windsensor height correction button

[kfeelders]

.
Suggested is a way (button) to adjust (correct / offset) the windstrength / windspeed /windgust values so they
can be set according to the height of the windsensor.

Normally windsensors suppose to be installed at 10m heigth, but often they are higher (or lower) where the windspeed is
higher (or lower) as compared to the speeds on this 10m.

There exist a table which shows the offset of windspeed compared to the 10m value, see below.
h is height in meters of the sensor, W is the windspeed in m/s on that height.

It means that a sensor placed on 20m height shows 33% or so more speed, so this one should be able to be corrected /
offset -33%

See this thread and post for the initial discovered problem:
viewtopic.php?f=74&t=27689&start=20#p216748

Regards Kees

[Toulon7559]

Kees,

To better understand the background of your suggestion:
1) what is the source of this correction-table for windspeed=f(height)?
2) how do you apply the measured wind-data?

Ad to 2)
Not up front in Domoticz, but if (in the meteo-system) the data is received&processed in a console or in a software program, quite often a possibility is available to insert adjustable offsets for calibration, either as a constant bias, or as a relative factor, or as a combination.

[kfeelders]

.
Toulon7559,

thanks for the reply.

The source for the little table above comes from this Dutch website:

http://www.hhofstede.nl/opgaven/examens ... 22006I.htm

but searching on Google, you will find many references like this Danish website:

http://drømstørre.dk/wp-content/wind/miller/windpower%20web/en/tour/wres/calculat.htm

So the windspeed not only varies by height, but some other factors too, but a rough relation with heigth
is the most strongest.

Probably there are weather sensor stations which can adjust/offset the windspeed due to height or whatever,
but probably many others not.

So therefor it seemed easy enough to implement a kind of offset in the "settings" for Domoticz for this.

Just a suggestion though.


Regards Kees

[Toulon7559]

Kees,

The reason for my questions:
1) "a measurement serves a specific purpose".
For meteo certain rules apply for optimal setups and processing as defined by KNMI and by comparable organisations.
See https://www.knmi.nl/kennis-en-datacentr ... ndmetingen and http://projects.knmi.nl/hawa/pdf/Handboek_H05.pdf
For e.g. wind-energy different rules apply as described e.g. in http://drømstørre.dk/wp-content/wind/miller/windpower%20web/en/tour/wres/wndsprac.htm
2) In relation to 1) it makes a difference whether you apply the wind-info for local, 'simple' personal use, or whether you externally distribute the info to other users for a specific purpose. That difference does not preclude that you want to aim for high quality, but the difference usually also induces a certain 'relativity' due to 'practical aspects'.
Example: for a Personal Weather Station in a Netherlands' rural or urban area, how do you correctly determine the m and r as required for the 'better' formule in the quoted exam?

[kfeelders]

.
T,

i agree, i use this wind-info for local, `simple` personal use, but i noticed that the data coming from this
WH24 station at 20m height is about 33% off (plus) compared to actual wind speeds from KNMI etc. (so in agreement
with the mentioned table).

I can of course apply this -33% in my mind when looking at the wind data, but a more elegant way would be the posibility to
give this -33% offset in domoticz.

Kees

[Toulon7559]

Kees,

Understood.

In my own PWS-configuration the PWS-Console(s) provide the 'unspoiled' data-picture ~ 'raw' source data.
Domoticz' Widgets provide facilities to insert basic offsets as 1st, limited correction on received data for temperature, air pressure and rain.

In my PWS-configuration then as 2nd, additional correction several scripts operating on Domoticz' data provide the extra required calibration-offsets for wind, air pressure, temperature and rain to make the outputs of the scripts show the 'true values' after calibration.

These scripts feed virtual devices and graphics, and make uploads for various applications.
For uploads Calibration is an aspect requiring attention:
different organisations have different requirements which data and how must be calibrated.
The 2nd correction in the scripts provides the flexibility to tune the various outputs to virtual devices, graphics and uploads, superior to just 1 general correction to an input.

MVG, Anton

[Toulon7559]

@kfeelders, and other forum-members ....

Practically looking at the anemo-devices in my PWS-configuration, I have some reservations related to the height correction function.
Not to the request and to background as such, but to the practical value.

In my configuration I have 3 anemometers installed on a common mast, spaced a approx. 1 m mutual distance above each other:
see this picture
The top device is TFA_Nexus, the middle one is LaCrosse WS7000, and at the bottom is an 'unidentified' device at some time purchased from Conrad.
If those devices have been well designed & produced, from the related PWSes you could expect an output which is more or less in the same range.

Because of some 'strange' observations for the 2 top devices (and the bottom one being uncalibrated), I have tried to calibrate & align those 3 devices:
simply meaning that I have measured and compared between each other and relative to other anemo-devices in the neighbourhood.
The result was a real surprise:
see http://www.vannwnhzn.nl/Experimenten.html#07 [as subpart of my website at http://www.vannwnhzn.nl/Sitemap.html ]
Considering the observed effects, a height setting might be correct, but first a basic calibration & alignment is required.
In that perspective it already would be a big help if Domoticz would have a basic first relative correction for the values for wind-speed and for wind-gusts, as already available for rain, temperature and pressure.