Exercise 6 - Metadata via OGC API - Records

OGC API - Records provides a Web API with the capability to create, modify, and query metadata on the Web:

OGC API - Records: Part 1: Core (draft)

OGC API - Records uses OGC API - Features as a building block, thus enabling streamlined deployment and integration for clients and users.

pygeoapi support

pygeoapi supports the OGC API - Records draft specification, using Elasticsearch and TinyDB rasterio as core backends.

Note

See the official documentation for more information on supported catalogue/metadata backends

Publish metadata records in pygeoapi

With pygeoapi we can setup OGC API - Records using any supported data provider. In this exercise we will use the TinyDB Catalogue backend. We will use the sample catalogue in workshop/exercises/data/records/catalogue.tinydb.

Update the pygeoapi configuration

Open the pygeoapi configuration file in a text editor. Add a new dataset section as follows:

    example_catalogue:
        type: collection
        title: FOSS4G Florence Record catalogue
        description: FOSS4G Florence Record catalogue (OGC API - Records)
        keywords:
            - Services
            - Infrastructures
            - Florence
            - FOSS4G
        links:
            - type: text/html
              rel: canonical
              title: information
              href: http://opendata.comune.firenze.it
              hreflang: en-US
        extents:
            spatial:
                bbox: [11.145, 43.718, 11.348, 43.84]
                crs: http://www.opengis.net/def/crs/OGC/1.3/CRS84
        providers:
            - type: record
              name: TinyDBCatalogue
              data: /data/records/catalogue.tinydb
              id_field: externalId
              time_field: recordCreated
              title_field: title

Save the configuration and restart Docker Compose. Navigate to http://localhost:5000/collections to evaluate whether the new dataset has been published.

Metadata formats

By default, pygeoapi supports and expects the OGC API - Records core record model and queryables. For additional metadata formats, you can develop your own custom pygeoapi plugin, or convert your metadata to OGC API - Records core record model before adding to pygeoapi.

Install OWSLib

If you do not have Python installed, consider running this exercise in a Docker container. See the Setup Chapter.

pip3 install owslib

Sample ISO 19139 to TinyDBCatalogue loader

It is possible to load more example ISO19139 metadata in a TinyDB database with the following script (raw):

cd workshop/exercises/data/records
curl -O https://raw.githubusercontent.com/geopython/pygeoapi/master/tests/load_tinydb_records.py
python3 load_tinydb_records.py xml catalogue.tinydb

If you do not have curl installed, copy the URL above to your web browser and save locally.

If you do not have Python installed, you can the loader by using the OWSLib Docker container. See the Setup Chapter.

Using the OWSLib Docker container to load metadata

Linux/MacWindows

cd workshop/exercises
docker run -it --rm --network=host --name owslib -v $(pwd)/data:/data python:3.10-slim /bin/bash
pip3 install owslib
apt-get update -y && apt-get install curl -y
curl -O https://raw.githubusercontent.com/geopython/pygeoapi/master/tests/load_tinydb_records.py
python3 load_tinydb_records.py /data/records/xml /data/records/catalogue.tinydb

cd workshop/exercises
docker run -it --rm --network=host --name owslib -v $(pwd)/data:/data python:3.10-slim /bin/bash
pip3 install owslib
apt-get update -y && apt-get install curl -y
curl -O https://raw.githubusercontent.com/geopython/pygeoapi/master/tests/load_tinydb_records.py
python3 load_tinydb_records.py /data/records/xml /data/records/catalogue.tinydb

Navigate to http://localhost:5000/collections/example_catalogue to evaluate whether the new metadata has been published to the collection.

Tip

pygeometa is a Python package to generate metadata for geospatial datasets. pygeometa allows for managing metadata in simple YAML "metadata control files (MCF), and supports import, export as well as transformations for many geospatial metadata formats. OGC API - Records metadata can be produced using pygeometa, either from MCF files or transforming from other formats.

Install and run pygeometa per below to get an idea of the various commands and functionality (as well, consult the tutorial).

pip3 install pygeometa
pygeometa --help

pygeoapi as a CSW proxy

You can check the "pygeoapi as a Bridge to Other Services" section to learn how to publish CSW as OGC API - Records.

Client access

QGIS

QGIS supports OGC API - Records via the MetaSearch plugin. MetaSearch originally focused on Catalogue Service for the Web (OGC:CSW) only, but has been extended to OGC API - Records. MetaSearch is a default plugin in QGIS and requires no further installation.

Query OGC API - Records from QGIS

Follow these steps to connect to a service and query datasets:

Locate the MetaSearch plugin in the Web menu or on the Toolbar . The main search panel will appear with the default MetaSearch catalogue list already populated.

Pre-populated catalogues

open the Services tab, to find the New button to create a new connection
add a connection to https://demo.pygeoapi.io/master
click Service Info to get information about the service
return to the Search tab
select the connection you have just created
type a search term and click search
notice that when you select a search result, a red footprint is drawn on the map highlighting the location of the dataset

OWSLib is a Python library to interact with OGC Web Services and supports a number of OGC APIs including OGC API - Records.

Interact with OGC API - Records via OWSLib

If you do not have Python installed, consider running this exercise in a Docker container. See the Setup Chapter.

pip3 install owslib

Then start a Python console session with: python3 (stop the session by typing exit()).

>>> from owslib.ogcapi.records import Records
>>> SERVICE_URL = 'https://demo.pygeoapi.io/master/'
>>> w = Records(SERVICE_URL)
>>> w.url
'https://demo.pygeoapi.io/master'
>>> dutch_metacat = w.collection('dutch-metadata')
>>> dutch_metacat['id']
'dutch-metadata'
>>> dutch_metacat['title']
'Sample metadata records from Dutch Nationaal georegister'
>>> dutch_metacat['description']
'Sample metadata records from Dutch Nationaal georegister'
>>> dutch_metacat_query = w.collection_items('dutch-metadata', limit=1)
>>> dutch_metacat_query['numberMatched']
198
>>> dutch_metacat_query['numberReturned']
1
>>> dutch_metacat_query = w.collection_items('dutch-metadata', q='Wegpanorama')
>>> dutch_metacat_query['numberMatched']
2

Note

See the official OWSLib documentation for more examples.

Summary

Congratulations! You are now able to publish metadata to pygeoapi.