Bridge & Bedrock

If you’ve been in this industry more than about five minutes, you’ll know that half of geotechnical engineering is actually detective work. Before you can say anything sensible about ground conditions, you need to know where you are, what’s around you, and what’s happened on that patch of ground over the last few hundred years. That’s where QGIS comes in.

QGIS is a free, open-source Geographic Information System. In plain terms, it’s a piece of software that lets you layer maps, data and imagery on top of each other so you can actually see the story of a site rather than just read about it in a desk study report. It handles vector data (points, lines, polygons like site boundaries or borehole locations), raster data (images like aerial photos or elevation models), and everything in between.

Every geotechnical engineer, engineering geologist or graduate should have this installed on their laptop. Not because it’s trendy, but because it quietly becomes the tool you reach for on almost every job, from a two-borehole extension survey to a multi-phase quarry restoration scheme. And because it’s free, there’s genuinely no excuse. You’re not waiting on a software licence to become available, you’re not sharing a single seat between six engineers, and you’re not having an awkward conversation with your line manager about budget just to open a shapefile.

It’s worth being clear about what QGIS isn’t, though. It’s not a replacement for AutoCAD, Civil 3D or your logging software. It doesn’t replace CAD for detailed design drawings, and it’s not built for producing construction-ready output. What it does brilliantly is sit alongside those tools as the place where you bring spatial data together, interrogate it, and then export exactly what you need into your CAD environment. Think of it as the research and reconnaissance layer that happens before, and often during, the CAD work.

Why GIS Matters in Geotechnical Engineering

Almost every project you’ll ever work on starts with the same question: where is it, and what’s around it? Before you’ve drilled a single borehole, you need to understand the spatial context of a site: its geology, its history, its hazards, its constraints.

Spatial data underpins everything we do. Mapping constraints such as mining legacy, flood zones, contaminated land or protected habitats can make or break a scheme, and they’re almost always easier to understand visually than as a list in a table. Geological interpretation benefits enormously from being able to see solid and drift geology mapped against topography and site boundaries, rather than squinting at a paper BGS sheet. Planning applications increasingly demand spatial evidence, and environmental assessments rely on overlaying watercourses, abstraction points and ecological designations. Even quarry management, from reserve estimation to progressive restoration planning, is fundamentally a spatial problem.

GIS matters because geotechnical engineering is inherently three-dimensional and site-specific, and no amount of tabulated data replaces the insight you get from seeing everything overlaid in one place.

Installing QGIS

Getting started is refreshingly painless. Head to qgis.org, download the installer for your operating system, and run it. There’s no licence key, no dongle, no phone call to a reseller.

You’ll be asked to choose between the Long-Term Release (LTR) and the latest release. For day-to-day professional use, I’d recommend the LTR. It’s more stable, better tested, and less likely to throw up plugin compatibility issues halfway through a deadline. The latest release has newer features, which is great if you like living on the edge, but for client-facing work I’d rather have stability than novelty.

Once installed, it’s worth spending ten minutes setting up a few recommended plugins (more on my favourites later) and getting your head around Coordinate Reference Systems, or CRS. This is genuinely the single most important concept to understand before you do anything else in QGIS. Get your CRS wrong and everything from distance measurements to overlay alignment will be subtly, frustratingly wrong. In the UK, you’ll mostly be working in OSGB36 / British National Grid (EPSG:27700), but you’ll also encounter WGS84 (EPSG:4326) from GPS devices and web sources. QGIS handles reprojection on the fly, but only if you understand what’s happening.

Essential Features Every Geotechnical Engineer Should Know

Importing CAD drawings. QGIS can read DWG and DXF files directly, which means you can bring in a topographic survey or a site layout drawing and georeference it against real-world coordinates. This is invaluable when a CAD file has been drawn in a local or arbitrary grid and you need to check it actually sits where it should.

Loading Ordnance Survey mapping. Whether through OS OpenData layers or a paid API connection, having OS base mapping underneath everything gives you instant context: roads, buildings, watercourses, field boundaries. It’s the backdrop against which everything else makes sense.

Geological maps. Digitised geology, whether from BGS or historic sources, lets you see solid and superficial geology in relation to your site boundary rather than trying to mentally translate a paper map.

British Geological Survey datasets. The BGS provides an enormous amount of free data: borehole records, geological indicators, landslide susceptibility, mining records and more. Bringing these into QGIS as WMS layers or downloaded shapefiles turns a desk study from a literature review into a genuine spatial analysis.

LiDAR terrain models. Environment Agency LiDAR data, often available at 1m or better resolution, gives you a detailed digital terrain model. This is superb for understanding slope angles, drainage patterns and subtle topographic features that might indicate old workings or landslip.

Environment Agency datasets. Flood zones, historic flood outlines, and river network data all help build a picture of flood risk without needing to commission a separate flood consultant just to get a first impression.

Historic mapping. Old OS county series and epoch maps are gold dust for identifying historic quarries, mine workings, filled ground, ponds and industrial land use that might not appear on any modern map.

Aerial photography. Overlaying current and historic aerial imagery helps identify recent site changes, vegetation, made ground, and features that a walkover alone might miss, especially useful for sites you haven’t visited yet.

Planning constraints. Local authority and national planning layers, conservation areas, green belt, mineral safeguarding areas, help you understand the regulatory context early.

Site boundaries. Simple, but fundamental. Digitising or importing a site boundary as the first layer anchors everything else you do.

Shapefiles. Still the most common vector data format you’ll receive from clients, consultants and government bodies. QGIS handles them natively and effortlessly.

KML/KMZ files. Common when clients send you a Google Earth file with “the site is roughly here” marked on it. QGIS opens these without fuss and lets you convert them into something more useful.

GPS survey data. Field-collected points, whether from a handheld GPS or a survey-grade GNSS unit, can be imported directly and checked against other spatial layers.

Drone survey outputs. Orthomosaics and point clouds from drone surveys can be draped over terrain models, giving you an extremely current and detailed view of site conditions.

Practical Geotechnical Applications

A Phase 1 desk study is transformed by QGIS. Instead of a written narrative referencing separate maps, you build a single spatial picture: historic mapping, BGS geology, EA flood data, mining records and site boundary all in one place, which makes identifying constraints faster and far less likely to miss something.

For quarry reserve assessments, overlaying geological boundaries, topography and extraction limits lets you estimate volumes and visualise remaining reserves against planning boundaries directly.

Slope stability studies benefit from LiDAR-derived slope angle and aspect rasters, letting you quickly identify areas of concern before committing resources to detailed ground investigation.

Planning restoration schemes for quarries or landfill sites is inherently spatial, and QGIS lets you model phased restoration contours and land use against the existing terrain.

Selecting borehole locations becomes far more defensible when you can justify positions against geology, access constraints, historic features and previous investigation points, all visible together.

Flood risk assessments and surface water interpretation are naturally suited to GIS, since watercourses, catchments and flood extents are all spatial datasets that overlay directly onto your site.

Catchment analysis, using terrain models to delineate drainage catchments, helps with everything from SuDS design input to understanding groundwater recharge patterns.

Site walkover planning improves hugely when you can pre-mark features of interest from aerial imagery and historic mapping before you even put your boots on, saving time in the field and making sure you don’t miss anything.

Infrastructure route selection benefits from being able to compare multiple corridor options against geology, constraints and topography simultaneously.

Mining risk assessments rely heavily on BGS and Coal Authority spatial data, and having these layered against your site boundary is far more informative than a written report alone.

Landfill engineering, from leachate management to capping design, benefits from terrain and hydrological analysis that GIS handles naturally.

My Typical Workflow

On a fairly typical site investigation project, my workflow looks something like this. I receive a site boundary from the client, often as a KML or a rough sketch, and digitise or import it properly. I load OS mapping as a base layer, then bring in BGS geology to understand solid and drift conditions. Next, I overlay LiDAR data to get a feel for topography and drainage. I add historical OS mapping to check for old workings, ponds or made ground. I check mining constraints through Coal Authority or BGS data where relevant. I review current and historic aerial imagery for anything that jumps out. Finally, I export tidy maps for the report and, where needed, export georeferenced data into CAD or LSS for borehole logging and cross-section work.

This workflow saves time because it front-loads the risk identification before ground investigation starts, meaning fewer surprises, better-targeted boreholes, and a desk study that’s genuinely informed by data rather than assumption.

Hidden Features Worth Knowing

A few features that don’t get talked about enough: hillshade generation from a DEM gives you an instant, intuitive view of subtle terrain features. Terrain profiles let you draw a line across a site and generate an elevation profile in seconds, brilliant for quick slope checks. The Raster Calculator is superb for deriving slope angle or difference models between two terrain datasets. Contour creation from LiDAR is far quicker than you’d expect. Coordinate transformations let you reproject data between grids reliably. Georeferencing PDFs means you can take a scanned historic plan and pin it accurately to real-world coordinates. Attribute tables and expressions let you query and filter data intelligently, for example isolating only boreholes above a certain depth. Print layouts give you proper, presentable map outputs for reports. And batch processing can save hours when you need to clip or reproject dozens of files at once.

Common Beginner Mistakes

Using the wrong coordinate system is the classic. Always check your project CRS matches your data, and reproject deliberately rather than by accident. Not checking projection compounds this, particularly when combining UK data with anything sourced internationally. Forgetting layer order catches people out constantly, a polygon layer sitting above your raster will simply hide it. Confusing raster and vector data, and trying to apply the wrong tool to the wrong data type, wastes time. Working in degrees instead of metres, usually because you’re still in WGS84, makes distance and area measurements meaningless, so always reproject to a metric grid like British National Grid before measuring anything. And not clipping datasets to your area of interest leads to sluggish performance and cluttered maps when a national dataset would have been fine cut down to your site extent.

My Favourite Plugins

QuickMapServices is brilliant for quickly adding base maps without hunting for WMS links. Georeferencer, built into QGIS core, is essential for pinning historic plans and scanned drawings into place. QGIS2threejs is a fun and genuinely useful way to visualise terrain and geology in 3D for client presentations. The Profile Tool (or the built-in terrain profile in newer versions) is invaluable for quick slope sections. And DXF/DWG import tools, again largely built into core QGIS now, smooth the CAD interoperability considerably.

Strengths and Limitations

QGIS excels at spatial analysis, data visualisation, desk study work and bringing together disparate datasets quickly and cheaply. It’s fantastic for early-stage constraint mapping, historic research and communicating spatial findings clearly.

Where it falls short is detailed engineering design. You wouldn’t produce a retaining wall detail in QGIS, and you wouldn’t build a slope stability cross-section model in it either. Specialist software like Civil 3D, AutoCAD, LSS or Slide2 remains essential for that detailed, calculation-driven work.

The good news is integration is generally straightforward. QGIS can export to DXF for AutoCAD or Civil 3D, and exported coordinate data or georeferenced backgrounds work well when brought into LSS for logging and cross-sections. It’s genuinely complementary rather than competing software.

Five Tips for New Users

Start by getting comfortable with CRS before anything else, it will save you endless headaches later. Use QuickMapServices early on so you always have context underneath your data. Get into the habit of clipping national datasets to your project area rather than loading everything nationwide. Save your project regularly and use relative paths so your project file stays portable between machines. And don’t be afraid to right-click everything, the context menus in QGIS are where most of the useful functionality hides.

Key Takeaways

• QGIS is free, powerful, and genuinely useful for real geotechnical work, not just a novelty for GIS specialists.
• It complements CAD and specialist geotechnical software rather than replacing it.
• Understanding coordinate reference systems properly is the single most important skill to develop early.
• BGS, OS, LiDAR, Environment Agency and historic mapping datasets combined in QGIS transform the quality of desk studies.
• A consistent personal workflow, from boundary to export, saves time and reduces the chance of missing site constraints.
• A handful of plugins and hidden features (hillshade, terrain profiles, georeferencing) punch well above their weight.

Coming Next…

In Software Spotlight #3, we’ll move from mapping to modelling, with a look at Slide2 and practical slope stability analysis, including how it fits into real-world geotechnical workflows and where it earns its keep on site.