SoDAR Verification Test - Vaisala · 2018. 7. 20. · The verification analysis is based on the IEC...

SoDAR Verification Test Triton SoDAR at Test Site Lelystad

05.03.2015– 29.05.2015

- Confidential –

ECOFYS WTTS B.V.

Kanaalweg 15G | 3526 KL Utrecht| T +31 (0)30 662-3827 | E [email protected] | I www.ecofyswtts.com

Chamber of Commerce 24468357

SoDAR Verification Test Triton SoDAR at Test Site Lelystad

05.03.2015– 29.05.2015

- Confidential –

Project number:

Author:

WIEWT15389

Federico Montealegre

14/07/2015

Reviewer: Anthony Crockford 21/07/2015

Approval: Erik Holtslag 22/07/2015

Filename 20151116_REP_Triton_SoDAR I_VER_MM01_Final

Pages 47

Version Date

Author

Checked

by

Approved

by

Remarks/Change

0.1 27/07/2015 FMo ACr EHo Draft for client review

1.0 03/12/2015 FMo ACr Eho Final

© Ecofys WTTS 2015 by order of: Vaisala Inc.

ECOFYS WTTS B.V.



Summary

On request of Vaisala Inc., Ecofys Wind Turbine Testing Services (WTTS) carried out a verification of a

Triton SoDAR (Triton SoDAR I, Serial number 604) against the reference met mast TSL-MM01 at the

WTTS Test Site Lelystad (TSL).

The 120 m TSL-MM01 is fully IEC and MEASNET compliant and equipped with high quality cup-

anemometers at 40, 80, 100 and 120 m. In addition, wind vanes for wind direction measurements are

located at 87 and 118 m. The SoDAR was collecting wind data at four common heights with the met

mast. The SoDAR verification campaign lasted from 05/03/2015 to 29/05/2015.

All measured data was collected at the specified location and filtered to ensure entirely valid datasets.

The verification analysis is based on the IEC standard 61400-12-1 (ed 2, draft [2]). The Triton SoDAR

604 verification test covers a full three months of collocated measurements during spring and summer

2015, and has permitted the collection of over 5,000 concurrent valid data points. This resulting dataset

is significantly larger than the minimum required, providing a robust basis for uncertainty calculations

in each of the 0.5m/s wind speed bins up to 16 m/s and demonstrates the SoDAR’s performance across

seasons.

Linear regression between the overall SoDAR and met mast recordings showed consistent, highly-

correlated measurements with slopes near unity. The calculated uncertainty in the SoDAR wind speed

measurements is low, in line with first-class anemometry for the majority of the wind speed bins. The

calculated uncertainty tables (in Appendix C) can be used directly in wind resource assessments,

together with the classification uncertainty and site-specific uncertainty components.

Sensitivity tests of the wind speed deviation revealed that the wind speed deviation shows no significant

linear correlation to external conditions: vertical wind speed, horizontal wind speed, turbulence

intensity or rain. This indicates that the SoDAR is insensitive to these factors.

The SODAR measurements were also validated against NORSEWiND criteria for LiDAR remote sensors

[3] and meets the Ecofys WTTS acceptance thresholds for field measurements. There is scatter in the

individual recordings, which is partly due to the distance between the SoDAR and mast during the test.

The overall high correlations and very good linear regression fit indicate that the SoDAR is functioning

properly with high accuracy.

As a result of this test, Ecofys WTTS judges that the SoDAR Triton 604 is suitable for field

measurements. The SODAR will measure the long-term mean wind speeds with accuracy comparable

to cup anemometry in flat terrain. However, when analysing Triton data sets, due consideration should

be made for the standard deviation of 10-minute values characteristic to the system.

ECOFYS WTTS B.V.



Table of contents

1 Introduction 5

1.1 Scope of the study 5

1.2 IEC 61400-12-1 (ed 2) 5

1.3 NORSEWInD verification criteria 6

1.4 Structure of the Report 7

2 Verification Campaign 8

2.1 Site description 8

2.2 Reference IEC-compliant Met Mast description “MM01” 9

2.3 SoDAR Location 10

2.4 SoDAR Orientation and Time Synchronization 11

2.5 Valid wind direction sectors 12

3 SoDAR Verification Procedure 15

3.1 Met Mast Data Filtering 15

3.2 SoDAR Data Filtering 15

3.3 Statistical tests 16

4 Results & Discussion 19

4.1 Data coverage 19

4.2 Wind speed verification 21

4.3 Wind direction verification 23

4.4 Sensitivity tests 26

4.5 Verification uncertainty analysis 27

4.6 NORSEWInD criteria validation 30

5 Conclusions 31

Appendix A Anemometer calibration certificates 33

Appendix B Uncertainty analysis 37

Appendix C Detailed uncertainty analysis 41

WIEWT15389 – Triton SoDAR 131676 Verification 5

1 Introduction

Ecofys WTTS verified the operation of the Triton SoDAR with serial number 604, prior to its application

in a wind measurement campaign. The Triton SoDAR 604 is verified against a fully IEC- and MEASNET-

compliant met mast (120 m) at the Ecofys Test Site Lelystad (TSL). A complete and detailed

assessment of the SoDAR verification process is presented with special attention to sensitivity tests

and uncertainty.

1.1 Scope of the study

This study verifies the accuracy of the Triton SoDAR with serial number 604, and determines whether

it operates as specified by the manufacturer to ensure that the SoDAR measurements from this unit

are traceable to international standards for use in wind resource assessments. The verification

procedure evaluates the accuracy of the SODAR measurements based on two international wind

industry standards:

IEC 61400-12-1 verification procedure and uncertainty evaluation [1] [2]

NORSEWInD SoDAR validation criteria [3]

1.2 IEC 61400-12-1 (ed 2)

IEC 61400-12-1 (ed 1 [1]) is the definitive industry-wide standard for high-quality wind measurement

campaigns using standard anemometry. The second edition (IEC 61400-12-1 (ed 2)*) also specifies

the use of SoDAR, with a detailed procedure (Annex L) that ensures the traceability of the

measurements and evaluates associated uncertainty components, which can be applied in wind

resource assessments:

“This test is a comparison of the remote sensing device measurements to those from calibrated cup

anemometers mounted on a mast spanning a significant portion of the height range of interest. The

purpose of this test is to convey traceability to international standards to this particular device, in the

form of an uncertainty. A second result of the verification test is an assessment of the random noise of

the device.” [2]

The systematic uncertainties in the SoDAR measurements are evaluated for each 0.5 m/s wind speed

bin from 4-16 m/s:

“The standard uncertainty of the reference sensor”;

“The mean deviation of the remote sensing device measurements and the reference sensor

measurements”;

“The standard deviation of the measurement of the RS device calculated as the standard

deviation of the measurements divided by the square root of the number of data per bin”;

“Uncertainty of the remote sensing device due to mounting effects”; and

“Uncertainty of the remote sensing device due to non-homogenous flow.” [2]

* Since the second edition is not yet published, the analysis is based on a Committee Draft [2]


The wind speed dataset should include at least 3 pairs of valid measurements in each wind speed bin

between 4 m/s and 16 m/s, and the total amount of valid data should be minimum 180 hours. For

practical reasons, Ecofys WTTS normally limits the verification campaign to a period of 8 weeks, which

should be sufficient to meet these criteria.

Wind direction measurements are validated in 5 degree bins by means of regression analysis between

SoDAR and met mast wind vane measurements.

1.3 NORSEWInD verification criteria

The IEC procedure does not establish thresholds for the accuracy of the SoDAR measurements; for this

reason, Ecofys WTTS also applies the validation criteria from the EU NORSEWInD project. Even though

these criteria were designed for LiDAR, it is used in this analysis as a reference, as these criteria are

used throughout the wind industry. These criteria can also be evaluated with a shorter campaign so

the SoDAR can be re-validated prior to each measurement campaign – with a comparison to these

results.

NORSEWInD has defined validation criteria to evaluate the absolute error and the quality of the linear

regression between Remote Sensors and anemometry:

“Absolute error – difference in reported wind speed between the reference and test instrument

based on 10-minute averages”;

“Linear regression gradient – this is based on a single variant regression, with the regression

analysis constrained to pass through origin (y=mx+b; b==0)”; and

“Linear regression R-squared values – is the quality of fit value returned from the analysis

performed to assess the linear regression gradient value.” [3]

The NORSEWInD criteria recommends at least 600 valid data points. As noted above, Ecofys WTTS

limited the verification campaign to a period of 12 weeks max., which was sufficient to gather these

600 valid data points. If necessary, the analysis may be based on a smaller sample; to maintain an

accurate comparison, a minimum of 200 valid data points is needed.

The validation criteria are shown in Table 1. The primary comparison will be between measurements

at the top measurement height of the met mast.

If sufficient valid data is collected within the measurement period, the data will also be compared in

two wind speed ranges. This can help to identify non-linearities.

Table 1: NORSEWInD Criteria [2]

Criteria NORSEWInD Threshold

Absolute error <0.5m/s Not more than 10% of data to exceed this value

Linear regression slope Between 0.98 and 1.01

Linear regression R² >0.98


If the SODAR is compliant with the NORSEWInD thresholds, Ecofys WTTS will deem that the unit can

be used for field measurements as a replacement to a met mast, while maintaining a similar level of

accuracy to IEC-compliant cup anemometry.

Ecofys WTTS recognises that there can be a wide range of other purposes for wind measurements with

remote-sensing devices, and also that the NORSEWInD criteria were designed for LiDAR evaluations,

where the device can be located directly at the mast base, which is not possible for SoDARs. Thus,

Ecofys WTTS considers modified thresholds to determine if the unit is suitable in general for field

measurements. These thresholds consider only the overall linear regression and allow for a slightly

wider tolerance. The threshold levels are shown in Table 2. The primary comparison will be between

measurements at the top measurement height of the met mast.

Table 2: Ecofys WTTS Acceptance Thresholds, based on NORSEWInD criteria [2]

Criterion Category

NORSEWInD Acceptance

Threshold for Replacement of IEC-compliant Cup Anemomery

Ecofys WTTS

Acceptance Threshold for Field Measurements

Number of valid data points

4-8m/s >200

8-12 m/s >200

ALL >600

Percentage of data points that exceed 0.5 m/s absolute error

ALL <10% n/a

Linear regression slope

4-8m/s 0.98-1.01 n/a

8-12 m/s 0.98-1.01 n/a

Variation in slope

<0.015 n/a

ALL 0.98-1.01 0.98-1.02

Linear regression – R2

4-8m/s >0.98 n/a

8-12 m/s >0.98 n/a

ALL >0.98 >0.95

1.4 Structure of the Report

First, Test Site Lelystad is described in detail including its surroundings, wind turbines, met masts,

obstacles and orography. Moreover, the SoDAR verification process is designed based on the met mast

layout, instrumentation, valid wind sectors and time synchronisation.

Subsequently, the verification procedure is described. Data filtering and data quality are defined and

summarised and statistical methods are explained. Results for wind speed and wind direction are

presented in the ‘Results and discussion’ chapter including a small discussion subsection per variable.

This chapter also covers on data filtering, NORSEWInD verification criteria and Ecofys WTTS’ SoDAR

thresholds, a sensitivity analysis and an uncertainty analysis. Finally, conclusions are drawn.


2 Verification Campaign

2.1 Site description

Test site Lelystad is located in a flat, open landscape in the centre of the Netherlands with meadows,

scattered houses and several wind turbines nearby. Within a 4 km radius of the site, the terrain does

not vary more than 1.6 m (from 2.9 to 4.5 m below sea level [4]). Including the water level in the

canals, which is about 2 m lower than surrounding land, the slope in the region never exceeds 2% and

all positions at Test Site Lelystad are fully compliant with the IEC 61400-12-1 Terrain Assessment [1].

Figure 1: Terrain at TSL. TSL-MM01 is located to the northwest of wind turbine WTG01 (it is shown as a red triangle).


2.2 Reference IEC-compliant Met Mast description “MM01”

The verification is carried out against the fully IEC compliant instruments on the TSL-MM01 met mast,

whose location is specified in Table 3.

Table 3: Coordinates of met mast TSL-MM01

Easting [RD] Northing [RD]

Met mast TSL-MM01 168,522 504,345

The instrumentation used for this verification is specified in Table 4.

Table 4: Partial sensor list of met mast TSL-MM01

Sensor Height Location Position

(orientation) Sensor type

Serial

Number*

DKD

Calibration

number

Anemometer A1

120 Top

anemometer N/A

Thies TFC adv.

0609242 1436778

Anemometer A2

100 Double boom 349° Thies TFC

adv. 0609153 1436791

Anemometer A3

80 Double boom 169° Thies TFC

adv. 0408875 1436775

Anemometer A4

40 Single boom 169° Thies TFC

adv. 0408870 1436774

Wind Vane WF1

118 Single boom 351° Thies TFC 06131639 /

Wind Vane WF2

40 Single boom 349° Thies TFC 08141535 /

One top anemometer is installed at 120 m next to a lighting protection rod. The lightning rod is about

5 m tall at a distance of 1.3 m from the top-anemometer, as shown in the drawing below. The support

boom of the lightning rod is oriented towards 150°. This design of the lightning detector ensures limited

flow distortion of the top-anemometer recordings according to specifications in [1].

Figure 2: Top-section of TSL-MM01 with top anemometer, wind vane and the lightning rod.

* Serial numbers are used as reference to the calibration certificates from Deutsche Windguard, shown in Appendix A.


The lower anemometers and wind vanes are mounted on booms that are designed according to the IEC

standard 61400-12-1 (edition 1) such that flow distortion is minimised [1].

The mast and some of the instruments (WF1) were installed on MM01 on 18/07/2013. In January and

February 2015, this met mast was equipped with a parallel measurement system with additional

instruments. On 24/02/2015, the refurbished MM01 was commissioned. All new anemometers were

calibrated at the wind tunnel facility of Deutsche WindGuard, Germany in November 2014. All

calibration certificates can be found in Appendix A. The uncertainty in wind measurements is minimised

through the selection of high-quality, calibrated instruments.

For the current test, the wind direction recordings from both the wind vane at 118m and 40m were

used and assigned to the closest measurement height of the cup-anemometers. Other instruments

include a rain sensor, temperature sensor, humidity sensor and a barometer.

2.3 SoDAR Location

The SODAR was installed by personnel from Vaisala Inc. at a test position at a distance of approximately

142 m to the WNW of the TSL-MM01 met mast, as specified in Table 6 and shown in Figure 3. Details

of the installation are presented in a separate report by Ecofys WTTS. The SoDAR was configured to

record wind speeds at 30, 40, 50, 60, 80, 100, 120, 140, 160, 180, and 200 m (above ground level),

which match the measurement heights of the met mast, as well as a number of other heights (not

included in this verification analysis).

The mean horizontal wind speed, mean wind direction were provided for each 10 min period at each

height. Moreover, the mean vertical wind speed and a quality column within a 10 min time interval for

each height were also recorded and provided.

Table 5: Details of the SODAR during verification campaign

Parameters Triton SoDAR 604

Test ID Triton SoDAR I

System serial number 604

Measurement range 40-200 m above ground level

Beam angles 11.5°

Timestamp interval 10 min

Timestamp UTC

Data period 05/03/2015 to 26/05/2015

Data columns recorded

Mean horizontal wind speed, Mean wind

direction, Mean vertical wind speed, TI Quality,

Quality


Table 6: Coordinates of Triton SoDAR 604 measurement position

SODAR ID Longitude

[WGS84]

Latitude

[WGS84]

Easting

[RD]

Northing

[RD]

Triton 604 52.527061 E 5.584502 N 168,390 504,397

Figure 3: Triton SoDAR 604 deployed at Ecofys WTTS test site with view of TSL-MM01 142 m away.

2.4 SoDAR Orientation and Time Synchronization

The Triton SoDAR 604 was oriented towards the North (shown in Figure 4), so no offset was applied in

post-processing. It is synchronised to the Coordinated Universal Time (UTC) every day via GPS clock

and the timestamps correspond to the end of the ten-minute average. In the met mast data acquisition

system, the system clock is synchronised with a NTP time server 5 minutes before every hour. In this

way, the Triton SoDAR’s time series and the mast data’s time series can be examined and adjusted to

line up correctly and ensure that time offset between the SoDAR and met mast is always within 6

seconds, in agreement with IEC standards.


Figure 4: Looking North over the Triton SoDAR I during its deployment. It was installed with 0° offset to the

magnetic north.

2.5 Valid wind direction sectors

Ecofys WTTS performed a Site Assessment investigation and internal report for the Triton’s SoDAR

position in reference with the met mast TSL-MM01 at Test Site Lelystad, in accordance with the

requirements of IEC 61400-12-1 regarding power performance measurements [1]. This analysis was

done before the start of the measurements to ensure that the location could provide adequate

conditions for the test: provision of a sufficiently large sector with predominant winds, and away from

obstacles that could interfere with the SoDAR measurement techniques.

The Obstacle Assessment has shown that some wind direction sectors must be excluded due to the

influence of neighbouring wind turbines. Three TSL wind turbines are operational to the southeast of

the met mast (WTG 1, 3 & 4), so the south-eastern sector is excluded. A row of wind turbines to the


north (partly TSL, partly commercial) results in a large excluded sector as well. The excluded sectors

are shown in the figure below.

Figure 5: Excluded Sectors for TSL-MM01 and co-located SoDAR position, due to surrounding wind turbines (no other

significant obstacles); each colour represents a different wind turbine

Based on this Obstacle Assessment, the primary remaining valid sector for IEC-compliant wind

measurements is from the south-west and a smaller sector to the west, as shown in Figure 6.

Table 7: Excluded wind sectors for Triton SoDAR 604 Verification at test position

Obstacles at TSL Sector minimum [°] Sector maximum [°] Width of excluded sector [°]

Neighbouring wind turbines

0 71 71

106 189 83

286.5 360 73.5

Forests, building or power pylons

0 0 0

Mast shadowing of anemometry

The top anemometer (120 m) will not be affected by mast shadow, but is influenced by the lightning

rod. By comparison of wind speed measurements at lower heights, it was determined that the lightning

rod affected wind sectors from 140-180°. The boom-mounted anemometers will experience mast

shadowing for southerly winds. A comparison of wind speed ratios found influenced wind sectors from

160-190° (and 330-10° for V3).

Wakes of reference met mast on the measurements of the SoDAR

An additional data filter is applied to exclude more sectors influenced by the wakes of the met mast or

the neighbouring wind turbines. The potential influence of the wakes is investigated by plotting the

ratios of the met mast and the SoDAR measurements as a function of wind direction, as proposed in

[2]. Wind direction sectors with a median ratio of >1.05 or < 0.95 are excluded. In this case, no sectors

were excluded due to this filter.

191725334149576573818997105113

121129137145153161169177185193201209217225233241

249257265273281289297305313321329337345353361

369377385393401409417425433441449457465473481489497505513521529537545553561569577585593601609617625633641649657665673681689697705713


Final valid wind sectors

The remaining valid sectors for the verification of the SoDAR against met mast TSL-MM01 are shown

in the figure and table below.

Figure 6: Valid Sectors for SoDAR position in reference to TSL-MM01 at Test Site Lelystad

The selection of this SoDAR position enabled the use of the sectors showed above, while keeping the

distance to the closest nearby turbines more equal and more than 330 m away. The distance to Mast

was calculated to be of 142.5 meters, which supported the informal practical criteria “SoDAR distance

= height of the mast + 20 m”.

Table 8: Valid Wind Direction Sectors for SoDAR Verification Measurement for TSL-MM01

Sector

minimum [°]

Sector

maximum [°]

Width of Sector [°]

E 71 106 35

S-NW 189 286.5 97.5


3 SoDAR Verification Procedure

The SoDAR data will be compared to the met mast data on the basis of 10 minute averages.

To increase the accuracy and repeatability of the verification test, the datasets are filtered according

to the criteria described below. The filtering is carried out in Windographer using flag rules to disable

data.

The filtered data forms the basis for the data analysis, based on the IEC 61400-12-1 verification

procedure and uncertainty evaluation [1] [2] and NORSEWInD SoDAR validation criteria [3]. All data

analyses techniques are described in Section 3.3, and are performed in Excel.

3.1 Met Mast Data Filtering The met mast dataset is filtered according to the following protocols:

3.1.1 System non-availability

This category covers power outages, maintenance and other external issues. During these periods, no

data is recorded, so data does not need to be flagged or disabled. This category is defined to explain

any missing data due to external issues.

3.1.2 Wind direction recordings

Wind direction measurements are not available at all heights. Therefore, Wind Vane WF1 (at 118 m) is

linked to wind speeds of 80, 100 and 120 m. Wind Vane WF2 (at 40 m) is linked to wind speeds at 40

m.

3.1.3 Icing of instruments

During sub-zero temperatures, all met mast instruments including cup-anemometer data will be

checked for icing by inter-comparison with other heights and checks for constant output during frost.

In case suspicion of icing exists, all data will be disabled and flagged as ‘Outside operational envelope’.

3.1.4 Excluded wind sectors

All excluded sectors are filtered out, according to the valid sectors identified in Section 2.5. This

category combines mast shadowing of mast instrumentation and disturbed sectors. All wind data is

disabled if either wind vane is within an excluded sector, and flagged as ‘Excluded sectors.’

3.2 SoDAR Data Filtering

The SoDAR dataset is filtered according to the following protocols:

3.2.1 System non-availability

This category covers power outages, maintenance and other external issues. During these periods, no

data is recorded, so data does not need to be flagged or disabled. This category is defined to explain

any missing data due to external issues.


3.2.2 Excluded wind sectors

All wind data is disable and flagged as ‘Excluded Sectors’ for any time stamp where either met mast

wind direction is within excluded sectors.

3.2.3 Conditions outside operational envelope

A SODAR can be disturbed by strong noise or weather conditions such as heavy snow. These periods

would be marked as “outside operational envelope”. The client provided vertical wind speed criteria to

account for invalid points due to precipitation, which was assigned to this filter.

3.2.4 Wind Quality Factor - Low signal to noise conditions

The wind quality factor is embedded in the acquisition of the SoDAR measurement data and is a function

of the signal to noise ratio and the number of valid samples collected for every 10 minute interval. It

is used to filter noisy wind data and as per manufacturer’s recommendation all timestamps where the

quality factor values are less than 90% were filtered out.

3.2.5 Turbulence Intensity Quality Factor

Since the vector wind speed is inversely proportional to the turbulence intensity estimation, high TI

values are produced at low wind speeds. In the Triton SoDAR 604 a turbulence quality factor was

defined to eliminate invalid turbulence measurements from the data set in low wind speed conditions

e.g. >3.5m/s. As per manufacturer’s recommendation, this column and all TI Quality values < 90%

were filtered out.

3.2.6 Vertical wind speed filter criteria

During rain, the Triton SoDAR 604 can interpret the falling raindrops or snowflakes as a strong vertical

wind and, as a result, the measured wind speed can be incorrect. Filtering vertical wind speeds > +/-

1.5 m/s removes any data affected by precipitation.

3.2.7 Data processing issues

Data is disabled in the event the data processing software fails to remove erroneous data.

3.3 Statistical tests

A number of statistical methods are applied to the filtered datasets, based on the requirements of IEC

61400-12-1 [2].

3.3.1 Scatter plot

The measurements of the SoDAR are plotted against the measurements of the reference anemometer,

also showing the deviations between the SoDAR and reference anemometer. The wind speed deviation

is defined as the deviation between SoDAR and met mast mean wind speeds at the same height. The

mean deviation and standard deviation of deviations is also calculated.

3.3.2 Bin averaged analysis

A bin averaging procedure is used to compare the SoDAR measurements and the reference

anemometers, using wind speed bins of 0.5 m/s between 4-16 m/s. The bin-wise deviation between

the SoDAR and reference measurements is the key result. Each wind speed bin should contain at least

3 valid pairs of data to ensure a representative SoDAR verification [2].


Linear regression analysis is applied in order to evaluate the relationship in terms of horizontal mean

wind speed and mean wind direction with zero and non-zero constants at each height. Also the

coefficient of determination (R²) of the linear regression is given. Below, the formulae are given for

each parameter that is analysed.

Two-parameter linear regression

The two-parameter Ordinary Least Squares regression equation is:

kxCy

Coefficient of determination

The coefficient of determination (R²) of the linear regression is calculated as:

tot

err

SS

SSR 12

2

i

iierr fySS

2

i

itot yySS

where if is the modelled value and y is the mean of the observed data.

Wind speed deviation

The mean and standard deviation of the wind speed deviation is also calculated for each wind speed

bin of 0.5 m/s.

3.3.3 Wind direction

Similarly, a bin averaging procedure is used to compare the SoDAR wind direction measurements and

the reference wind vanes, using wind direction bins of 10° (based on the test uncertainty shown in

Section 2.2). A two-parameter Ordinary Least Squares linear regression is used, in order to identify

any offset from zero.

3.3.4 Sensitivity tests

Several sensitivity tests are run to find any possible relationship with external conditions, including

SoDAR vertical wind speed, met mast mean wind speed, turbulence intensity and precipitation.

3.3.5 Uncertainty analysis

After all sensitivity tests and statistical analyses, Ecofys analyses the uncertainty of the wind

measurements of this SoDAR. The uncertainty calculations are based on IEC 61400-12-1 (ed 2) which

is still in draft [2]. If information is absent in the draft, formulae and definitions were taken from the

first edition [1].

The uncertainty resulting from the SoDAR verification test is divided into 5 separate uncertainties, as

summarised below:

1. Reference uncertainty (in anemometry)

a. Wind tunnel calibration


b. Cup anemometer effects according to the anemometer classification

c. Cup anemometer mounting effects

i. Mast shadowing

ii. Boom distortion

iii. Lightning rod distortion

d. Uncertainty of any applied mast correction

2. Mean deviation of the SoDAR measurements and the reference anemometry measurements

3. Standard deviation of the measurement of the SoDAR

4. Uncertainty in mounting effects during the verification test

5. Uncertainty of the SoDAR due to non-homogeneous flow within the measurement volume,

during the verification test

The uncertainties are combined as the square root of the sum of squares:

𝑈𝑡𝑜𝑡𝑎𝑙 = √𝑈12 + 𝑈22 + 𝑈32 + 𝑈42 + 𝑈52

The calculated uncertainty refers to the uncertainty in the performance verification test. The total

uncertainty for future wind measurement campaigns will also include components relating to site-

specific mounting and flow condition on-site, and uncertainty resulting from the classification of the

SoDAR (sensitivity to environmental variables). These uncertainties should be assessed as part of the

wind resource assessments.

3.3.6 NORSEWInD criteria

Some additional statistical tests are performed to compare with the NORSEWInD criteria [3].

The linear regression, including coefficient of determination, is re-calculated for three different wind

speed ranges without any bin-averaging. First, all wind data is used, then two smaller ranges are

filtered for 4-8 m/s and 8-12 m/s. The slopes of the linear regression fit are compared for the two

smaller ranges, in order to identify non-linearity in the system performance.

Also, the wind speed deviation is assessed in terms of absolute error.

Single-parameter linear regression

The NORSEWInD criteria are based on a single parameter Ordinary Least Squares regression model

according to the following equation:

mxy

y = SoDAR measurement

x = met mast measurement


4 Results & Discussion

The results for the Triton SoDAR 604 verification are presented below. The data coverage is shown,

followed by linear regression of the wind speed and direction measurements. A sensitivity analysis is

shown against several environmental factors. Finally, the verification uncertainty analysis and

validation against NORSEWInD criteria are presented.

4.1 Data coverage

The data filtering (described in the previous chapter) reduced the number of data points by about half,

as seen in Table 9. The disabled data was primarily due to wind directions from excluded sectors, as

well as some SoDAR data that was flagged as per filters described above in Chapter 3.

Table 9 : Number of data points and data coverage before and after filtering for the Triton SoDAR 604.

Height [m]

Number of data points

Before filtering After filtering

SoDAR Met mast SoDAR Met mast

40 12,048 12,241 5,130 6,244

80 12,048 12,241 5,477 6,335

100 12,048 12,241 5,512 6,335

120 12,048 12,241 5,508 6,335


Time series of the valid data, in terms of mean wind speed, wind speed deviation and wind

direction are plotted in the graphs below.

Figure 7. Time series of the Triton SoDAR 604 and met mast mean wind speed at 120m, 100, 80 and 40m.

Figure 8. Time series of the Triton SoDAR 604 and met mast wind speed deviation at 120m, 100, 80 and 40m.

Figure 9. Time series of the Triton SoDAR 604 and met mast mean wind direction at 120m, 100, 80 and 40m.

0

5

10

15

20

25

30

21/02/2015 07/03/2015 21/03/2015 04/04/2015 18/04/2015 02/05/2015 16/05/2015 30/05/2015 13/06/2015

Mean

win

d s

peed

[m

/s]

Vmean SoDAR 120m

Vmean met mast 120m

Vmean SoDAR 100m

Vmean met mast 100m

Vmean SoDAR 80m

Vmean met mast 80m

Vmean SoDAR 40m

Vmean met mast 40m

-4

-3

-2

-1

0

1

2

21/02/2015 07/03/2015 21/03/2015 04/04/2015 18/04/2015 02/05/2015 16/05/2015 30/05/2015 13/06/2015

Win

d s

peed

devia

tio

n [

m/

s]

Wind speed deviation 120 m




0

90

180

270

360

21/02/201507/03/201521/03/201504/04/201518/04/201502/05/201516/05/201530/05/201513/06/2015

Win

d d

irecti

on

Wind direction SoDAR 120 m

Wind direction met mast 118 m

wind direction SoDAR 100 m


wind direction met mast 40 m



4.2 Wind speed verification

The mean wind speed measured by the Triton SoDAR is compared to the concurrent met mast

measurements in a scatter plot (see Figure 10, Figure 11, Figure 12 and Figure 13) and a single

parameter “Ordinary Least Squares” (OLS) linear regression is applied. The slope of the linear

regression and the corresponding coefficients of determination (R²) are shown. The plots show a very

good correlation between the SoDAR and met mast wind speed measurements.

The wind speed deviation is defined as the SoDAR mean wind speed minus the met mast mean wind

speed. This is also plotted (in m/s) in the scatter plots below. The statistical distribution of the wind

speed deviations has been derived, as shown in Table 10.

Figure 10: Linear regression of mean wind speed at 120m for the Triton SoDAR 604.



Table 10: Statistical parameters of wind speed deviation for each reference height for Triton SoDAR 604.

Height [m]

Mean of Wind Speed

Deviations

[m/s]

Standard Deviation of

Wind Speed Deviations

[m/s]

40 0.025 0.525

80 0.023 0.476

100 -0.020 0.434

120 -0.020 0.452

4.3 Wind direction verification

Similarly, a linear fit is applied to scatter plots of the wind direction, as shown in Figure 14 through

Figure 17. A two-parameter Ordinary Least Squares linear regression is used, in order to identify any

offset from zero, with slopes, offsets and coefficients of determination (R²) plotted in the graphs.

The correlation between SoDAR and met mast binned wind directions is excellent, with a slope very

close to unity and an offset of approximately +3° which is within the mounting uncertainty of the

SoDAR and wind vanes. Thus, there is no apparent offset and hence none has been corrected for.


Figure 14: Linear regression of mean wind direction at 120m for the Triton SoDAR 604.



4.4 Sensitivity tests

Several sensitivity tests are run to find any possible relationship with external conditions. The wind

speed deviation at 120 m is plotted against SoDAR vertical wind speed, met mast mean wind speed,

turbulence intensity and precipitation, as seen in Figure 18. The plots show negligible correlation,

indicating that filtered SoDAR data is insensitive to vertical wind speed, mean wind speed, turbulence

intensity or rain. Most periods with any precipitation are efficiently identified and filtered out (as well

as larger vertical wind speeds) with the SoDAR filters.

a) SoDAR vertical mean wind speed

b) Reference wind speed

c) Turbulence Intensity

d) Wind speed deviation against precipitation

Figure 18: Sensitivity tests of wind speed deviation at 120m plotted against other factors, for the Triton SoDAR 604.


4.5 Verification uncertainty analysis

For each height an uncertainty analyses was applied to each wind speed bin of 0.5 m/s between 4 and

16 m/s. For the all bins, a sufficient number of valid data points were collected. A detailed overview

table can be found in Appendix C.

This analysis shows low uncertainty in the SoDAR wind speed measurements, in line with first class

anemometry. The uncertainty is increased at higher wind speed bins, partly due to relatively fewer

data points. The uncertainty levels are higher for the 40 meters measurement height, due to the

formula for the uncertainty due to variation in flow across the site, which is a function of the

measurement height and the distance between the SoDAR and mast (see Appendix B).

The calculated uncertainty can be used directly in wind resource assessments with this device, together

with the classification uncertainty and site-specific uncertainty components.

Figure 19: Uncertainty analysis of SoDAR wind speed measurements at 120 m for the Triton SoDAR 604.



Figure 21: Uncertainty analysis of SoDAR wind speed measurements at 80m m for the Triton SoDAR 604.


4.6 NORSEWInD criteria validation

The results of the verification campaign are also validated against the NORSEWInD criteria outlined in

Section 1.3. Table 11 shows that this device meets most of the NORSEWInD criteria and all of the

Ecofys WTTS acceptance thresholds for field measurements, which are highlighted in bold, with passing

results highlighted in green, failing results in red and marginal passes shown in yellow. A marginal pass

is a result that deviates from the criteria by a small amount.

The overall high correlations and very good linear regression fit for the entire data set indicate that the

Triton SoDAR 604 is functioning properly, with high accuracy and there are no underlying issues

present. The validation of the Triton SoDAR 604 shows that this device is suitable for field

measurements based on the Ecofys WTTS acceptance thresholds.

Table 11: Criteria analysis for the Triton SoDAR 604.

Citerium Category

NORSEWInD Acceptance Threshold for Replacement

of IEC-compliant Cup Anemometry

Ecofys WTTS Acceptance Threshold

for Field Measurements

120m 100m 80m 40m

Number of valid data points

4-8m/s >200 2,630 2,898 3,168 3,326

8-12 m/s >200 2,064 1,869 1,620 1,134

ALL >600 5,508 5,512 5,477 5,130

Percentage of data points that exceed 0.5 m/s absolute error

<10% n/a 18.8% 17.5% 18.9% 21.9%

Linear regression slope

4-8m/s 0.98-1.01 n/a 1.003 0.999 1.004 1.004

8-12 m/s 0.98-1.01 n/a 0.999 0.999 1.011 1.017

Variation in slope

<0.015 n/a 0.003 0.000 0.008 0.012

ALL 0.98-1.01 0.98-1.02 0.995 0.996 1.000 1.000

Linear regression – R2

4-8m/s >0.98 n/a 0.914 0.918 0.911 0.893

8-12 m/s >0.98 n/a 0.866 0.867 0.841 0.746

ALL >0.98 >0.95 0.975 0.976 0.972 0.965


5 Conclusions

On request of Vaisala Inc., Ecofys Wind Turbine Testing Services (WTTS) carried out a verification of a

Triton SoDAR 604 (Triton with logger number 604) against met mast TSL-MM01 at the WTTS Test Site

Lelystad (TSL).

The 120 m TSL-MM01 is fully IEC and MEASNET compliant and equipped with cup-anemometers at 40,

80, 100 and 120 m. In addition, wind vanes for wind direction measurements are located at 87 and

118 m. The SoDAR was installed 142.5 meters WNW from MM01 and collected wind data at four

common heights with the met mast. The SoDAR verification campaign lasted from 05/03/2015 to

26/05/2015.

All measured data was collected at the specified location and filtered to ensure entirely valid datasets.

The verification analysis is based on the IEC standard 61400-12-1 (ed 2, draft [2]). The Triton SoDAR

604 verification test covers a full three months of collocated measurements during spring and summer

2015, and has permitted the collection of over 5,000 concurrent valid data points. This resulting dataset

is significantly larger than the minimum required, providing a robust basis for uncertainty calculations

in each of the 0.5m/s wind speed bins up to 16 m/s and demonstrates the SoDAR’s performance across

seasons.

Linear regression between the overall Triton SoDAR 604 and met mast recordings showed consistent,

highly-correlated measurements with slopes near unity. The calculated uncertainty in the SoDAR wind

speed measurements is relatively low, in line with high quality anemometry for the majority of the wind

speed bins. The calculated uncertainty tables (in Appendix C) can be used directly in wind resource

assessments, together with the classification uncertainty and site-specific uncertainty components.

Sensitivity tests of the wind speed deviation revealed that the wind speed deviation shows no significant

linear correlation to external conditions: vertical wind speed, horizontal wind speed, turbulence

intensity or rain. This indicates that the filtering techniques recommended by the manufacturer are

precise, and make the Triton SoDAR 604 relatively insensitive to these factors.

The SODAR measurements were also validated against NORSEWiND criteria [3] and meets the Ecofys

WTTS acceptance thresholds for field measurements. There is scatter in the individual recordings, which

may be partly due to the distance between the SoDAR and mast during the test. The overall high

correlations and very good linear regression fit indicate that the SoDAR is functioning properly with

high accuracy.

As a result of this test, Ecofys WTTS judges that the SoDAR Triton 604 is suitable for field

measurements. The SODAR will measure the long-term mean wind speeds with accuracy comparable

to cup anemometry in flat terrain. However, when analysing Triton data sets, due consideration should

be made for the standard deviation of 10-minute values characteristic to the system.


References

[1] IEC 61400-12-1 (ed 1.0), ‘Wind turbines – Part 12-1: Power performance measurements of electricity producing wind turbines’, 2005

[2] IEC, IEC 61400-12-1 Ed. 2 (642/DCV) ‘Committee Draft - Power performance measurements of electricity producing wind turbines’, 2013

[3] Kindler, D., Courtney, M., Oldroyd, A., 2009, 'Testing and calibration of various SoDAR remote

sensing devices for a 2 year offshore wind measurement campaign', EWEC 2009.

[4] Lindelöw-Marsden, P. ‘Upwind D1: Uncertainties in wind assessment with SODAR’. Risø DTU, 2009, Risø-R-1681(EN)

[5] Topographische Dienst, ‘Compact Provincie Atlas 1:50,000 – Utrecht/Flevoland’, 1997

[6] Deutsche Windguard, 2008, ‘Summary of cup-anemometer classification according to IEC 61400-12-1 (2005-12) Classification scheme’, AK081662.01S


Appendix A Anemometer calibration certificates Top cup-anemometer A1 at 120 m


Cup-anemometer A2 at 100 m


Appendix B Uncertainty analysis

As described in Annex L of IEC 61400-12-1 (edition 2 draft) [2], the uncertainty in the SoDAR wind

measurements can be divided into 6 separate uncertainties, as summarised below:

1. Reference uncertainty (in anemometry)

a. Wind tunnel calibration

b. Cup anemometer effects according to the anemometer classification

c. Cup anemometer mounting effects

i. Mast shadowing

ii. Boom distortion

iii. Lightning rod distortion

d. Uncertainty of any applied mast correction

2. Mean deviation of the SoDAR measurements and the reference anemometry measurements

3. Standard deviation of the measurement of the SoDAR

4. Uncertainty in mounting effects at the verification test



6. Uncertainty due to variation in flow across the site

The uncertainties are combined as the square root of the sum of squares:

𝑈𝑡𝑜𝑡𝑎𝑙 = √𝑈12 + 𝑈22 + 𝑈32 + 𝑈42 + 𝑈52

1. Reference uncertainty (Met mast anemometer)

The following uncertainty components are considered for the evaluation of the reference sensor

uncertainty.

1. a) Wind tunnel calibration

The uncertainty in wind tunnel calibration is defined as the root sum square of standard error in linear

fit in the calibration certificates of the met mast and the wind tunnel accuracy. The calibration

certificates for the anemometers at met mast TSL-MM01 can be found in Appendix A.

1. b) Cup anemometer effects according to the anemometer classification

This uncertainty relates to the sensitivity of the cup anemometer to ranges of environmental

parameters per terrain class. Valid ranges of environmental variables are defined for Class A and B in

Annex I of [1], as shown in Table 12. Test Site Lelystad meets all of the criteria of a Class A site, unless

temperatures drop below 0 or turbulence intensity is incidentally exceeding the class A thresholds.


Table 12: Influence parameter ranges (based on 10 min average) of Classes A and B [1]

The sensitivity of several cup anemometer models was calculated in the Deutsche Windguard study

[6]. For a Thies First Class cup anemometer (as used at TSL-MM01), in Class A conditions, the class

number k equals to 0.9, and in Class B conditions (such as periods with temperatures below zero), k is

3.0. This class number k is inserted into the following equation to derive the standard uncertainty due

to cup-anemometer type and environmental conditions during the verification test:

𝑢𝑉2,𝑖 = (0,05 𝑚 𝑠⁄ + 0,005 ∙ 𝑈𝑖) ∙ 𝑘/√3

c) Cup anemometer mounting effects

The cup anemometers are influenced by flow distortion of the met mast’s components:

For the top anemometer: lightning rod distortion ((and interference with each other)

For the cup anemometers below top: mast distortion and boom distortion

Mast distortion depends upon the type of mast and its solidity, the drag of the individual members, the

orientation of the wind and the separation of the measurement point from the mast. Therefore in Annex

G.4 of [2], mast distortion functions are defined for different mast types. Based on met mast design

drawings, met mast TSL-MM01 has a solidity of 0.15 and an R/L (roughly boom length over leg

distance) of 5.2 which results in a Ct of 0.27. Entering these values into the equation below results in

a standard uncertainty of about 0.3% of the measured 10 min wind speed at every time interval.

𝑈𝑑 = 1 − (0.062𝐶𝑡2 + 0.076𝐶𝑡) ∙ (

𝐿

𝑅− 0.082)

The flow distortions due to the booms equals 0.5% as this IEC-compliant met mast was designed such

that its boom distortion is kept below 0.5%.

Lightning rod distortion can be ignored if the following conditions are met [2]:

1. The top cup-anemometer is separated horizontally at least 30 times the lightning rod diameter

from the lightning rod. As separation equals 30.8 times for TSL-MM01, this criteria is met

2. The cup-anemometer is not in the wake of the lightning rod. As the sectors disturbed by the

lightning rod overlap with the excluded sectors, no wind data disturbed by the lightning rod is

in the data set anymore.


d) Uncertainty of any applied mast correction

This uncertainty defines any uncertainties in applied mast corrections. Since no correction factors were

used for the wind speed data, this uncertainty is excluded.

2. Mean deviation of the SoDAR measurements and the reference anemometry

measurements

This refers to the mean deviation of the remote sensing device measurements and the reference sensor

measurements for each bin of 0.5 m/s as defined in Annex L4.2.1 of [2]. The standard uncertainty is

derived from the difference between remote sensing device mean wind speed and met mast mean wind

speed. To obtain a percentage, the standard uncertainty is divided by the met mast mean wind speed.

Therefore the mean deviation uncertainty tends to be higher at lower wind speeds.

3. Precision of the measurement of the SODAR

The precision of the measurement of the remote sensing device calculated as the standard deviation

of the measurements divided by the square root of the number of data per bin as defined in Annex

L4.2.1 of [2].

4. Uncertainty in mounting effects at the verification test

This uncertainty is related to non-ideal levelling of the device and shall be estimated by us according

to Annex L4.5 in [2]. This is assumed to be 0% based on stable foundations for the Ecofys WTTS test

pad.



Considering the homogenous terrain conditions within the valid sectors, this uncertainty component is

considered negligible and therefore set to 0%.

6. Uncertainty due to variation in flow across the site

There is an uncertainty due to variation of flow conditions between the centre of the remote sensing

device and the met mast. According to L4.2.1 in [2], this can be calculated as 1% times the separation

distance divided by the measurement height.


Table 13: Uncertainties for TSL-MM01 used for this SoDAR verification

Uncertainty

category

Uncertainty

subcategory Parameter Value

Reference uncertainty

(in anemometry)

See uncertainty table, defined per wind speed bin of

0.5 m/s

Wind tunnel

calibration

Calibration

standard error

in linear fit

and the wind

tunnel

accuracy for

k=1

Defined per wind speed bin of 0.5%

0.014 m/s (at 120 m) and 0.025 m/s

0.015 m/s (at 100 m) and 0.025 m/s

0.016 m/s (at 80 m) and 0.025 m/s

0.021 m/s (at 40 m) and 0.025 m/s

Cup anemometer

effects according

to the anemometer

classification

k 0.9

Cup anemometer

mounting effects Uncertainty

0% for top anemometer (data possibly affected by

lightning rod distortion are disabled)

0.5% for boom distortion

Uncertainty of any

applied mast

correction

0.0%

Mean deviation of the SoDAR

measurements and the reference

anemometry measurements


0.5 m/s

Standard deviation of the

measurement of the SoDAR


0.5 m/s

Uncertainty in mounting effects

at the verification test Uncertainty 0.0%

Uncertainty of the SoDAR due to

non-homogeneous flow within

the measurement volume,


Uncertainty 0.0%

Uncertainty due to variation in

flow across the site Uncertainty

Defined per height, based on the separation distance

between met mast and remote sensing device:

1.19%s (at 120 m)

1.42% (at 100 m)

1.78% (at 80 m)

3.56% (at 40 m)


Appendix C Detailed uncertainty analysis

Data coverage

During this verification campaign, the met mast was fully available for measurements. The SoDAR was

operating 100% of the time.

Table 14: Logbook of technical issues and external problems of the SoDAR and met mast.

Date and time Duration Issue Details

n/a

The breakdown of the data points flagged by each filtering criteria is shown in Table 15. The same data

point can be flagged for different criteria. Therefore the sum of all criteria exceeds the total number of

data points possible within the measurement period. All flagged data was disabled and excluded from

the verification.

The conditions specific to this verification campaign affect the count of several categories and are

therefore not necessarily representative of the long-term. System non-availability for instance is

affected by external power outages, while low signal to noise conditions are raised due to rain and

strong wakes from wind turbines in disturbed sectors.

Table 15: Number of data points flagged for each filtering criteria for each height. Numbers include double-counts of

data points, as one data point can be flagged for several categories. Environmental conditions at the test site affect

the count of system non-availability (e.g. due to power outages) and low signal to noise conditions (strong wakes

from several nearby wind turbines), which are not representative of a random measurement campaign.

Height [m]

System non-availability

Excluded wind sectors

Low SNR, SoDAR Filters & Met Mast Icing

Data processing issues

Conditions outside

operational envelope & wind speed

intercomparison

40 192 0 5951 5995 2340 0 0 0 0 0

80 192 0 5854 5903 1953 0 0 0 0 0

100 192 0 5854 5903 1897 0 0 0 0 0

120 192 0 5854 5903 1875 0 0 0 0 0

After filtering, all wind speed bins should have at least the required amount of wind data (3 valid data

points per bin). Sometimes certain bins do not meet these criteria. If the two adjacent bins had 3 or

more data points, the overall uncertainty could be interpolated. Otherwise no uncertainty is shown for

the entire wind speed bin.

Uncertainty Analysis

The detailed results of the uncertainty calculations, based on the IEC 61400-12-1 methods, are

presented below. The uncertainty figure in the tables below are based on a coverage factor of 1 which

implies that the level of confidence is 68%.


Table 16 - Uncertainty analysis at 120 m for the Triton SoDAR 604

Bin

Vcu

p

VR

SD

Nu

mb

er o

f

data

sets

VR

SD m

ax

VR

SD m

in

VR

SD-s

td

VR

SD-s

td/√n

Mean

devia

tio

n

Vcu

p

un

certa

inty

Mou

nti

ng

un

certa

inty

Flo

w

un

certa

inty

VR

SD

un

certa

inty

4 4.010 3.975 169 7.60 3.42 0.386 0.030 -0.9% 1.2% 0.0% 1.2% 2.0%

4.5 4.525 4.486 222 6.06 3.31 0.346 0.023 -0.9% 1.0% 0.0% 1.2% 1.9%

5 5.012 4.963 278 6.23 3.77 0.344 0.021 -1.0% 1.0% 0.0% 1.2% 1.9%

5.5 5.501 5.530 312 7.13 4.52 0.392 0.022 0.5% 0.9% 0.0% 1.2% 1.6%

6 5.997 6.053 311 7.81 4.70 0.398 0.023 0.9% 0.8% 0.0% 1.2% 1.8%

6.5 6.496 6.508 324 8.56 5.00 0.376 0.021 0.2% 0.8% 0.0% 1.2% 1.5%

7 6.992 7.014 435 8.19 5.62 0.362 0.017 0.3% 0.8% 0.0% 1.2% 1.5%

7.5 7.496 7.537 440 9.52 6.22 0.406 0.019 0.5% 0.7% 0.0% 1.2% 1.5%

8 7.994 8.005 423 9.74 6.90 0.376 0.018 0.1% 0.7% 0.0% 1.2% 1.4%

8.5 8.494 8.514 352 9.77 6.78 0.379 0.020 0.2% 0.7% 0.0% 1.2% 1.4%

9 8.989 8.961 335 10.79 7.67 0.422 0.023 -0.3% 0.6% 0.0% 1.2% 1.4%

9.5 9.493 9.478 247 11.84 8.28 0.441 0.028 -0.2% 0.6% 0.0% 1.2% 1.4%

10 10.014 9.978 249 11.36 8.11 0.482 0.031 -0.4% 0.6% 0.0% 1.2% 1.4%

10.5 10.482 10.411 240 12.05 7.82 0.511 0.033 -0.7% 0.6% 0.0% 1.2% 1.5%

11 10.985 11.006 214 12.49 9.56 0.527 0.036 0.2% 0.6% 0.0% 1.2% 1.4%

11.5 11.483 11.566 152 13.40 10.54 0.555 0.045 0.7% 0.5% 0.0% 1.2% 1.5%

12 11.990 11.976 141 13.88 10.78 0.584 0.049 -0.1% 0.5% 0.0% 1.2% 1.4%

12.5 12.498 12.513 127 13.96 11.24 0.572 0.051 0.1% 0.5% 0.0% 1.2% 1.4%

13 12.981 12.866 99 14.59 11.79 0.552 0.055 -0.9% 0.5% 0.0% 1.2% 1.6%

13.5 13.507 13.255 61 14.88 12.30 0.549 0.070 -1.9% 0.5% 0.0% 1.2% 2.3%

14 13.986 13.765 75 15.60 10.72 0.804 0.093 -1.6% 0.5% 0.0% 1.2% 2.1%

14.5 14.528 14.372 51 15.97 12.10 0.689 0.096 -1.1% 0.5% 0.0% 1.2% 1.8%

15 14.982 14.750 45 16.27 13.38 0.598 0.089 -1.6% 0.5% 0.0% 1.2% 2.1%

15.5 15.500 15.243 44 16.50 13.84 0.614 0.093 -1.7% 0.5% 0.0% 1.2% 2.2%

16 16.047 15.613 17 17.12 14.42 0.736 0.179 -2.7% 0.5% 0.0% 1.2% 3.2%


Table 17 - Uncertainty analysis at 100 m for the Triton SoDAR 604.

Bin

Vcu

p

VR

SD

Nu

mb

er o

f

data

sets

VR

SD m

ax

VR

SD m

in

VR

SD-s

td

VR

SD-s

td/√n

Mean

devia

tio

n

Vcu

p

un

certa

inty

Mou

nti

ng

un

certa

inty

Flo

w

un

certa

inty

VR

SD

un

certa

inty

4 4.006 3.968 178 4.69 3.32 0.279 0.021 -0.9% 1.3% 0.0% 1.4% 2.2%

4.5 4.497 4.460 263 6.19 3.41 0.331 0.020 -0.8% 1.2% 0.0% 1.4% 2.1%

5 4.995 4.955 283 6.04 3.79 0.330 0.020 -0.8% 1.1% 0.0% 1.4% 2.0%

5.5 5.508 5.506 341 8.85 4.65 0.364 0.020 0.0% 1.0% 0.0% 1.4% 1.8%

6 6.004 5.988 359 7.36 4.82 0.328 0.017 -0.3% 1.0% 0.0% 1.4% 1.8%

6.5 6.506 6.501 425 8.81 5.60 0.363 0.018 -0.1% 0.9% 0.0% 1.4% 1.7%

7 6.997 7.026 485 9.64 5.46 0.396 0.018 0.4% 0.9% 0.0% 1.4% 1.8%

7.5 7.482 7.463 443 8.97 6.16 0.376 0.018 -0.3% 0.9% 0.0% 1.4% 1.7%

8 7.993 8.019 391 10.07 6.88 0.399 0.020 0.3% 0.9% 0.0% 1.4% 1.7%

8.5 8.502 8.489 325 9.74 7.58 0.372 0.021 -0.2% 0.8% 0.0% 1.4% 1.7%

9 8.990 8.906 287 10.14 7.43 0.420 0.025 -0.9% 0.8% 0.0% 1.4% 1.9%

9.5 9.485 9.462 253 11.33 7.87 0.439 0.028 -0.2% 0.8% 0.0% 1.4% 1.7%

10 9.995 9.993 236 11.46 8.57 0.476 0.031 0.0% 0.8% 0.0% 1.4% 1.7%

10.5 10.502 10.508 204 12.52 8.23 0.579 0.041 0.1% 0.8% 0.0% 1.4% 1.7%

11 10.986 11.061 168 12.58 9.84 0.508 0.039 0.7% 0.8% 0.0% 1.4% 1.8%

11.5 11.506 11.497 152 13.41 10.28 0.527 0.043 -0.1% 0.7% 0.0% 1.4% 1.6%

12 11.994 12.077 121 13.81 10.83 0.616 0.056 0.7% 0.7% 0.0% 1.4% 1.8%

12.5 12.499 12.474 100 14.01 11.35 0.549 0.055 -0.2% 0.7% 0.0% 1.4% 1.7%

13 12.981 13.024 52 14.25 11.90 0.547 0.076 0.3% 0.7% 0.0% 1.4% 1.7%

13.5 13.487 13.342 76 15.43 9.85 0.766 0.088 -1.1% 0.7% 0.0% 1.4% 2.0%

14 14.005 13.911 61 16.12 12.35 0.708 0.091 -0.7% 0.7% 0.0% 1.4% 1.8%

14.5 14.474 14.361 46 15.31 12.73 0.581 0.086 -0.8% 0.7% 0.0% 1.4% 1.9%

15 15.005 14.871 48 15.69 13.78 0.468 0.068 -0.9% 0.7% 0.0% 1.4% 1.9%

15.5 15.489 15.223 20 16.05 14.23 0.478 0.107 -1.7% 0.7% 0.0% 1.4% 2.4%

16 15.961 15.513 11 16.72 14.54 0.727 0.219 -2.8% 0.7% 0.0% 1.4% 3.5%



Bin

Vcu

p

VR

SD

Nu

mb

er o

f

data

sets

VR

SD m

ax

VR

SD m

in

VR

SD-s

td

VR

SD-s

td/√n

Mean

devia

tio

n

Vcu

p

un

certa

inty

Mou

nti

ng

un

certa

inty

Flo

w

un

certa

inty

VR

SD

un

certa

inty

4 4.015 3.993 242 5.45 3.38 0.315 0.020 -0.5% 1.3% 0.0% 1.8% 2.3%

4.5 4.494 4.443 266 5.47 3.38 0.305 0.019 -1.1% 1.2% 0.0% 1.8% 2.5%

5 5.008 4.976 365 6.07 3.41 0.360 0.019 -0.6% 1.1% 0.0% 1.8% 2.2%

5.5 5.512 5.532 399 7.72 4.10 0.372 0.019 0.3% 1.0% 0.0% 1.8% 2.1%

6 6.006 6.027 439 8.13 4.98 0.362 0.017 0.4% 1.0% 0.0% 1.8% 2.1%

6.5 6.492 6.525 512 8.06 5.45 0.346 0.015 0.5% 0.9% 0.0% 1.8% 2.1%

7 6.982 7.034 478 8.81 5.75 0.404 0.018 0.8% 0.9% 0.0% 1.8% 2.2%

7.5 7.493 7.524 399 9.62 6.54 0.386 0.019 0.4% 0.9% 0.0% 1.8% 2.0%

8 7.992 8.056 340 9.63 7.07 0.438 0.024 0.8% 0.9% 0.0% 1.8% 2.2%

8.5 8.480 8.502 286 10.06 7.35 0.453 0.027 0.3% 0.8% 0.0% 1.8% 2.0%

9 8.972 9.056 275 10.62 7.85 0.475 0.029 0.9% 0.8% 0.0% 1.8% 2.2%

9.5 9.491 9.580 218 10.87 8.34 0.506 0.034 0.9% 0.8% 0.0% 1.8% 2.2%

10 10.006 10.189 212 11.86 8.88 0.551 0.038 1.8% 0.8% 0.0% 1.8% 2.7%

10.5 10.489 10.647 178 12.27 8.50 0.563 0.042 1.5% 0.8% 0.0% 1.8% 2.5%

11 10.999 11.158 144 13.17 9.77 0.599 0.050 1.4% 0.8% 0.0% 1.8% 2.5%

11.5 11.475 11.633 96 13.21 10.27 0.633 0.065 1.4% 0.7% 0.0% 1.8% 2.4%

12 11.985 12.067 90 13.63 10.66 0.571 0.060 0.7% 0.7% 0.0% 1.8% 2.1%

12.5 12.484 12.544 67 14.25 10.98 0.678 0.083 0.5% 0.7% 0.0% 1.8% 2.1%

13 13.008 12.974 68 14.89 12.13 0.596 0.072 -0.3% 0.7% 0.0% 1.8% 2.0%

13.5 13.534 13.602 57 15.90 11.87 0.781 0.104 0.5% 0.7% 0.0% 1.8% 2.1%

14 13.979 14.067 54 15.89 12.78 0.716 0.097 0.6% 0.7% 0.0% 1.8% 2.1%

14.5 14.466 14.318 34 16.29 13.19 0.595 0.102 -1.0% 0.7% 0.0% 1.8% 2.3%

15 14.938 14.849 24 16.04 13.74 0.552 0.113 -0.6% 0.7% 0.0% 1.8% 2.1%

15.5 15.524 15.253 16 16.72 14.06 0.738 0.185 -1.7% 0.7% 0.0% 1.8% 2.8%

16 15.980 15.620 6 17.78 13.79 1.425 0.582 -2.3% 0.7% 0.0% 1.8% 4.7%



Bin

Vcu

p

VR

SD

Nu

mb

er o

f

data

sets

VR

SD m

ax

VR

SD m

in

VR

SD-s

td

VR

SD-s

td/√n

Mean

devia

tio

n

Vcu

p

un

certa

inty

Mou

nti

ng

un

certa

inty

Flo

w

un

certa

inty

VR

SD

un

certa

inty

4 4.025 3.955 351 5.26 3.37 0.303 0.016 -1.7% 1.3% 0.0% 3.6% 4.2%

4.5 4.495 4.442 501 7.25 3.42 0.384 0.017 -1.2% 1.2% 0.0% 3.6% 4.0%

5 4.999 4.961 514 6.84 3.83 0.406 0.018 -0.8% 1.1% 0.0% 3.6% 3.8%

5.5 5.500 5.500 511 7.96 4.07 0.402 0.018 0.0% 1.1% 0.0% 3.6% 3.7%

6 5.997 6.003 430 8.20 4.74 0.402 0.019 0.1% 1.0% 0.0% 3.6% 3.7%

6.5 6.498 6.546 373 8.06 5.20 0.463 0.024 0.7% 1.0% 0.0% 3.6% 3.8%

7 6.985 7.071 376 8.99 4.88 0.489 0.025 1.2% 0.9% 0.0% 3.6% 3.9%

7.5 7.491 7.604 280 9.11 6.49 0.471 0.028 1.5% 0.9% 0.0% 3.6% 4.0%

8 7.995 8.108 251 10.01 6.59 0.537 0.034 1.4% 0.9% 0.0% 3.6% 4.0%

8.5 8.500 8.657 223 10.61 6.60 0.621 0.042 1.9% 0.8% 0.0% 3.6% 4.1%

9 8.991 9.145 185 10.95 7.54 0.595 0.044 1.7% 0.8% 0.0% 3.6% 4.1%

9.5 9.518 9.689 176 11.60 8.08 0.650 0.049 1.8% 0.8% 0.0% 3.6% 4.1%

10 9.972 10.113 143 12.19 8.69 0.596 0.050 1.4% 0.8% 0.0% 3.6% 3.9%

10.5 10.483 10.721 117 13.00 8.97 0.759 0.070 2.3% 0.8% 0.0% 3.6% 4.3%

11 10.989 11.100 64 14.13 9.35 0.785 0.098 1.0% 0.8% 0.0% 3.6% 3.9%

11.5 11.504 11.736 69 13.60 9.61 0.829 0.100 2.0% 0.8% 0.0% 3.6% 4.3%

12 12.012 12.272 72 14.34 10.74 0.824 0.097 2.2% 0.7% 0.0% 3.6% 4.3%

12.5 12.484 12.678 55 14.69 10.73 0.781 0.105 1.6% 0.7% 0.0% 3.6% 4.0%

13 12.997 12.835 31 14.84 11.76 0.611 0.110 -1.2% 0.7% 0.0% 3.6% 3.9%

13.5 13.541 13.408 23 14.26 11.91 0.541 0.113 -1.0% 0.7% 0.0% 3.6% 3.9%

14 13.992 13.743 25 14.79 12.86 0.557 0.111 -1.8% 0.7% 0.0% 3.6% 4.1%

14.5 14.510 14.432 16 16.29 13.61 0.605 0.151 -0.5% 0.7% 0.0% 3.6% 3.8%

15 14.913 14.870 11 15.83 14.03 0.587 0.177 -0.3% 0.7% 0.0% 3.6% 3.8%

15.5 15.500 15.041 13 15.99 14.25 0.620 0.172 -3.0% 0.7% 0.0% 3.6% 4.8%

16 16.052 15.339 12 17.46 14.23 0.957 0.276 -4.4% 0.7% 0.0% 3.6% 6.0%

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SoDAR Verification Test - Vaisala · 2018. 7. 20. · The verification analysis is based on the IEC...

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