**Wind-grapher is a powerful
wind data analysis program that reads data files from met**

towers, wind dataloggers etc.

It produces clear and attractive graphs and wind roses, allows for
advanced quality control, and performs many calculations such as wind
shear, turbulence intensity, extreme wind speeds, and wind turbine energy
production.

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## Data Files

**Wind-grapher reads a
wide variety of data files and formats such as:**

- the date format

- wind speed

- wind direction

- standard deviation

- temperature

Wind-grapher can handle any number of wind speed and direction sensors at
any heights above ground, and any number of gaps or missing values. It can
accept any time step between one minute, and six hours.

## Graphs

**Once you have opened
your data set, you can get straight to analyzing it. wind-grapher produces
many graphs and tables to help you visualize and describe the data. The
time series graph, for example, lets you zoom in on any subset of the
data, scroll forwards or backwards in time, and add or remove any data
column with a single click:**

**Other graphs include
average daily profiles, frequency histograms, and scatterplots of measured
data or of calculated quantities such as air density or wind shear power
law exponent. Examples appear below. In each case, you can choose to plot
all available data, or just a particular year or month. You can export any
graph to a metafile, bitmap, or PNG file.**

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Wind Roses

**Wind-grapher also
produces many types of wind rose diagrams. You can plot the frequency with
which the wind blows from each direction sector, the mean value per
direction sector of any data column, the total amount of wind power per
direction sector, and even polar scatterplots. Some examples appear below.
As with other types of graphs, you can choose to plot the entire data set
or just a particular year or month. You can also choose to display twelve
wind roses simultaneously, one for each month of the year or for each
two-hour segment of the day. You select the number of direction sectors,
and the wind roses update in real time.**

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Wind Shear Analysis

**The Wind Shear Analysis
window displays the vertical wind speed profile and the best-fit wind
shear parameters versus time of day, month, and direction sector:**

## Turbulence Analysis

**The Turbulence Analysis
module calculates turbulence intensity and shows how it varies with wind
speed, wind direction, year, and month. It also allows you to compare the
turbulence in your data set with the standard IEC turbulence categories.**

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Tower Shading Analysis

**The Tower Shading
Analysis window plots the ratio or the difference between two anemometers
by direction, so that tower shading effects become apparent:**

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Extreme Wind Analysis

**If your data set
extends over several years, wind-grapher"s Extreme Wind Analysis module
can calculate the best-fit Gumbel distribution to predict the maximum wind
speed expected within a 25-year, 50-year, or 100-year return period.**

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## Quality Control

**The new Quality Control
window allows you to find and fix problems in the data set, such as the
icing events shown below. You can search for problems by scrolling through
the time series graph and inspecting the data visually, or you can define
formal search rules. You might define a search rule to find, for example,
instances where two anemometers differ by more than 20%, or where the
temperature goes below 0°C and the standard deviation of the wind speed stays below 0.1 m/s for two hours at a time. You can delete problem data
segments, and optionally fill the resulting gaps with synthetic data.**

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Wind Turbine Output

**The Wind Turbine Output
window calculates the expected gross and net energy output and capacity
factor of a wind turbine in the measured wind regime. In making these
calculations, wind-grapher accounts for the effects of varying wind shear
and air density.**

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Gap Filling

**Wind-grapher can also
fill gaps in the data set using an innovative Markov algorithm that takes
the diurnal pattern into consideration. This technique can reliably fill
gaps up to several days in length, not only in wind speed data, but in
wind direction or any other type of data as well. The graph below shows
the synthetic data wind-grapher generated to fill a three-day gap in wind
speed and temperature data:**

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