Technology / Engineering guide
Wind Direction, Nacelle Heading & Yaw Angle Conventions
A yaw-angle comparison requires compatible definitions. Wind direction may describe where air comes from; an equipment axis describes where a component points. A convention mismatch can resemble a large alignment error.
Agree what each angle means before subtracting.
Define zero, rotation direction and the physical axis for each signal. Then resolve circular wrapping and timestamps. These definitions explain records without prescribing a MARSTON control algorithm.
01 / Wind from
A wind direction is not a flow-to arrow.
NOAA NDBC defines its wind direction as the direction the wind comes from, measured clockwise from true north.
NOAA NDBC defines its wind direction as the direction the wind comes from, measured clockwise from true north. Under that convention, an easterly wind is reported as 90° while the air travels towards 270°. The two angles describe the same airflow with opposite directional meanings.
Confirm the convention of the actual site dataset rather than assuming every instrument or export follows it. A diagram must label whether its arrow points towards the wind source or along the moving air. Otherwise a correct meteorological value can be compared with the wrong physical axis.
02 / Nacelle axis
Heading needs a defined physical direction.
A heading record should identify which nacelle or rotor-related axis it describes and which end is positive.
A heading record should identify which nacelle or rotor-related axis it describes and which end is positive. “Nacelle direction” alone does not establish whether the signal points towards the incoming wind, along the airflow or along a mechanical reference chosen for the equipment.
Use the applicable assembly drawing and signal definition to establish that meaning. Do not infer it from a photograph or assume a common zero offset across models. A bearing position, a heading and a yaw-command value can be different quantities even when all are expressed in degrees.
03 / Common reference
Resolve the frame before calculating an angle.
Record whether zero represents true north, magnetic north or an equipment-specific reference, and whether increasing values run clockwise or counterclockwise.
Record whether zero represents true north, magnetic north or an equipment-specific reference, and whether increasing values run clockwise or counterclockwise. Also identify absolute versus relative angles. A relative yaw position cannot be directly compared with an absolute wind bearing without a documented relationship between their frames.
Write any approved conversion into the calculation record, retaining the original values and conventions. This is a data-definition task, not a direction to recalibrate a device or change a controller setting. An unexplained offset in a spreadsheet should not become an accepted alignment correction.
04 / Angle wrapping
Handle the circular boundary explicitly.
As a purely illustrative comparison, suppose two compatible directional axes are measured clockwise from the same zero.
As a purely illustrative comparison, suppose two compatible directional axes are measured clockwise from the same zero. If their readings are 350° and 10°, their shortest unsigned separation is 20°, although ordinary subtraction gives a magnitude of 340°. Both values lie close to the same circular boundary.
A signed difference additionally requires a stated sign and range convention. For example, defining the wrapped first-minus-second difference within −180° to +180° gives −20° in that example. This explains arithmetic only; it does not specify a motor command, permitted cable rotation, deadband or automatic yaw strategy.
05 / Time and quality
Compare signals representing the same condition.
Keep timestamps, averaging periods, validity indicators and equipment state with each angle.
Keep timestamps, averaging periods, validity indicators and equipment state with each angle. A delayed heading observation and a newer wind direction may show an apparent mismatch that is partly a timing issue. Do not remove those differences by silently mixing instantaneous and averaged records.
Angles also require circular treatment when averaging: 350° and 10° should not be interpreted as a simple arithmetic mean pointing south. State the averaging method used by the data source. At poorly defined wind conditions, retain quality notes rather than forcing every reported angle into an alignment conclusion.
06 / Signal dictionary
Keep interpretation separate from control capability.
Create a signal dictionary covering physical meaning, reference, sign, units, time basis and source.
Create a signal dictionary covering physical meaning, reference, sign, units, time basis and source. Identify measured, calculated and commanded values, and whether the equipment provides each channel. Do not assume an unconfirmed sensor list or communication capability.
MARSTON’s current five models use electric yaw; that fact does not define their complete signal architecture or control parameters. Start with the electric-yaw system guide for function and the yaw event record guide for a clearly bounded engineering discussion.
Continue the review with Wind Controller Protocols & Register Maps.
Continue the review with Wind Turbine Tip Speed Ratio: Rotor Radius, RPM & Wind Speed.
Continue the review with Wind Project Engineering Documents: Revisions & Review Status.
Extend the angle-convention review with angle wrapping, unwrapping and circular means.
Review yaw backlash and control deadband and yaw cable twist and rotary interfaces when reconciling angle signals with the actual assembly.
General background: NOAA NDBC: Wind direction definitions and measurement units. These references explain industry concepts; they are separate from the applicable MARSTON product and project documents.
Prepare the information for this review.
Use the checklist to organise the project information. Mark unavailable items and retain document references.
| Review item | Information to provide | Purpose |
|---|---|---|
| Wind convention | From or towards; reference north and rotation direction | Interpret the airflow value correctly. |
| Equipment axis | Physical axis, positive end and absolute or relative angle | Establish what the heading represents. |
| Frame conversion | Original definitions and any documented transform | Compare compatible directions. |
| Circular arithmetic | Unsigned or signed difference; wrapping and averaging method | Avoid boundary and sign errors. |
| Record quality | Timestamps, periods, validity and equipment state | Separate actual direction differences from data issues. |
Engineering questions.
Does a 90° wind direction mean air moves east?
Under the meteorological wind-from convention it means air comes from the east and moves towards the west.
Are wind direction and nacelle heading always comparable?
No. Their physical axes, zero references, signs and absolute or relative meanings must first be established.
Why can 350° and 10° differ by only 20°?
Directions lie on a circle. Their shortest separation crosses the zero boundary, rather than travelling through the remaining 340°.
Is the wrapped angle a yaw-motor command?
No. An explanatory angle calculation does not establish the equipment’s control logic, limits or permitted rotation.
Can I average angles with ordinary arithmetic?
Ordinary averaging can fail at the circular boundary. Use the documented circular method and retain the data-quality basis.
Does this guide confirm which sensors MARSTON supplies?
No. Signal availability, sensor configuration and communication details require confirmation for the selected equipment package.
Technical enquiry
Bring your project information to the discussion.
A yaw-angle comparison requires compatible definitions. Share the available information and the equipment scope you want reviewed in a technical quotation.