Combine Anemometers Window

This window lets you combine colocated wind speed sensors. To access this window, choose Revise > Combine Anemometers from the menu. Windographer enables this menu item if the dataset contains at least one pair of visible colocated wind speed sensors.

Meteorological towers used in the wind energy industry often employ two anemometers at each measurement height, with different boom orientations so that at all times at least one is exposed to the wind and free from the effects of tower shading. The Flag Tower Shading window can quickly flag the shaded wind speed values, and this window can combine each pair of flagged data columns into a single calculated column.

You can create your own calculated data columns to combine colocated wind speed sensors, but this window can save time by doing that automatically. For each pair of colocated speed sensors it performs the following steps:

It creates a calculated column to combine the mean wind speeds, and sets the data type and the measurement height of that calculated column.
If both sensors have associated SD columns, it creates a second calculated column for the combined SD values, and associates it with the combined mean speed column.
If both sensors have associated maximum columns, it creates a third calculated column to combine the maximum speeds, and associates it with the combined mean speed column.
If you choose to hide the original data columns, it hides the original data columns along with their associated SD, min, and max columns.

Tip: You can see and edit these calculated columns in the Configure Dataset window.

You can choose among four different approaches to combining anemometers:

Combination Option	Description
Average	The combined value is the average of the two original values when both are valid, or equal to the valid one when only one is valid. It will contain a gap in time steps for which neither original value is valid.
Primary-Backup	The combined value is equal to the primary value whenever it is valid, or the backup value otherwise.
By Boom Orientation	The combined value in each time step is equal to that reported by the anemometer whose boom orientation is nearest to optimal. You define the optimal boom offset, which is the difference between current wind direction and boom orientation.
Reconstruct and Average	The combined speed is the average of the two original speeds when both are valid, but when only one is valid it first reconstructs the other speed using a sector-wise linear regression between the two anemometers, then averages that with the valid speed.

Additional Considerations

The list of colocated pairs excludes calculated columns. But you can combine calculated columns from the Configure Dataset window.

Windographer can consider sensors colocated even if they do not share exactly the same measurement height. You can set the allowable vertical separation in Tools > Options > General.

The Tables window shows statistical summaries of the combined wind speed columns and the original wind speed columns from which they are calculated.