Menu Sign In Contact FAQ
Banner
Welcome to our forums

Weather Station - cloud base

I had a student make a ceilometer as a project last year. It was based on an Arduino with an IR sensor and cross compared the cloud temperature with the latest radiosonde data from Valencia to read out an altitude..it compared quite favourably with the EIDW metars for the most part, when tested about 3 km away.
Is there that much difference between the EIME data and EIKH on a given day?

EIMH, Ireland

That’s an interesting approach… The sonde data is 0000Z and 1200Z. I would be surprised if it is ok for flying say 1100Z, in typical N European wx.

A laser based meter should not be hard to make. One would use an IR laser to avoid detection and compliants, and use a standard off the shelf low power one. Then you would need some optics on the receiver; a bare photodiode pointing at the sky is unlikely to get a useful signal back. Possibly some form of synchronous demodulation might be needed to extract the signal from noise; pehaps transmit a burst of 100kHz pulses and then look for the 100kHz coming back, with a fairly narrow filter. Hmmm 100m/320ft = 3us only so maybe just look for the leading edge, within a time window. @AF may know better ways.

The CL61 LIDAR clearly uses some optics, even though they say “single lens”. And just one convex lens ought to be enough, with the photodiode at the focal point.

An interesting project

Administrator
Shoreham EGKA, United Kingdom

zuutroy wrote:

Is there that much difference between the EIME data and EIKH on a given day?

If they are really close on different elevations, the delta of airfield elevations? if they are far away on same elevation, you can use ratio of Temp-Dew spread in both locations to adjust known cloudbase from one into the other?

Last Edited by Ibra at 29 Mar 08:07
Paris/Essex, France/UK, United Kingdom

I’d agree a webcam is a good solution – especially if you could swivel it remotely. The key is for it to be showing a landscape you’re familiar with and used to judging with respect to flying weather.

I look at this before driving down to EGLM, and although the image isn’t much to look at I’ve spent enough time standing on that grass looking at the sky to be able to form a reasonable judgement.

EGLM & EGTN

CamAero has Raspberry Pi webcams with superimposed heading, local heights and weather, and the operating system is for free on an SD card (don’t know if they’d do it outside France). Looking at google streetview for EIKH there aren’t really any hills to compare cloud base, except for maybe to the northeast.

EGHO-LFQF-KCLW, United Kingdom

Thanks for all the advice.

gallois wrote:

We installed an off the shelf cheap weather station and wind sensor at our airfield, but no-one really uses it.

That’s an interesting comment. The more I think about it, the less I think the weather station is important. Rainfall isn’t really relevant and a radar picture will tell more about that. Windspeed and direction is hard to get right as it involves getting the measuring equipment up high to avoid local obstructions. And in any case, I very rarely cancel a flight due to wind. Ireland is a windy country. We get used to cross winds very quickly
It’s the cloud base that is more interesting to me. So I think you are right. The weather station isn’t important and the webcam is.

Alpha_Floor wrote:

I think this works better in still wind conditions and with larger temperature spreads, but the problem is that it’s not very useful in marginal cases where the cloud base could potentially be an issue. When the temperature spread is a few degrees you could have a base of 500, 1000 or 2000, too much of a margin of error to make a go/nogo decision. Of course when the spread is 10 degrees, you don’t really care if the bases are at 3000, 5000 or 7000…

That’s it exactly. If the cloud base is more than 2000ft, I no longer care what it is. It’s flyable. Our mountains aren’t very high or expansive. 2000ft is good enough for most flights and if something is blocking it higher than 2000ft, I can go around it.
Below 1000ft I won’t fly. So it’s the in between bit that I care about. 2000ft at home (or nearest METAR) and 900ft at the airfield is what I need to know about.
So rules of thumb aren’t all that useful.

Ibra wrote:

At my gliding club in Dunstable they had two webcams, one against the hill and one toward the horizon

That’s what I have in mind now. It seems the best solution.

zuutroy wrote:

Is there that much difference between the EIME data and EIKH on a given day?

I don’t honestly know. There have been a few times when the weather at home (half way between EIWT and EIME) was poor but improving and the forecast on EasyVFR showed it better towards EIKH (I mean the improvement was moving from SW to NE). I drove there and sure enough it was better. It could just have been the improving weather or better at that location. EIWT and EIME are still subject to the coastal effect that EIKH wouldn’t be, and EIKH is typically on the upwind side of the mountains. I’ve also seen cloud sitting on the upwind slope of those mountains stretching to maybe 1-2km from EIKH. Maybe that’s as close as it ever get, or maybe sometimes it’s an issue. But I won’t know for sure until this lockdown is over and I get to do some more flying

Graham wrote:

I look at this before driving down to EGLM, and although the image isn’t much to look at I’ve spent enough time standing on that grass looking at the sky to be able to form a reasonable judgement.

Yes, I think that’s really where I’d like to get to.

I just want to avoid a 90 minute round trip which is wasted!

Building a ceiliometer is well beyond may capabilities. But a remote webcam should be doable. I think that’s the best solution. I’ve ordered the bits. I’ll try setting it up at home and if it works ok, I’ll talk to the airfield owner and see if he would be ok with it.

If nothing else, it’s an interesting project during lockdown

EIWT Weston, Ireland

dublinpilot wrote:

It’s the cloud base that is more interesting to me.

And the visibility?
I heard from someone that people at a remote place installed a webcam and then a few solar-powered garden lights at a distance (with some interval) – that way you can get the visibility by counting the lights at night/early morning, you don’t need that during the day, you just check the distance.

EGTR

Just in case there is any doubt, a webcam is the way to go.
Flying VFR, if ever I am in doubt looking at METARs/TAFs which can happen regularly in Late Autumn/Winter/Early Spring due to localized mist/haze then googling for webcams is a great way to see whats happening weather wise on and off the airfield.

Regards, SD..

Dublinpilot, Kilrush re-installed a webcam a couple of months ago, aimed northwest and viewed via a mobile app.
The field of view includes windsock, the electricity pylons at 2 nm (for local visibility) and hills at 7 nm (re whether the cloudbase is low, plus visibility).

If you email me I’ll dig out the app instructions.

The EIME Metar is mainly useful just for QNH; if weather might be a factor limiting a day’s flying, conditions at EIKH are sufficiently different from those at EIME that one could not infer with any certainty the former from the latter. Due to Covid I have not yet had an opportunity to try getting the EIKH webcam while inbound from abroad, this could be very useful in getting oneself positioned for a legal approach into this VFR-only airfield.

Bluebeard
EIKH, Ireland

Thanks Bluebeard.

Email sent.

EIWT Weston, Ireland
Sign in to add your message

Back to Top