LiDAR vs Met Mast for Wind Resource Assessment: Which Is Bankable?

Every wind resource assessment starts with a measurement campaign, and the first decision is what to measure with: a meteorological mast, a ground-based LiDAR, or both. The choice sets the measurement and extrapolation uncertainty for the life of the project, so it feeds straight into the P90 and the debt a project can raise. Turbines have grown faster than masts, and that has changed the answer.

How each method measures the wind

Met mast

A met mast is a lattice or tubular tower fitted with cup or sonic anemometers at several heights, wind vanes, and temperature, pressure and humidity sensors. Each anemometer measures the wind at a single point and is calibrated in a wind tunnel to a traceable standard. Mast-mounted measurement is covered by IEC 61400-50-1, and a properly designed mast with calibrated cups is still the reference standard that everything else is checked against.

Vertical profiling LiDAR

A LiDAR (light detection and ranging) unit sits on the ground and fires a laser beam upwards in a cone. It measures the Doppler shift of light scattered back by dust and aerosols to work out wind speed and direction at a series of heights, typically from about 40 m to 200 m or more. Each reading is an average over a volume of air rather than a single point. Ground-based remote sensing for wind measurement is covered by IEC 61400-50-2.

Side-by-side comparison

• Measurement height: masts above 120 m are expensive and slow to permit, while LiDAR reaches the 140 m to 170 m hub heights of current turbines and measures across the whole rotor.
• Point accuracy: calibrated cups on a well-designed mast remain the benchmark. A verified LiDAR at a flat site performs close to that, but usually carries a slightly larger measurement uncertainty.
• Extrapolation: a short mast needs the wind speed extrapolated up to hub height using a shear model, which is often the largest single uncertainty in the campaign. LiDAR largely removes it.
• Terrain: masts measure correctly on any terrain. LiDAR needs a correction where the flow is not uniform across the scan cone.
• Data recovery: masts record continuously in nearly all weather. LiDAR availability drops in heavy rain, fog, very clean air, and when power supply fails at off-grid sites.
• Logistics: a mast needs foundations, guy wires, permits, and often aviation clearance. A LiDAR can be deployed in days and moved to a second location.
• Long-term record: a mast can stay in place for years and serve as the site reference during construction and operation. A LiDAR is normally deployed for a defined campaign.

Is LiDAR bankable?

For onshore projects on simple to moderate terrain, LiDAR data is now widely accepted by lenders and their technical advisors. Acceptance depends on evidence, not on the device. A lender's reviewer will look for:

• Pre-deployment verification of the specific unit against a calibrated reference mast, with the results and the verification report on file.
• A campaign that follows IEC 61400-50-2, including documented installation, configuration, and data filtering.
• High data recovery at hub height over at least twelve months, with gaps explained and filled transparently.
• Terrain corrections where needed, with the method and its uncertainty stated.
• A link to a long-term reference, either through a co-located mast or through a direct correlation with reanalysis data such as ERA5.

A LiDAR campaign that cannot show these is the one that gets a wider uncertainty, or a request for more measurement, during lender review.

Floating LiDAR offshore

Offshore, a fixed mast can cost many times more than onshore, so floating LiDAR buoys are now the usual first measurement for new zones. Bankability for a floating system is commonly judged against the Carbon Trust roadmap for commercial acceptance, which moves a system type from baseline to pre-commercial to commercial status based on validation trials against a reference. More on offshore campaigns on the offshore wind resource assessment page.

LiDAR in complex terrain

A vertical profiling LiDAR assumes the wind is the same everywhere across its scan cone. Over a ridge or a steep slope it is not: the flow curves and accelerates, and the beams on each side of the cone see different winds. The raw horizontal wind speed can then be wrong by a few percent, enough to move the P50 noticeably.

The standard fix is a flow-curvature correction from a CFD model of the site, ideally checked against a co-located mast for a period. With that correction in place, LiDAR is often the better tool in hilly terrain because it can be moved to several positions to capture how the resource changes across the site. See complex terrain wind resource assessment for how this feeds into the flow model.

Practical points for India and the Middle East

• Monsoon: heavy rain lowers LiDAR availability during the season that carries much of the annual energy at many Indian sites. A mast alongside the LiDAR protects the record, and the campaign must cover at least one full monsoon. See monsoon seasonality and long-term correction.
• Dust and heat: desert sites in Saudi Arabia usually give plenty of aerosol for the laser, but the lens window soils and cooling systems work hard. Cleaning visits and a reliable power supply decide the data recovery.
• Repowering: on existing wind farms, a LiDAR can measure shear up to the new hub height without a new tall mast, which is useful when modelling a repowered layout.
• Security and access: a LiDAR unit is valuable equipment on an open site, so fencing, monitoring, and remote alerts are part of the campaign budget.

The hybrid campaign most lenders prefer

For most projects the strongest campaign combines both methods. A mast, often 80 m to 120 m tall, provides a continuous, traceable record that can run for years and anchor the long-term correction. A LiDAR placed next to it measures the full wind profile up to and above hub height for at least part of that period, and can later be moved to a second position on the site.

The mast data fills gaps in the LiDAR record, the LiDAR removes most of the shear extrapolation, and the overlap shows the reviewer that both sets of data agree. In the uncertainty budget, that usually means a lower combined uncertainty than either method alone, and a higher P90.

How to choose

• Flat site, tight budget, early stage: a verified LiDAR for twelve months, correlated with a long-term reanalysis reference.
• Project heading to financing: a hybrid mast and LiDAR campaign, documented to IEC 61400-50-1 and 50-2.
• Complex terrain: a mast as the anchor plus a LiDAR moved between positions, with CFD-based terrain corrections.
• Existing short mast: add a LiDAR next to it rather than building a taller mast.
• Offshore: floating LiDAR at an appropriate maturity stage, validated before deployment.

Whichever method is used, the analysis matters as much as the hardware. Data filtering, gap filling, shear analysis, and long-term correction decide whether the measurement leads to a defensible energy yield. That work is set out on the met mast and LiDAR data analysis page.

Frequently asked questions