C-DRONE GUIDE · 21 JULY 2026
Vegetation mapping under power lines by drone LiDAR: the legal clearance obligation and price
A tree growing too close to a power conductor does not wait for the next storm to become a problem: a single branch creeping within a few tens of centimetres is enough to cause a flashover, a power cut or a fire outbreak. French law therefore requires grid operators and neighbouring landowners to maintain a safety clearance all year round, under what is known as the legal clearance obligation (obligation légale de débroussaillement, OLD). A drone fitted with LiDAR has become the reference tool for measuring that clearance over dozens of kilometres of line, rather than section by section with binoculars. Here is how this mapping works, who is responsible for what, and what it costs in 2026.
Published on 21 July 2026, reviewed on 28 July 2026 — regulations in force as of July 2026.
Why vegetation under a power line cannot be left to grow unchecked
Contact between a branch and a live conductor triggers an electrical flashover: an arc that can cut power to an entire neighbourhood and, in dry conditions, instantly ignite the surrounding vegetation. Enedis and RTE run tree-clearing campaigns every year along their networks to prevent this risk, an obligation that is stepped up in the high wildfire-risk areas of southern France, where forest cover grows back quickly between two campaigns. Storms make the problem worse still: a weakened tree or a broken branch can tip into the line's easement without having crossed the regulatory clearance distance the day before.
The difficulty is not knowing that clearing is required, but knowing exactly where and by when. A medium-voltage distribution network crosses dozens of towns, private forests, farmland and private gardens: a foot patrol, binoculars in hand, can neither measure a clearance in centimetres nor anticipate how much a tree will grow over the next two or three years. That is the gap drone LiDAR mapping has filled, by objectively measuring the real distance between every conductor and the nearest vegetation, section by section.
How a drone LiDAR survey measures the real clearance between trees and conductors
The drone follows the line's route on an automated flight, at a constant height above the corridor, while its LiDAR sensor fires several hundred thousand laser pulses per second. Each returning echo forms a point in a 3D cloud: unlike a photo, the laser partly penetrates foliage and captures both the ground and the structure of the trees, making it possible to reconstruct the terrain beneath the canopy — a limitation of standard photogrammetry we cover in our guide to drone photogrammetry software. Automated processing then classifies every point: ground, conductor (whose sag follows a catenary curve, modelled precisely against the current tension and temperature), pylon, or vegetation.
Once that classification is done, the software calculates, for every tree, the shortest distance to the nearest conductor and compares it against the regulatory safety clearance. The most useful part goes beyond an instant snapshot: a study by Cano-Solís, Ballesteros and Branch-Bedoya, published in 2023 in the journal Data, built a reference dataset for training automatic vegetation-segmentation models from drone orthomosaics along power line corridors, a direction several research teams are now extending with growth models: by estimating the age and species of each tree detected, they project its height two or three years ahead and flag in advance the trees that will cross the clearance limit before the next pruning campaign. The drone, however, performs no cutting itself: no current framework allows a drone to prune vegetation near a live line on its own, so the service remains entirely a measurement and mapping mission, handed over afterwards to the teams who intervene on the ground or from a cherry picker.
The regulatory framework: who must clear vegetation, and by when
The legal clearance obligation (obligation légale de débroussaillement, OLD) around power transmission and distribution lines is codified in articles L.134-10 to L.134-12 of the forestry code (code forestier). The width of the cleared strips on either side of the line is set by the competent administrative authority, never exceeding 100 m in total; in practice it varies with the line's voltage, the height of the surrounding vegetation and the département's wildfire-risk level. The infrastructure operator must notify affected landowners at least 10 working days before work begins: once a month has passed without work starting, that notice lapses and must be renewed. Landowners cannot object to the clearing itself, but retain the right to be informed of its schedule.
Responsibility is split according to land ownership: when the tree and the line stand on the same plot, Enedis or RTE handles the pruning. When the tree grows on a neighbouring plot, it is up to that plot's owner to carry out the maintenance at their own expense, or to hire an approved contractor, after notifying the grid operator — a distinction that LiDAR mapping can settle plot by plot precisely because the data is registered against cadastral boundaries. On the civil aviation side, an isolated rural overflight most often falls under open category A2 or A3; a corridor several kilometres long, particularly when flown beyond visual line of sight, shifts to the specific category STS-02, as we detail in our guide to open versus specific category. Checking regulated zones on the Géoportail map before any mission remains systematic.
What the report handed to the operator or landowner contains
The typical deliverable combines a 3D model of the corridor, a colour-coded linear map (red for a clearance already below the regulatory threshold, orange for a tree projected to cross that threshold within the next two to three years based on the growth projection, green for a compliant situation) and a table listing every tree to watch with its GPS coordinates, cadastral reference and the measured clearance in centimetres. That granularity lets the grid operator prioritise its pruning teams on the genuinely critical sections rather than treating the whole corridor uniformly, and lets a neighbouring landowner know exactly which trees on their land are concerned before Enedis gets in touch.
This service complements drone power line inspection, which focuses on the condition of pylons and insulators rather than the surrounding vegetation, and draws on the same LiDAR expertise detailed in our guide to forestry drone inventory. On corridors crossing forests classified as wildfire-prone, the data also feeds into drone wildfire prevention patrols, with vegetation under power lines counting among the checkpoints local authorities review every summer.
Price of a drone power-line vegetation survey in 2026
The price mainly depends on the length of the corridor, the density of vegetation to classify and the level of detail expected (a simple compliance check or a multi-year growth projection). Orders of magnitude observed in France in 2026:
| Service | Observed price (excl. VAT) |
|---|---|
| Feasibility study and corridor segmentation | €400 to €900 |
| LiDAR survey and vegetation/conductor classification, per km | €350 to €650/km, tapered beyond 10 km |
| Compliance report with colour-coded map and plot-by-plot list | €500 to €1,200 per campaign |
| 2–3 year growth-projection option | +20 to 35% of the LiDAR survey |
| Recurring annual monitoring (multi-year subscription) | -15 to 25% per following campaign |
As with power line inspection, this market remains largely structured by framework contracts between grid operators and specialist providers, but forestry cooperatives, forest-owning municipalities and large landowners along a corridor also commission one-off missions to assess their own situation before Enedis contacts them. Recurring monitoring spreads the regulatory setup cost across several campaigns rather than repeating it in full every year.
Frequently asked questions about drone vegetation mapping under power lines
Can the drone cut or prune the branches it detects? No: no current framework allows a drone to physically intervene near a live line. The mission is limited to measurement and mapping; pruning is still carried out by teams on the ground or from a cherry picker.
Who pays to prune a tree on my land that stands close to a line? If the tree and the line are on the same plot, the grid operator covers the work. If the tree grows on your plot next to the easement, maintenance remains your responsibility, after notifying the operator.
Does the mapping replace a visit from an Enedis or RTE agent? No: it objectifies the situation and prioritises interventions, but the final decision and the work itself remain the responsibility of the grid operator or the approved contractor it appoints.
How often should this kind of survey be repeated? An annual or two-yearly rhythm is common in fast-growing or high wildfire-risk areas; a longer cycle is enough for slow-growing species outside sensitive zones.