In 2009, a team flew a Central American forest with LiDAR. Once the trees were removed from the model, the screen showed square kilometres of geometric structures: streets, terraces, reservoirs. An entire city, under the canopy, that generations of explorers had walked through without seeing it. Archaeology relives this scene with each new survey.
In a decade, LiDAR has become one of the most powerful prospecting tools in the discipline. Not because it digs — it touches nothing — but because it lets you look at the ground as if the vegetation did not exist.
Bare earth, stripped of the trees
Everything rests on the digital terrain model. By keeping only the points classified as “ground” (see the geomatics pipeline), you obtain a terrain surface without forest. The micro-relief shaped by humans — embankments, ditches, levelled foundations, old sunken roads, burial mounds — often persists in the topography long after vegetation has covered it. The DTM preserves it; you just have to know how to bring it out.
Hillshade: giving relief to the eye
A raw elevation model, in greyscale, says nothing. The reigning technique is to light it artificially — the analytical hillshade. You simulate a low, grazing sun: the slightest bumps cast a shadow, the hollows darken. A structure twenty centimetres high, imperceptible on foot, becomes a sharp figure on screen.
You add no information: you make visible what the data already contained. Changing the angle of the light brings out details another lighting concealed.
Archaeologists in fact combine several lightings, or derived methods (topographic openness, local relief, slope maps), so as not to miss structures aligned with the direction of the light — which cast no shadow of their own.
What this changes for research
Before, prospecting a dense forest meant walking transects, blind. LiDAR reverses the logic: you first spot promising anomalies on screen, then go and check the most convincing ones on site. The yield of field campaigns is multiplied, and structures that no dig would have crossed by chance enter the field of research.
In Québec, this same 1 m bare earth helps document the heritage of the territory: old routes, vanished agricultural layouts, traces of occupation in wooded areas. The data was not acquired for archaeology, but it serves it admirably.
You are already using hillshade
The 2D view of Québec 3D is a hillshade of the LiDAR relief — the same technique as the archaeologists. Look for old roads, banks, shapes too regular to be natural.
Scrutinize the relief →A necessary caution
A topographic anomaly is not proof. A regular bank may be a remnant… or a logging windrow, a recent field boundary, a processing artefact. LiDAR guides the eye; only field verification, carried out by specialists and within the legal framework for heritage, decides. The tool identifies candidates, it does not sign off discoveries.
The takeaway
By digitally removing the forest and raking the ground with oblique light, LiDAR made visible an entire layer of the past that escaped the eye. This may be its most spectacular use: not to measure the present, but to reveal what the landscape had patiently buried.