note that if we know the id of a dataset, we can use that rather than the object name:

$ bcdata info bc-airports --indent 2
{
  "name": "WHSE_IMAGERY_AND_BASE_MAPS.GSR_AIRPORTS_SVW",
  "count": 455,
  "schema": {
    "properties": {
      "CUSTODIAN_ORG_DESCRIPTION": "string",
      "BUSINESS_CATEGORY_CLASS": "string",
      "BUSINESS_CATEGORY_DESCRIPTION": "string",
      "OCCUPANT_TYPE_DESCRIPTION": "string",
      ...etc...
    },
    "geometry": "GeometryCollection",
    "geometry_column": "SHAPE"
  }
}

The JSON output can be manipulated with jq. For example, to show only the fields available in the dataset:

$ bcdata info bc-airports | jq '.schema.properties'
{
  "CUSTODIAN_ORG_DESCRIPTION": "string",
  "BUSINESS_CATEGORY_CLASS": "string",
  "BUSINESS_CATEGORY_DESCRIPTION": "string",
  "OCCUPANT_TYPE_DESCRIPTION": "string",
  etc...
}

Dump data to geojson (EPSG:4326 only):

$ bcdata dump bc-airports > bc-airports.geojson

Get a single feature and send it to geojsonio (requires geojson-cli). Note the double quotes required around a CQL FILTER provided to the --query option.

$ bcdata dump \
  WHSE_IMAGERY_AND_BASE_MAPS.GSR_AIRPORTS_SVW \
  --query "AIRPORT_NAME='Terrace (Northwest Regional) Airport'" \
   | geojsonio

Save a layer to a geopackage in BC Albers:

$ bcdata cat bc-airports --dst-crs EPSG:3005 \
  | fio collect \
  | fio load -f GPKG --dst-crs EPSG:3005 airports.gpkg

Note that this will not work if the source data has mixed geometry types.

Load data to postgres and run a spatial query:

$ bcdata bc2pg bc-airports \
    --db_url postgresql://postgres:postgres@localhost:5432/postgis

$ bcdata bc2pg WHSE_LEGAL_ADMIN_BOUNDARIES.ABMS_MUNICIPALITIES_SP \
    --db_url postgresql://postgres:postgres@localhost:5432/postgis

$ psql -c \
  "SELECT airport_name
   FROM whse_imagery_and_base_maps.gsr_airports_svw a
   INNER JOIN whse_legal_admin_boundaries.abms_municipalities_sp m
   ON ST_Intersects(a.geom, m.geom)
   WHERE admin_area_name LIKE '%Victoria%'"
                           airport_name
------------------------------------------------------------------
 Victoria Harbour (Camel Point) Heliport
 Victoria Inner Harbour Airport (Victoria Harbour Water Airport)
 Victoria Harbour (Shoal Point) Heliport
(3 rows)

Projections / CRS

CLI

bcdata dump returns GeoJSON in WGS84 (EPSG:4326).

bcdata cat provides the --dst-crs option, use any CRS the WFS server supports.

bcdata bc2pg loads data to PostgreSQL in BC Albers (EPSG:3005).

Python module

bcdata.get_data() defaults to EPSG:4236 but any CRS can be specified (that the server will accept).

Development and testing

bc2pg tests require database postgresql://postgres@localhost:5432/test_bcdata exists and has PostGIS installed:

psql -c "create database test_bcdata"
psql test_bcdata -c "create extension postgis"

Create virtualenv and install bcdata in development mode:

$ mkdir bcdata_env
$ virtualenv bcdata_env
$ source bcdata_env/bin/activate
(bcdata_env)$ git clone [e-mail]:smnorris/bcdata.git
(bcdata_env)$ cd bcdata
(bcdata_env)$ pip install -e .[test]
(bcdata_env)$ py.test

Other implementations

• bcdata R package - official BC Open Data R client
• OWSLib - used internally by bcdata
• pgsql-ogr-fdw - read WFS data directly into with postgres foreign data wrapper
• general purpose command line tools (ogr2ogr/curl/wget)