A VP2 installed in the normal way, including compromises on siting, is probably as good as you need to go if it’s just for public information purposes. If you tell people it’s 82degF when it’s between 77 and 87 degF most people won’t argue (unless they have an accurate screened thermometer and are hoinding it right next to your temperature sensor). Same for wind speed…people think in terms of how windy it is at 5-6 feet off the ground, not whether it’s exactly 27.9mph 30ft up in the air. Even the tallest man in the world is still more than 20ft short of having his head in the winds at 30ft! You probably pass numerous big temperature signs as you drive around your area…I’d like to bet their sensors aren’t located in anything like the ideal positions, but people still look at them and believe that they’re telling the right temperature. Did you ever consider how accurate the temperature on those big signs was until you tried siting your own station? Probably not, but you probably have taken the temperatures as being reality.
I’m not suggesting you make numbers up…just that you may be striving for a level of perfection that your audience doesn’t need (or even know it needs). For example, I know that some people use the data from my station, despite it’s compromised siting and the people who have used it have never asked how well it’s sited!
You don’t have to mount the bucket and the anemometer together. Although I admit you do see pictures with it that way, the typical single pole install will put the anemometer a lot higher on the pole than the rain gauge, and that should be satisfactory for most purposes. In the standard station package the anemometer comes with a 40’ cable and the necessary U bolt for it to be mounted separately.
I opted for the “up, up and away” approach to mounting my Davis VP2. My thought was; I’d rather lose some temperature accuracy (although I don’t see how raising the temp. sensor above 5’ does that) to ensure a good wind and rain reading.
I ended up mounting the ISS about 25 feet in the air (on an old bird house pole):
Click photo to enlarge:
The temp. readings don’t seem to suffer (these are unadjusted CWOP readings):
It seems if you are going to use a single pole, you have no choice but to put the whole mess at the top. If you try to mount the rainbucket further down on the same pole, i.e. 2’ above the ground, the pole itself will block the rain and perhaps cause some sort of swirling action? That is why I though you would need the 33’ pole for the anemometer and another pole some distance away with the rest of the stuff on it or perhaps three poles. The short one for the bucket, the medium one for the temp, and the tall one for the anemometer. If you also had a solar or UV sensor you wouldn’t want a pole shadow to fall across it so it would probably be on your tallest pole too. It looks like in your picture that you have bushes around the pole taller than the pole? That is my problem…the trees near my current pole aren’t taller but will be in a matter of a few years and there are trees further away that are 60-80’ tall so I just need to stay a long ways from them. I saw a formula somewhere for how far you needed to be away from taller things to reduce or eliminate any interference?
I could be wrong, but it seems that air temp is about the only thing that wouldn’t be as sensitive to location as other readings?
I had an errand this afternoon so I though I would drive by the two stations nearest to me to see what their equipment was and how they had it sited.
The first stop was the area airport. The CWOP map shows their WS in the middle of the runway which I knew wasn’t likely. Turned out there weather station was several blocks away and didn’t even appear to be on the airport property. Was in a cornfield near a cemetary. I couldn’t get there from the airport so I thought I would pay it a visit some other day.
The other site I stopped by was the closest personal station, a Davis. They guy had it mounted on his chimney. It was one of those fake chimneys that doesn’t even extend above the apex. His station was on a short pole and his non-aspiriated temp sensor wasn’t even a foot above the roof, if even that. So his sensor was non-aspirated and had to be consumed by heat from the brown shingled roof. The only saving grace was it was a 2-story house so there was probably some wind. I am guessing he was either relinquishing to the better half or wanted his station to be “low profile”. Also, not more than 20’ or so away was a tree taller than the roof of his house. On my next jaunt I will go by the other airport just south of me and another person station just north of me. The one north of me has problems. The CWOP map shows his registered location and his APRS location to be .9 mile apart? I don’t know how APRS knows such things?
Anyway, his barometer is WAY off…he not only gets two thumbs down in MADIS, but his site stands out like a sore thumb compared to other stations in the area.
Anchorage, my current anemometer is mounted on a old Martin house pole that was in the yard. The Martin house got ripped off when what I think was a tornado came through, or nearly through.
I think you are also sacrificing your rain reading as supposedly there is more wind the higher you go and the higher wind keeps all of the rain from falling into the bucket?
I saw those quite elaborate fence looking things people have mounted around their rain buckets. In fact, I think they were actually a commercially made product to block “all” wind from reaching the bucket.
I saw those quite elaborate fence looking things people have mounted around their rain buckets. In fact, I think they were actually a commercially made product to block "all" wind from reaching the bucket.
That is one type I saw, I also saw another very similar type. In the one case they actually had multiple rings of things similar to that. The link gave me an idea for mine using plastic snow fence that comes in 4’ widths which would be folded over in half making it 2’ high so the top would be even with the top of the rain bucket, if in fact I take the rain bucket off of the ISS.
got it…I wasn’t comparing the Alter version to the snow fence version, I was comparing old style stick snow fence to the more modern plastic version.
I think surrounding the rain bucket with the modern snow fence material would accomplish part of the task that the Alter does.
I don’t get what additional value having them able to swing provides but they must have thought there was some merit to that design, or at least they want you to think there is I haven’t seen a study on the various surrounds. I noticed the sample AWI system now being used at airports doesn’t have any kind of a surround around their bucket.
I swung by the Rainwise site to check out their rain buckets and found that they show the Alter design as an option to their setups.
According to Accuweather “The advantage of this [Alter] shield is that the slats do not easily accumulate snow, permitting its use on unattended gauges”.
Seems to me it wouldn’t matter if they collected snow on them if the whole works is sitting in several feet of snow
I am contemplating a method to mount the rain bucket and temp sensor on a moveable arm such that I can go out and raise it from time to time as the snow accumulates under the sensors.
My current plan is to put in a new, taller mast instead of using the martin house pole my anemometer is on now. Then I will add a PVC pipe a larger diameter that can slide up and down on the mast pipe and I would use a hose clamp under it I can lossen and move as necessary. Off of that vertical PVC pipe will be two opposing horizontal arms, but not at the same height. On arm would be lower and would have the rain bucket on it and a higher arm would have the temp sensor and ISS on it. The cable from the anemometer would come down from above and would have a loop in it so it could be moved up and down as necessary.
Seems easy enough plan and gives me the flexibilty to raise and lower the whole works as needed. The other added value is I can temporarily raise the arms to mow under them
Seems like an inelegant but workable plan…has anyone tried something like this? At least those where it snows?
We all know the Davis ISS was designed for the simplest installation possible, disregarding optimal siting options. Ideally all components would be independent and could be scattered around ideally like my Honeywell. However the Honeywell’s wireless distances aren’ adequate for my needs. I needed to figure out a way to get my new site sited as well as possible without buying a lot of extra stuff. I came up with a design that I think creates a great site score and solves other problems at the same time like mowing under the bucket and dealing with snow depth.
Here is my current concept, please be as critical as possible as it is all just theoretical at this point as my Davis hasn’t arrived.
Oh ya, I have already expanded the concept to change the bracket under the rain bucket to attach an Alter style wind ring which can also raise and lower with the bucket.
Looks good except that’s probably not a great location for the solar sensor. What I have done is to extend the solar sensor cable and mount it at the top of the mast with the anemometer (need another home made bracket).
I would highly suggest that you try a much simpler configuration first. After that, if you are not satisfied with the result, you could experiment etc…
I doubt you will get much of a difference in numbers if you simply place your Anemometer up on the Roof and mount your ISS as a whole on a post at 5-6ft. No Alter style wind break, no PVC pipes (most likely will bend and sway anyway).
You are going to a lot of trouble to be perfect with what I think will end up being negligible different results from a more common simpler setup. This is especially true when you factor in the accuracy of the instruments and issues in your area that will effect your sitting location (Unless you plan on cutting down some tree’s too).
I think you’ll find the rain gauge bracket will be unstable and you will probably suffer from false rain readings due to the gauge being buffeted by strong winds. I also think you’re unlikely to be able to raise/lower the entire unit carefully enough to avoid false rain readings when you want to mow under the structure.
I think he could mow under it… use one of those string trimmers, or since he is going with the concept of putting in a mast, could modify the surface under it, either kill off the grass ( the misses will like that one, you can bet… talking from experience and a lot of grass seed later), put in a drain of pebbles or pea gravel under it in a depression with something to allow the water run off.
I would wonder one thing… will the front of the solar panel get the sunlight , be able to send the signal up to his console, that is the antenna signal spread and then what happens in snow or any environmental situation.
Finally, will it meet NWS / NOAA/? standards for rain collections as being correct.
But it could be done. and this advice comes from a man sitting trying to modify his website theme, listing to ABBA on his ipod and realizing it is best to hear that when the family is gone, they might think I have become fruity…
I am curious why you thought that about the solar sensor. The sensor would be south of the pole and should never have a shadow? is the sun different at 2’ vs. 33’?
I don’t want to have to add a wireless unit to the anemometer. The solution I propose only requires a cable from the ISS to the temp sensor, nothing else as the other cable from the anemometer to ISS is provided and is long enough. I don’t know of any other way to put one thing on the house and the other 75 ft away in the yard other than a long cable and trenching it into the ground?
I don’t consider it a lot of trouble and your suggestion still leaves the issue of mowing around it? PVC pipe is pretty sturdy if a big enough gauge is used and there isn’t much sway 2’ up the mast???
I didn’t say where I would mount this so trees might not be a factor. Actually, trees are no more a factor where my current mast is than on the house…actually, there are taller trees closer to the house (and taller than the house) than where my current mast is. I am still considering mounting this out in the field away from everything.
The PVC pipe is cheap and stronger than I think you think Go to the hardware store and grab some 3 or 4" PVC. I bet you couldn’t bend it. I can’t and the time to do what I am proposing is probably less than the drawing took to make If I thought it would take a lot of time, I wouldn’t be doing it.
I was going to initially install it on my current mast and see if the plan works, then install it on a stronger, taller mast when I see if the concept works.
So you have a clear shot to the horizon from NE to NW from 2’ AGL? No trees, no houses, no outhouses, no passing Bambis, no leaping walleye, just a flat plain? Nothing that could cast a shadow on the sensor at any time of day or year?
