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C-DRONE GUIDE · 26 JULY 2026

Vineyard and crop water stress by drone: thermal, multispectral, irrigation, price

Hotter summers, water restrictions, irrigation quotas: agricultural water is now managed to the drop. Yet water stress is not visible uniformly from the edge of the plot — it settles in patches, following soil, exposure and rooting, well before foliage wilts. That is exactly what the drone measures: a water-deprived plant closes its stomata, transpires less and heats up, and that rise in canopy temperature can be mapped with a thermal camera. Combined with multispectral imagery measuring vigour, it turns an impression into an actionable map: where to irrigate first, where water is not lacking, where a sector is failing. Here are the method, its honest limits and 2026 prices.

Published on 26 July 2026, reviewed on 1 August 2026 — regulations in force as of August 2026.

Canopy temperature, an early indicator of water shortage

The physics is simple: transpiration cools the leaf. When water runs short, the plant closes its stomata to protect itself, transpiration drops and foliage temperature rises one to several degrees above that of a well-supplied plant. The onboard thermal camera measures this canopy temperature across the whole plot in one flight, and it is converted into a normalised index — the CWSI (crop water stress index) — which factors out the day's conditions by comparing against wet and dry references.

The scientific validation of the drone approach is long-standing and solid: a study by Baluja and co-authors published in 2012 in Irrigation Science showed, on a vineyard, that thermal and multispectral indices measured by drone correlate well with the vines' actual water status measured on the ground (stem water potential, stomatal conductance), opening the way to mapping within-plot water variability (see the study on Google Scholar). In other words: a drone's thermal map reflects what a technician would measure vine by vine, but across the whole plot in an hour.

Thermal + multispectral: reading the two maps together

The thermal map alone is not enough: a warm zone can be a less vigorous row (less foliage, more bare soil in the pixel) as much as a thirsty one. That is why both sensors fly together: the multispectral camera (NDVI, NDRE indices) maps vigour and leaf area, the thermal camera maps temperature. Crossed, the two maps tell situations apart: normal vigour + high temperature = probable water stress; low vigour + high temperature = an older problem (soil, disease, rooting) needing a different diagnosis.

In viticulture this cross-reading also serves quality: moderate, controlled water stress is sought on some red varieties, and the map lets you harvest zones with different profiles separately. In irrigated field crops and orchards, it feeds the irrigation plan directly: sectors to bring forward, sectors to space out, clogged drippers or failed sprinklers showing up as cold or warm geometric patterns. The same sensors also serve agricultural damage assessment and agrivoltaic plot monitoring, where shading precisely alters the water balance.

When to fly, how often, with what limits

Thermal flights happen in the middle of the day, under clear skies and moderate wind: it is at peak evaporative demand that differences between stressed and unstressed plants are most readable — the opposite of building thermography, which avoids the sun. The useful season runs from fruit set to veraison for vines, and covers the sensitive stages (flowering, grain filling) for summer crops. Two to four well-timed flights beat weekly monitoring: the goal is to inform irrigation decisions when they are actually made.

The limits to know: the measurement concerns the visible canopy (grassed inter-rows or young low-cover plantings need specific processing to exclude soil), calibration requires stable conditions during the flight, and the map shows where and how much in relative terms — for absolute control, it is anchored to a few ground measurements (capacitance probes, pressure chamber) which remain the agronomic reference. The drone does not replace the agronomist: it gives them the map that makes their point measurements extrapolable to the whole plot.

Regulations: flying over farmland

Over farmland outside built-up areas, the mission almost always falls under the European open category: C1 or C2 class drone, 120 m height limit, visual line of sight, outside the restricted zones of the official drone map (aerodrome surroundings, low-altitude military areas). The professional pilot is registered as a UAS operator and the drone declared on AlphaTango. No prefectural authorisation is needed in rural areas — the flight still requires the consent of the farmer whose plots are overflown.

One precision point to anticipate: for two campaigns' maps to compare pixel to pixel, georeferencing must be careful. An RTK drone or a few ground targets suffice — our guide RTK/PPK: when to require centimetre accuracy details when that investment is justified. For plots near a town or under an aerodrome control zone, the provider checks constraints beforehand, as for any mission described on our agricultural drone page.

Observed prices in 2026

Ranges observed in 2026 for a thermal + multispectral campaign (excl. VAT):

Multispectral alone (vigour, no thermal) is noticeably cheaper; calibrated thermal with ground anchoring sits at the top of these ranges. Set against the price of water, pumping energy and the yield losses of a sector failing unseen, the flight pays for itself in the first dry season. Request a quote stating crop, area and irrigation system.

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Put it into practice

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