One of the most common frustrations in early-stage architectural and engineering work is tracking down reliable contour data. You check Google Earth. You dig through your metro’s GIS portal. You try Google Maps. And you come up empty — or close enough to it that the data isn’t useful.
Here’s a tool that solves that problem.
One Map: Contours for Any South African Site
One Map (onemap.co.za) is a subscription-based mapping service with a free tier that gives you access to contour overlays for sites across South Africa. For initial feasibility and concept work, it’s one of the most practical tools available locally.
The contours are displayed at 5 metre intervals — enough resolution for early site analysis, section studies, and understanding the general topography of a site before you’ve commissioned a survey.
How to Turn Contours On
The interface is a little clunky, so here’s the exact sequence:
- Open your site in One Map.
- Click Workspace and Layers in the side panel.
- Select Overlays.
- Find NGI and enable Relief Lines.
You can toggle this layer on and off as needed. Once it’s active, you’ll see contour lines across your site with elevation values labelled directly on the map.
What It’s Good For
- Early site analysis — understanding slope, drainage direction, and level changes before a survey is commissioned.
- Concept design — informing split-level decisions, retaining wall locations, and building placement.
- Client presentations — a quick visual read of the topography that non-technical clients can follow.
- Rural and peri-urban sites — particularly useful where municipal GIS data is sparse or outdated.
A Word of Caution
One Map contours are useful for initial thinking and planning. They are not a substitute for a registered land surveyor’s certified contours, which you’ll need before submitting for local authority approval or moving into detailed design. Treat this data as a starting point, not a deliverable.
Other Sources Worth Knowing
If One Map doesn’t suit your workflow, a few alternatives are worth having in your toolkit:
- Chief Directorate: National Geo-spatial Information (NGI) — the underlying data source One Map draws from. You can sometimes download raw DXF or shapefile contours directly for use in CAD or Revit.
- SANSA Earth Observation — useful for large rural sites where NGI coverage becomes patchy.
- Google Earth Pro (free desktop app) — the elevation profile tool along a path can be handy for quick cross-sections, and you can export KMZ overlays.
Whenever we find a tool that saves time on the unglamorous parts of the job, we’ll share it here. If you have your own go-to resources for site data in South Africa, drop them in the comments — we’d like to know what others are using.
noh ARCHITECTS 