Topic: Anenometer installation height

[src]

I know the standard height is 10m (33ft) but that seems rather high!

I am able to install my anenometer well away from buildings or other obstructions - I'm going to mount the pole on a gatepost between two fields. There is a dry-stone field-wall only about a meter (3ft) high, and one medium tree about 50m (160ft) away.

With what I have available I'll fairly easily be able to install my anenometer at a height of over 4m (approx 13ft-14ft) or perhaps 5m (16ft). That is high enough, isn't it? What % difference in wind speed might I see if I went higher?

Thanks

[Vasco]

What % difference in wind speed might I see if I went higher?

See attached, from UK Met Office.

[src]

Hmm, so 4-5m is not really very high then...

[Vasco]

Siting of weather stations, like life itself, is full of compromises. . .

Just do the best you can 

[mcrossley]

See attached, from UK Met Office.

And don't forget that table only applies to heights in an unobstructed open field. If there are obstructions then the factor will likely be significantly higher.

[scudwatcher]

Greetings from the CSRA!  I have a Davis Vantage Pro 2 Plus w/ 24 Hour FARS mounted to a 21 LF in length, chain-link fence 1.25 inches diameter top rail.  The Davis Instruments anemometer is installed at the top portion at a height of 19 Feet AGL.  The Davis Instruments ISS is mounted at a height of 5 Feet AGL.  The post was installed in the ground for at least 2 Feet below AGL.  Due to my REPRESENTATIVE station location, there is only minimal observed wind speed / direction difference from the previous anemometer height of 8 Feet AGL versus 19 Feet AGL.  My representative station location is in a residential subdivision with numerous trees.  My Local National Weather Service Forecast Office, Observations Program Leader approved my station location for performing Cooperative Surface Weather Observations.  Just install your anemometer at your station in the best location possible for your wind speed and direction data to be REPRESENTATIVE to your specific location.....Cheers.

[johnd]

...Just install your anemometer at your station in the best location possible for your wind speed and direction data to be REPRESENTATIVE to your specific location.....Cheers.

That is all very well, but rather ignores the fact that there is an official standard height for measuring wind speed which, as others have said, is 10m. And in a perfect world that is certainly the height to aim for.

But we all have to live with compromises and so the usual advice is simply to get the anemometer as high as is practicable for your given location and, perhaps more importantly, as distant from surrounding obstructions as possible. Only you will know about what is feasible for your own location but there is no doubt that the higher you can get the anemometer (safely and robustly, ie no long untethered poles that sway or vibrate strongly in the wind). The chart that Vasco provided gives you correction factors for different heights.

[box]

Mines at 6 metres AGL

I think the important thing is horizontal clearance from trees and buildings

My site meets that requirement, but 6 metres is the length of poles and stays that I could afford/justify

If you get up to 10 metres you might start running into issues with planning or neighbours!

[src]

Thanks for the various comments.

My proposed site is 50m from a single tree which is only about 5m tall. Other than the low stone wall (<1m) there are no buildings nor other trees within about 120m.

At this site I won't be able to fit guy ropes - the cattle in the field would trip over them and either pull the guys out of the ground or pull the mast down!

I have a 12ft long pole which is 42mm external diameter (1 2/3 inch). It is rather like a scaffolding pole but I think it is either an old handrail or piece of old iron heating pipe. It is quite heavy but also very rigid and will not sway in the wind.

I propose to secure it to the gatepost using two of these:

https://cpc.farnell.com/blake-uk/wb20-g/6-x6-standoff-wall-brkt-galvanised/dp/AP00962

I may let the lower end of the pipe rest on a rock on the ground to take some of the weight.

To the top of this I’ll clamp a 6ft x 1inch pipe on top of which I can secure my Ecowitt WS90 (which is designed to fit on top of a 1inch mast).

With an overlap of 1 foot where the two poles are strapped together I’ll end up with a mast reaching 17ft (5m) which I think is enough. I’ll set correction to 10%.

With only 5ft of thinner pole being unsupported hopefully there will be little wind-induced sway. If there is significant sway I could lower the top pole and restrap the two poles with a much larger overlap and a shorter top section.

I’ll let you know…

[box]

I think you may be surprised by the amount of movement

I tried mine unstayed for a month or so. It only had a WS68 on it, not a full station but it certainly moved around!

It's aluminium poles though so you may have more success with yours as they sound more substantial

What are you packing the gap with or does the smaller pipe slide inside the larger one with no gap?

I'd watch that gatepost too, there is a big turning moment from a tall mast, a lot more than from a gate..

Good luck!!

[cpufrost]

Trees at my site are a big challenge!
I have a 60' Rohn 25G tower as pictured.  Tempest at 75' AGL.



It is amazing how much different the gust values are over the stations below.

Since that pic was taken, the TEMPEST (on SIXTH unit now!) has been moved to a tripod mast and the wind gap is right at 33' AGL.

TEMPEST stations are clearly not suitable for tower/professional mounting.  False rain aside, the sensor packs experience failures and retrieval is no fun!

[TheBushPilot]

Wow that tower is awesome. What kind of wind loading can that thing handle?

[cpufrost]

It's bracketed at 18' and without guys I wouldn't put more than 1-2 sq feet at that height.  With guys at 30' and 57' easily 20 sq. ft at 90mph.

The PTZ up there does reveal sway in strong winds!

https://www.youtube.com/watch?v=AvZO-i7uiWA

I have it at 42' currently with the WS2000 in my sig on a 1.5" SCH40 galvanized mast currently and it's pretty solid.

I do plan to go back to 62' with proper guying to keep things solid.

One thing's for sure; no more TEMPEST units going up there!

[box]

Trees at my site are a big challenge!
I have a 60' Rohn 25G tower as pictured.  Tempest at 75' AGL.



It is amazing how much different the gust values are over the stations below.

Since that pic was taken, the TEMPEST (on SIXTH unit now!) has been moved to a tripod mast and the wind gap is right at 33' AGL.

TEMPEST stations are clearly not suitable for tower/professional mounting.  False rain aside, the sensor packs experience failures and retrieval is no fun!

wow! Are you running a space programme too?

[cpufrost]

Not space but I'd like to lease some land here for the telecoms.  They pay nicely!

[ocala]

Curious, did you climb that tower to install those?

[ocala]

My anny is at 30 ft but I had a death grip on the tower when installing it. Definitely not a fan of going up there again. Of course the cam was much easier.
 [ You are not allowed to view attachments ]

[cpufrost]

Curious, did you climb that tower to install those?

In my younger days I used to install everything by climbing!  At the top I would be strapped in and just hoist antennas carefully balanced up and lift the booms over the mast and tighten up the u-bolts.

Today I winch it.  The base hinges over thankfully!

Side mounts are easy.  Just something about being at the very top of the tower gives that uneasy feeling.  Of course I'd never recommend anyone climbing without proper safety gear and training!  It's hard being a one handed installer!   And worse being a fall guy!

Here's the same tower in 2015, my nephew who was 15 at the time wanted to help with pulling down some antennas after a lightning strike in the summer of 2014.

[CW2274]

My anny is at 30 ft but I had a death grip on the tower when installing it. Definitely not a fan of going up there again.

    Ain't enough money.....

https://i0.wp.com/laughingsquid.com/wp-content/uploads/2015/01/a-tower-climber-makes-his-way-to.jpg?w%5Cu003d600

[davidmc36]

Nor this:
https://youtu.be/INbKYq0G9nU
I went up my 32 foot tower to install multiband antenna when we first moved in. Never again.

[Lord Volvo]

Compromises, indeed.  Living in an older suburb has many mature trees nearby but I still manage to catch enough wind with my old Heathkits. [ You are not allowed to view attachments ]

[src]

Thanks for the various comments.

My proposed site is 50m from a single tree which is only about 5m tall. Other than the low stone wall (<1m) there are no buildings nor other trees within about 120m.

At this site I won't be able to fit guy ropes - the cattle in the field would trip over them and either pull the guys out of the ground or pull the mast down!

I have a 12ft long pole which is 42mm external diameter (1 2/3 inch). It is rather like a scaffolding pole but I think it is either an old handrail or piece of old iron heating pipe. It is quite heavy but also very rigid and will not sway in the wind.

I propose to secure it to the gatepost using two of these:

https://cpc.farnell.com/blake-uk/wb20-g/6-x6-standoff-wall-brkt-galvanised/dp/AP00962

I may let the lower end of the pipe rest on a rock on the ground to take some of the weight.

To the top of this I’ll clamp a 6ft x 1inch pipe on top of which I can secure my Ecowitt WS90 (which is designed to fit on top of a 1inch mast).

With an overlap of 1 foot where the two poles are strapped together I’ll end up with a mast reaching 17ft (5m) which I think is enough. I’ll set correction to 10%.

With only 5ft of thinner pole being unsupported hopefully there will be little wind-induced sway. If there is significant sway I could lower the top pole and restrap the two poles with a much larger overlap and a shorter top section.

I’ll let you know…

I said I'd report back but I never did. I installed as described above. It has kept steady with only slight movement in 50mph gusts.

Photo attached. Am I far enough from trees, buildings etc?