Author Topic: Determining Heights for PWSs  (Read 1926 times)

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Offline kbellis

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Re: Determining Heights for PWSs
« Reply #25 on: January 06, 2019, 10:40:24 AM »
Back on the topic for a tic

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1) WU asks for both the height of the instrument, anemometer from the looks of the little illustration, and also asks for an elevation. Implicitly (?) this elevation would be at grade of the sensor array. Datum doesn't seem to matter. Oh, and before I forget it again (CRS!), the difference between NAVD88 and NGVD29 varies from place to place. For us here in coastal Hancock County, the difference between these two terrestrial datum is less than 0.7', while elsewhere in the U.S., you'll find differences over three feet. Here's a couple of examples, but I encourage those interested in learning of the difference for their own locality to use VDatum - after the hostage situation has ended. For example:

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2) PWSWeather asks for an elevation and almost explicitly (ref. TopoZone link) is asking for an elevation at grade of the sensor array. No specific terrestrial datum is specified.


3) Weathercloud also appears to be requesting for a ground elevation for the sensor array, but they're using the word "Altitude" for reasons unclear. They also ask for the height of the PWS. No specific terrestrial datum is specified.


4) Ambient Weather isn't particularly interested in the elevation of grade for the sensor array or the height of anything. I asked Ambient for clarity and got this reply:

VKB: "Does AmbientWeather.net use elevation information? I can't find anywhere in the Dashboard that reflects height of instrument, grade elevation at instrument, or height of barometer.
Thanks
Kelly
"

AW: "Nope. The calibration is done on the console with an offset.

Ed
"


5) AWEKAS asks for elevation above sea level with its tool tip saying "Indicates the altitude of the station or measuring point." No specific terrestrial datum is specified.


6) CWOP appears to also want the elevation at grade of the sensor array; however, the referencing links in the CWOP FAQs that I chased after are old and returned 404 errors. No specific terrestrial datum is specified from what I saw.

From everything that members have posted above, and elsewhere on this forum, and from what might get pieced together from looking at the above cited online services, elevations, irrespective of a specific terrestrial datum, related to the PWS are primarily located at grade of the outdoor sensor array.

Confession: In addition to an elevation at grade being sought, my inner nerd child was imagining it worth considering the heights of other things, like each of the sensors individually, e.g., rain gauge, thermometer, barometer, anemometer, and further, some note of the proximity and nature of nearby air current obstructions. I guess that's a tad overboard ;)



Offline kbellis

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Re: Determining Heights for PWSs
« Reply #26 on: January 06, 2019, 10:50:15 AM »
If you'll look at my Meso site, you'll see three pressures, station, SLP, and altimeter.
https://mesowest.utah.edu/cgi-bin/droman/meso_base.cgi?stn=C2274&unit=0&time=LOCAL&product=&year1=2018&month1=2&day1=15&hour1=12&hours=24&graph=0&past=0

Jim, I looked at the information for your site and wondered if I'm seeing this correctly:
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Offline kbellis

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Re: Determining Heights for PWSs
« Reply #27 on: January 06, 2019, 10:56:53 AM »
And if that is your Davis weather station, its elevation at grade shown below is based on lidar data and should be pretty good. I can't speak to what the design specs called for when it was flown, but for our stuff flown in 2010, we had specified 15cm which translates to a statistical 95% confidence when delivering 2' contours.

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Offline CW2274

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Re: Determining Heights for PWSs
« Reply #28 on: January 06, 2019, 01:25:21 PM »
now you are saying media outlets are interested in QNH? NO wonder some get a tad confused with barometric pressure which for most purposes all people want to know is , it is steady or it is rising/falling and would that be fast or slow, everyday people listening to the media don't need the QNH area forecast, they ain't interested and wouldn't know what to do with it in any case
Media outlets have been using airport data as long as I can remember across the entire nation. What do they use where you live???

I'm glad you know "everyday people" and that they're too uneducated to understand the same pressure measurement that's been fed to them for decades. Speak for yourself.

Offline CW2274

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Re: Determining Heights for PWSs
« Reply #29 on: January 06, 2019, 01:27:20 PM »
If you'll look at my Meso site, you'll see three pressures, station, SLP, and altimeter.
Hmmm, I'm seeing four:
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Yeah, I obviously left out the 1500 meter one.

Offline CW2274

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Re: Determining Heights for PWSs
« Reply #30 on: January 06, 2019, 01:37:21 PM »
If you'll look at my Meso site, you'll see three pressures, station, SLP, and altimeter.
https://mesowest.utah.edu/cgi-bin/droman/meso_base.cgi?stn=C2274&unit=0&time=LOCAL&product=&year1=2018&month1=2&day1=15&hour1=12&hours=24&graph=0&past=0

Jim, I looked at the information for your site and wondered if I'm seeing this correctly:
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:shock: :shock: :shock: I'm not sure, but I think I feel violated...That's exactly where my ISS is. My anny is in the left corner of the wall up a pole and my RW tipper is at the bend of the wall on the right, hardwired to the ISS.
I've never been able to see my ISS from space before. :shock: :shock: :shock:
You even got my name right.....

Offline CW2274

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Re: Determining Heights for PWSs
« Reply #31 on: January 06, 2019, 01:42:29 PM »
And if that is your Davis weather station, its elevation at grade shown below is based on lidar data and should be pretty good. I can't speak to what the design specs called for when it was flown, but for our stuff flown in 2010, we had specified 15cm which translates to a statistical 95% confidence when delivering 2' contours.

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Well whatta ya know, that is the exact elevation I have dialed in at the console, 2412' MSL. Whether that's the exact height of it, I made an educated guess...

Offline kbellis

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Re: Determining Heights for PWSs
« Reply #32 on: January 06, 2019, 01:58:07 PM »
Pima County has a wonderful GIS department, and most importantly, USGS has made lidar acquired data more convenient to access than ever. Here's more from your neighborhood on SRTM Worldwide Elevation Data (1-arc-second Resolution, SRTM Plus V3)

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Offline saratogaWX

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Re: Determining Heights for PWSs
« Reply #33 on: January 07, 2019, 11:27:00 AM »
I have truncated this topic and moved all the responses after this one to a new (locked) topic as an example of bad behavior amongst the participants.  You all know better.  The off-topic and rude comments are not conducive to discussion and create a hostile discussion environment.  Please refrain from that type of posting in the future.

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Offline kbellis

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Re: Determining Heights for PWSs
« Reply #34 on: January 12, 2019, 01:39:40 PM »
Many people, including myself, are surprised to learn that in most personal weather stations, the barometer sensor is located in the display console. I think there may be some exceptions with Rainwise equipment; however, I haven't looked into it very much yet. I did have an interesting, albeit brief, conversation with Richie, who worked for 7 years at the Bar Harbor factory and later when Rainwise moved to Trenton into the former Display Concepts building. He mentioned the barometric sensor was "soldered inline" somewhere up on the rooftop mounted unit at the Ellsworth Wastewater Treatment Plant (where Richie now works), and wasn't inside on the rather retro looking display console.

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The discussion of barometer height gets no attention in the CWOP metadata, just as one example. There is mention of the station's location, often simply referred to as the station's elevation. The presumption is that the elevation is at grade. The CWOP Guide, v1.0 20050308, D. Helms, isn't all that fussy in obtaining an elevation, and nothing is ever said in particular regard to the barometric sensor.

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and reading a little further...

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If you own a personal weather and happen to live within a 12-mile radius of Ellsworth, I'll be happy to provide you with a surveyed benchmark.

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