Building geological cross-sections with GeoProfiler: simpler and more flexible

[Thanks to chatGPT for helping]

The GeoProfiler module in qgSurf is an attempt to make geological profile creation workflow less painful and more reproducible. GeoProfiler is built around a three-step workflow:

1.    (optional) Create (or reuse) a 3D topographic profile layer 
2.    Tell GeoProfiler which 3D profile layer you want to work on
3.    Add geological data and generate a configurable plot

Steps 1 and 3 are the “real work”. Step 2 is the glue: a small but crucial step where you just define the working 3D line layer.

What makes GeoProfiler really useful, especially from a field-geologist’s point of view, is that it allows you to think in terms of geological problems, not in terms of software tools.

Very often, when we build a cross-section, the hardest part is not drawing the line — it is deciding how the terrain should be cut in order to see something meaningful. Sometimes we want a single clean section, sometimes we want to see how the same structures evolve a few hundred meters to the left and to the right.

With GeoProfiler, this becomes natural. You can create a single topographic section, when you just need one good line across your structure — or a small set of parallel sections, when you want to compare how things change laterally. This is especially helpful for understanding the geometry of thrust systems, fold trains, or fault zones that widen or branch with distance. Instead of repeating the work five times, you simply define one baseline and let the tool generate parallel profiles around it.

Another big step forward is that profiles are no longer forced to be straight lines.
In earlier tools, the section had to be rigid: point A to point B, perfectly linear. But that is rarely how we actually think in the field. Sometimes the most meaningful section follows a valley floor, bends around a ridge, or gently curves to intersect key geological features. GeoProfiler allows those curved (but still geologically reasonable) sections, so the resulting profiles feel closer to the way we would sketch them in a notebook.

A third aspect that matters a lot in real projects is that our datasets almost never “fit” each other perfectly.
A DEM from one source, vector geology from another source, structural stations collected with yet another coordinate system. GeoProfiler is designed to work across different map projections, handling the transformations internally so that everything is brought consistently onto the profile. Instead of fighting with reprojections and fear of small misalignments, you can focus on what each dataset is telling you.

Once the profile (or profiles) exist, the geological part becomes straightforward: you can start adding what you would normally reason about in a cross-section — fault traces intersecting the terrain, lithological units cutting across the line, scattered point data such as measurements or events, or structural attitudes that define planes dipping into or out of the section. Bit by bit, the profile becomes not just a topographic cut, but a genuine geological interpretation space.

The detailed technical options are all documented in the help — the intention here is simpler: GeoProfiler tries to reduce the friction between thinking like a geologist and working inside a GIS. It gives you sections that behave more like the ones we sketch in the field, while still being reproducible, measurable, and connected to real data.

 

Modifications:

2026-01-06: added hyperlink to qgSurf plugin repository