Great response!
The third notion is HAE in WGS84(G1762), which is essentially the same as ITRF2014. This HAE is different from NAD83 HAE because the ellipsoids have a different origin, but all things NAD83/WGS84 are within about 2m, about 1m horizontally. Compared to anything you can measure with a barometer, that's identical.
I thought WGS84 was a gravity field model. Not sure -- I just assumed.
Yes, I made a loop with two benchmarks and my hand held barometer while comparing to my station's AS (barometric pressure reading). The loop closed perfectly (within a foot), and arriving back home the altimeter read 1078ft (328.6m), so I am very confident I now have the correct ortho height of my WX station. I held the unit right to the sensor, so not ground level but sensor level. I also set the handheld barometer directly on top of the bench marks and checked my home pressure settings since I was not further than a quarter mile returning quickly back home.Your use of a barometric altimeter to transfer elevation from a benchmark to your station makes sense. I would measure at home, go to the mark, meausure, and come home and measure, so you can compare the before/after average with the mid measurement.
I had the same notion, but changed my mind. I do believe that zeroing my station to the QC feedback I am getting from Gladstone (CWOP) is probably the better way to go. I am going to keep tweaking my station pressure calibration until my signal is right in the middle of their signal. My new WeeWx config goes off (and corrects) station pressure. It ignores my AS (barometer) reading. That is probably a good thing because it looks like my WG1000 just adds a Y intercept to the data instead of doing the correct altitude adjusted equation. I am sure the output is close, but that is not just a linear equation or simple addition. I am just going to ignore the airports for now, and when I am done tweaking to CWOP I am confident that on a high pressure day where all the airports agree, my station will match those as well.My impression is that the standard approach is to wait until there is a persistent high pressure with little variance and then compared your (corrected to sea level) barometer with that of nearby official stations and then basically apply an offset. I did that and my configured station height is something that I know believe is off. But I think the combination of aboslute pressure measurement error and height error is close to zero.
Only recently have do I have the ability to measure height accurately. A friend brought over a 25-year-old survey-grade L1/L2 GPS receiver. We set it up and measured for 30h and processed the data vai the NGS. Now, one can do RTK with the u-blox F9P, and be similar. So I continue on my quest for barometer calibration.
A man after my own heart. I purchased a spirit level (surveyor's tansit) so that I could play with benchmarks a few years back. I also have a solar filter for it, so that I can measure off of the Sun's limbs in my reticle. I learned playing with that thing a compass (even when corrected for magnetic declination) is a very inaccurate instrument. I wondered why the azimuth control benchmarks were always off by wildly varying readings. I thought the surveyor's that monumented those benchmarks were sloppy. That was until I used the Sun to find true North. Those benchmarks were accurate right down to the resolving power of the vernier on my transit. Hats off to those guys. Geodesy is serious business, and they know what they are doing. Fascinating discipline. I am a physics professor, and that stuff is right up my alley.
Regards, Chris Maness -- in SoCal.
-- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/0d78822a-625c-b2ee-7469-6ff095071735%40gmail.com.
OpenPGP_0x55BE65AD1B41D696.asc
Description: application/pgp-keys
OpenPGP_signature
Description: OpenPGP digital signature
