About BGS
The British Geological Survey (BGS) is a world-leading geological survey and global geoscience organisation, focused on public-good science for government and research to understand earth and environmental processes.
BGS provides geological information for public and private sector users for use in areas such as construction project planning; finding sites for extracting geothermal energy or for storing carbon dioxide or nuclear waste; reducing the risk from natural hazards such as earthquakes or coastal erosion.
Dr. John A Stevenson is a Senior Software Developer for BGS with a background in volcanology. John’s speciality is Python-based software development, spatial data and data engineering. He spoke to us about BGS’ new QGIS-based field data capture tool and how they use it with Mergin Maps.
Developing a new survey tool
BGS has been doing digital field data capture since 2005 using a survey tool called the System for Integrated Geoscience Mapping (BGS-SIGMA), which was developed in-house and built on top of ESRI’s ArcGIS platform. The deprecation of ArcGIS by ESRI in favour of ArcPro in March 2024 meant that BGS-SIGMA would need to be replaced. After an internal review, we decided to move to an open-source system based on QGIS. This option was chosen because it gave the most flexibility in terms of customisation for their needs and for sharing with collaborators. QGIS was already widely used within BGS.
After evaluating both Mergin Maps and QField for integration of QGIS to mobile surveying, we decided to use Mergin Maps due to the simplicity of the platform and the ability for projects to run on desktop QGIS on a Windows-based tablet PC. This is similar to the workflow that we had with SIGMA but with the extra ability to synchronise between users via Mergin Maps.
BGS developers wrote a custom plugin to set up a project for geological mapping. The plugin adds layers to any QGIS project, with a GeoPackage to store the data and all the styles and forms configured as needed. It also makes it quicker to add data in a parent-child relationship in QGIS. There is a bulk photo importer tool that lets surveyors link photos to locations with the option to include captions and thumbnails, and which can detect unlinked photos. The plugin also has a tool to generate reports in HTML and PDF formats.
The plugin configures the project with standard QGIS layers backed by a GeoPackage, so data can be edited via plain QGIS (with or without the BGS plugin) or with the Mergin Maps mobile app. Using QGIS on the Windows tablets gives surveyors access to advanced GIS tools for generating slope or hillshade maps, measuring distances, or using planar surfaces to predict where rock formations are likely to outcrop at the surface. Using the mobile app gives the benefit of a more portable device with longer battery life for surveys in places such as areas, which are better suited for mobile devices. Someone walking around with a large rugged Windows tablet around their neck can draw unwanted attention, while someone tapping on a phone can just blend in.
Using database constraints to ensure data quality
The data collected in the field are ultimately destined for BGS’ central relational database, which has database-level constraints. These ensure high data quality by enforcing the data types and relationships between features. A survey is set up so that observations, photos, samples and structural measurements all belong to a single “locality” point, with the points belonging to one project. Database foreign key constraints make it impossible to record “orphan” data that doesn’t have a locality or project. Additional constraints are used, for example to ensure that “dip” angles of rock beds are between 0 and 90 degrees.
The BGS developers wanted to enforce the same constraints on the data at the point of collection. They did this at two levels - firstly in the QGIS forms, which understand foreign key relationships and can set constraints, and secondly, in the underlying GeoPackage. A GeoPackage is a SQLite database and can be configured with the same database constraints as in relational database management systems such as PostgreSQL or Oracle, guaranteeing that the data will be compatible. Use of SQLite-level constraints in a GeoPackage makes it impossible to record invalid data, but it is not a typical workflow. BGS and Lutra Consulting have been working together to update the Mergin Maps ecosystem so that database constraints will work smoothly.
Seamless integration from tablet to mobile to desktop
The key benefit of the integration between the BGS tool and Mergin Maps is the ease with which data can be moved between different contexts.
Our geologists appreciate having access to all relevant background mapping when in the field and being able to pinpoint their location via GPS. These maps can include Ordnance Survey mapping, aerial photos, digital elevation models, previous survey data, borehole data and even scans of handwritten “fieldslips” drawn by BGS geologists over our almost 200 year history.
Geologists can set up their QGIS project and collate background data on a laptop or desktop PC, then push it to the Mergin server to share with colleagues. In turn, they can pull it down onto rugged Windows tablets (via QGIS) or a mobile phone (via Mergin Maps), depending on their needs. All the layers and styling transfer across seamlessly and the data look the same in each format. On return to the office, data can be synchronised back via the server for work to continue on the laptop or desktop. A Python script uploads the final data to the central BGS data store.
Next steps
BGS have been using the new QGIS-based system for over a year now and data have been recorded from over 2,000 localities, with plans to flexibly expand the types of data that can be captured at each point. We are now working to release their plugin for wider use, beginning with foreign project partners and eventually submitting it to the QGIS Plugin Repository. Watch this space.
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Photo credits: All photos by John A Stevenson, licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)
