If I recall looking @ MADIS 15 minute data, it least for me, the pressure 
of the opposite wave did drop a some before the major spike. After changing 
the colors on the charts, it aligns with the first drop in pressure.

On Thursday, January 20, 2022 at 11:28:41 PM UTC-5 Cameron D wrote:

> There are certainly uncertainties in the barometric data timings. My 
> system is probably a worst case - it only reports a value every 15 minutes, 
> and I don't know if that is an average of the previous 15 minutes or just a 
> snapshot reading at the transition time. So for me 20 minutes is within the 
> uncertainty.
> Also, I don't know if it is expected, but the  pulses that travelled 
> further show only the negative part, which comes after the positive. So 
> there is extra lag in that.
>
> I derived a speed by fitting data to Australian bureau charts, and they 
> only show 30 minute samples, so my speed is hardly definitive.  I would 
> expect it to vary a bit around the globe.  The average speed I derived from 
> the first peak alone was 0.30 m/s, so that is either an indicator of the 
> uncertainty in the fitting or that the average speed increased as it 
> progressed.
> On Friday, 21 January 2022 at 2:05:49 pm UTC+10 [email protected] wrote:
>
>> Yes, the image files are being produced. Only thing I noticed was the 
>> arrival time for the opposite pulse is off by approx. 20 minutes according 
>> to the actual PWS data, this could be due to the wave speeding up or 
>> slowing down as it made its way around the globe.  Right now I'm using your 
>> default settings.
>>
>> On Thursday, January 20, 2022 at 10:40:36 PM UTC-5 Cameron D wrote:
>>
>>> the RankWarning is just a warning, you should still have image files 
>>> produced.  I expect the polyfit it just ignores higher order terms and just 
>>> returns a quadratic.
>>>
>>> That is because the polynomial is a poor representation of the 
>>> background, and the spline fit works better, if you get the parameters 
>>> correct.
>>>
>>> Initially you are better just to view the results without trend 
>>> removal.  If the peaks  do not stand out then  background removal is 
>>> unlikely to help much.
>>> Also, with my code,  make sure you start with oversampling set to 1. 
>>> Only adjust it if you see a stair-step effect.
>>>
>>> On Friday, 21 January 2022 at 1:09:28 pm UTC+10 [email protected] 
>>> wrote:
>>>
>>>> Modified the query and added the print statement as suggested 
>>>> by Cameron D and here are the results:
>>>>
>>>> *Morrowwn Script:*
>>>>
>>>> raspberrypi:~/Desktop/Tonga $ python3 tonga_barometer.py
>>>> distance to eruption 13293.9 km arrival at 1642261629 (2022-01-15 
>>>> 10:47:08)
>>>> select datetime, barometer from archive where datetime > 1642172400 and 
>>>> datetime < 1642693629 order by dateTime;
>>>> Traceback (most recent call last):
>>>>   File "tonga_barometer.py", line 47, in <module>
>>>>     coeff = np.polyfit(xdata, ydata, 2)
>>>>   File "/usr/lib/python3/dist-packages/numpy/lib/polynomial.py", line 
>>>> 590, in polyfit
>>>>     y = NX.asarray(y) + 0.0
>>>> TypeError: unsupported operand type(s) for +: 'NoneType' and 'float'
>>>>
>>>>
>>>> *Cameron D Script*:
>>>>
>>>> raspberrypi:~/Desktop/Tonga $ python3 tonga_baro.py
>>>> distance to eruption 12255.7 km arrival at 1642258384 (2022-01-15 
>>>> 09:53:04)
>>>>       opposite pulse arrival at 1642306911 (2022-01-15 23:21:50)
>>>>       second time around pulse arrival at 1642383509 (2022-01-16 
>>>> 20:38:29)
>>>> query returned 96 data points
>>>> query returned 96 data points
>>>> query returned 95 data points
>>>> tonga_baro.py:108: RankWarning: Polyfit may be poorly conditioned
>>>>   coeff = np.polyfit(xdata, ydata, 5 )
>>>>
>>>> Note: LAT/Long and speed of sound are identical in both scripts.
>>>> On Thursday, January 20, 2022 at 9:27:13 PM UTC-5 Cameron D wrote:
>>>>
>>>>> and add a debug printout for how many result lines there are after ...
>>>>>     result = cursor.fetchall()
>>>>> add the line:
>>>>>     
>>>>> *print( "query returned {} data points".format(len(result)))*
>>>>>
>>>>> On Friday, 21 January 2022 at 12:21:59 pm UTC+10 Cameron D wrote:
>>>>>
>>>>>> To eliminate NULL data points use a query like:
>>>>>> select datetime, barometer from archive where datetime > 1642172400 
>>>>>> and datetime < 1642693629* and barometer is not null *order by 
>>>>>> dateTime;
>>>>>>  You could add the part in bold into the query in the python script.
>>>>>>
>>>>>> Of course, if they are all null...
>>>>>>
>>>>>> On Friday, 21 January 2022 at 12:14:44 pm UTC+10 [email protected] 
>>>>>> wrote:
>>>>>>
>>>>>>> Download the latest script from 
>>>>>>> https://github.com/morrowwm/weewx_tonga_browse. Beside installing 
>>>>>>> the Python Modules Vince stated above, I needed to also install  
>>>>>>> python3-scipy. I do have data between 1642172400 and 1642693629; 
>>>>>>> except for a couple "null" in that time period.   So when I run the 
>>>>>>> script, 
>>>>>>> I get the following error.
>>>>>>>
>>>>>>> raspberrypi:~/Desktop/Tonga $ python3 tonga_barometer.py
>>>>>>> distance to eruption 13293.9 km arrival at 1642261629 (2022-01-15 
>>>>>>> 10:47:08)
>>>>>>> select datetime, barometer from archive where datetime > 1642172400 
>>>>>>> and datetime < 1642693629 order by dateTime;
>>>>>>> Traceback (most recent call last):
>>>>>>>   File "tonga_barometer.py", line 47, in <module>
>>>>>>>     coeff = np.polyfit(xdata, ydata, 2)
>>>>>>>   File "/usr/lib/python3/dist-packages/numpy/lib/polynomial.py", 
>>>>>>> line 590, in polyfit
>>>>>>>     y = NX.asarray(y) + 0.0
>>>>>>> TypeError: unsupported operand type(s) for +: 'NoneType' and 'float'
>>>>>>>
>>>>>>> There should be a way to check for "null" data within the time 
>>>>>>> period.
>>>>>>> On Thursday, January 20, 2022 at 8:12:55 PM UTC-5 Cameron D wrote:
>>>>>>>
>>>>>>>> yes, definitely looks like there is no data.
>>>>>>>> I have attached another version of mine, in which the trend line is 
>>>>>>>> disabled by default, but I suspect that would just delay the 
>>>>>>>> inevitable and 
>>>>>>>> it would crash trying to do the plot.
>>>>>>>>
>>>>>>>> I also fixed up a few plotting errors in my code to do with the 
>>>>>>>> mysteries (to me) of layer ordering.
>>>>>>>> I also had a background bar showing either side of expected arrival 
>>>>>>>> - in this version I have now changed that to start at the expected 
>>>>>>>> arrival 
>>>>>>>> and stop 1 hour later.
>>>>>>>>
>>>>>>>> On Friday, 21 January 2022 at 3:29:36 am UTC+10 [email protected] 
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hello,
>>>>>>>>> Not being a programmer, I probably shouldn't have messed with 
>>>>>>>>> this, but being curious...
>>>>>>>>>
>>>>>>>>> I tried the code posted on github as well as the one by Cameron D. 
>>>>>>>>> In both cases I got the following error:
>>>>>>>>> ```
>>>>>>>>> root@n4mrv:/home/bg/weewx_tonga_browse-main# python3 ./tonga.py   
>>>>>>>>> [file 
>>>>>>>>> from Cameron D]
>>>>>>>>>
>>>>>>>>> distance to eruption 12056.6 km arrival at 1642258360 (2022-01-15 
>>>>>>>>> 09:52:39)
>>>>>>>>>       opposite pulse arrival at 1642308921 (2022-01-15 23:55:21)
>>>>>>>>>       second time around pulse arrival at 1642385471 (2022-01-16 
>>>>>>>>> 21:11:10)
>>>>>>>>> Traceback (most recent call last):
>>>>>>>>>   File "./tonga.py", line 178, in <module>
>>>>>>>>>     plot_burst( cursor, arrival_time, hour_span, "primary" )
>>>>>>>>>   File "./tonga.py", line 54, in plot_burst
>>>>>>>>>     coeff = np.polyfit(xdata, ydata, background_order )
>>>>>>>>>   File "<__array_function__ internals>", line 180, in polyfit
>>>>>>>>>   File 
>>>>>>>>> "/usr/local/lib/python3.8/dist-packages/numpy/lib/polynomial.py", 
>>>>>>>>> line 638, 
>>>>>>>>> in polyfit
>>>>>>>>>     raise TypeError("expected non-empty vector for x")
>>>>>>>>> TypeError: expected non-empty vector for x
>>>>>>>>> ```
>>>>>>>>> I added my lat/lon information but may have missed something else 
>>>>>>>>> I need to change. Python modules were installed as directed. Copy of 
>>>>>>>>> weewx.sdb is in the same directory as the program.
>>>>>>>>> Thanks.
>>>>>>>>> Bob
>>>>>>>>> On Wednesday, January 19, 2022 at 10:32:49 AM UTC-5 
>>>>>>>>> [email protected] wrote:
>>>>>>>>>
>>>>>>>>>> On Wednesday, January 19, 2022 at 12:42:04 a.m. UTC-4 Cameron D 
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>    - as you get closer to the equator, tidal changes dominate 
>>>>>>>>>>>    the baseline in that timescale - I tried higher order 
>>>>>>>>>>> polynomials, but they 
>>>>>>>>>>>    are next to useless.
>>>>>>>>>>>
>>>>>>>>>>> I also had little luck with higher order polynomials to remove 
>>>>>>>>>> the general trend.
>>>>>>>>>>
>>>>>>>>>> I've put the script here: 
>>>>>>>>>> https://github.com/morrowwm/weewx_tonga_browse
>>>>>>>>>>
>>>>>>>>>

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