I read Gone's question differently in that I thought he was assuming that 
because the altimeter had not been set in the console the barometer 
readings issued by the station would have been incorrect up to the time he 
entered the altitude in the station, and he wanted to be able to calculate 
what they should have been by adjusting them in his database for the 
correct altitude - for which he wanted to know the formula to be used.  

But I see from the hardware manual that although barometer is supplied by 
the station the altimeter and pressure vslues in weewx are software derived 
- implying that these will also be incorrect following any adjustments to 
barometer.  Maybe I just totally misunderstood the original problem (as 
well as what a Vantage actually outputs)!!


On Wednesday, 11 January 2017 15:29:47 UTC+2, Tom Keffer wrote:

> ​You didn't say what kind of database, but assuming it's sqlite... 
>
> You also didn't say what installation method you used, but assuming it's 
> setup.py...
>
> Make a backup of your sqlite database
>
> *cd /home/weewx*
> *cp archive/weewx.sdb archive/weewx.sdb.backup*
>
>
> Install the utility sqlite3 if it hasn't already been installed:
>
> *sudo apt-get install sqlite3*
>
>
> Use it to patch your database:
>
> *sqlite3 archive/weewx.sdb*
> sqlite> *UPDATE archive SET barometer=barometer+xxx;*
>
> sqlite> *.quit*
>
>
> where xxx is the correction you wish to apply.
>
> Rebuild the daily summaries:
>
> *./bin/wee_database weewx.conf --drop-daily*
> *./bin/wee_database weewx.conf --backfill-daily*
>
>
> -tk
>
>
> ​
>
> On Tue, Jan 10, 2017 at 10:59 PM, Gone Bush <[email protected] 
> <javascript:>> wrote:
>
>> The problem: I've had my Vantage Pro2 for a couple of months and finally 
>> got round to configuring the altitude in the console.
>>
>> (The Setup function  doesn't step through that option.)
>>
>> Now what I want to do is correct the historical barometric data.
>>
>> So, to my question: What is the formula that will do that? (Google has 
>> failed me.)
>>
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