Overview
Discrete Global Grid Systems
A Discrete Global Grid Systems (DGGS) is a unique type of spatial reference system comprising of a hierarchy of uniquely identifiable discrete grid cells that span the globe at multiple resolutions. Several schemes for tesselation and indexing schemes exist and DGGS can support efficient management, storage, integration, exploration, mining, and visualisation of large geospatial datasets. We conduct research into innovative DGGS indexing and storage software and query APIs to integrate, visualise and analyse arbitrary raster and vector data and perform ML workloads on DGGS-based datacubes.
Watch the DGGS Teaser on our YouTube channel.
We are scoping joint activities to further the development and applicatons of DGGS, e.g. with the Pangeo community. As a result the goal of the xdggs library was conceived – to facilitate working with multiple Discrete Global Grid Systems (DGGSs) via a unified, high-level and user-friendly API that is deeply integrated with Xarray. This document describes the in-memory representation of DGGS data in Python environments.
We had a talk and an article accepted for the FOSS4G Europe 2024 conference, July 01–07 in Tartu, Estonia. There were classic free and open-source geospatial topics, but also an increasing touch of EO.
Each of these 4 grid systems are generated with two subsequent resolutions to depict the “aperture” and parent child spatial relationships. ISEA4H (hexagons), ISEA4T (triangles) generated with DGGRID – a free software program for creating and manipulating Discrete Global Grids. Uber H3 and Landcare Research/Manaaki Whenua RhealPixDGGS-py. Source: A. Kmoch, Landscape Geoinformatics (2022)
Kmoch, A., Vasilyev, I., Virro, H., & Uuemaa, E. (2022). Area and shape distortions in open-source discrete global grid systems. Big Earth Data, 6(3), 256–275. DOI
We hosted a DGGS workshop as part of the AGILE Conference 2021 (Association of Geographic Information Laboratories in Europe) in June 2021:
The main objective of this workshop was introducing the attendees to the theoretical background of Discrete Global Grid Systems (DGGS), current real-world implementations with exemplary use cases. In subsequent discussion, we discussed additional use cases and the convergence of DGGS with traditional GIS and Spatial Analysis methods for non-expert impactful adoption of DGGS.
pydggsapi - an open-source web API
pydggsapi (GitHub repository) is an open-source web API to discover DGGS datasets through the OGC DGGS API standard.
The increasing popularity over the past few years in using the Discrete Global Grid System (DGGS) for geoscience applications demonstrates the demand for an easy and standardised way of publishing and accessing DGGS data. The need is perfectly addressed by the OGC DGGS API standard, which emphasises answering the questions of “What is here?” and “Where is it?”.
With the purpose above, the Landscape and Geoinformatics lab, in collaboration with Francis Charette Migneault from the Computer Research Institute of Montréal (CRIM), has developed an open-source web API, pydggsapi, which adheres to the OGC DGGS API standard, enabling users to discover DGGS datasets. Users can explore data in various types of DGGRS (Discrete Global Grid Reference System), such as IGEO7, H3, IVEA7H, and rHEALPix, with a simple web query. The API endpoints allow users to make queries on the area of interest by:
- Retrieve a list of zones at a specific refinement level for the area of interest using a bounding box (where is it?)
- Retrieve data for a particular zone using the zone data retrieval query (what is here?)
The above two queries demonstrated the most basic queries that users can perform with the API. There are several advanced features, such as the CQL2 filter and the datetime query parameter, that allow users to work with custom data queries and on temporal datasets. Users can find more details about the queries in the example notebook (documentation).
In addition to the DGGS API endpoints, users can explore the collections provided by the API instances integrated with the OGC Collection API. Another feature of our API implementation is the tiles-api. This API endpoint allows users to easily visualise DGGS datasets with any GIS software by simply adding vector tiles.
The API is still in the early stages of development. We keep improving the functionality and usability through various use cases from different disciplines.
