[Therion] Therion uses wrong declination for surveys 'in the future'

[Wookey]

On 2020-10-06 21:10 +0200, Martin Budaj wrote:

>    On the other hand: is there any need to use the data older than 1900? If
>    yes, we could implement the GUFM1 model covering the period 1590–1890.

We've had to use data back to about 1910 in Ireland but I'm not aware
of anyone needing to go back before 1890. I'm not sure if there is/was
any conventional cave survey data that old. I reckon we are safe to
carry on ignoring it until someone asks.

>    You can't always avoid mixing dated and undated surveys (sometimes the
>    older survey data might be undated), so using the min(survey_dates) as a
>    proxy for undated surveys (and producing a warning as well) should be a
>    reasonable approach.

Very good point. We have a lot of data imported from other programs
which ends up with no date. And fake data generated from existing
survey plots also ends up dateless. This is definitely a thing.

>      Ideally it would compile one in but have the ability
>      to read a newer file if provided. But then someone has to write a
>      parser.
> 
>    Not sure if writing the parser is worth the effort, as AFAIK all the real
>    issues with the declination come from the incorrect handling of
>    undated/out-of-range data, not from an outdated model. 
>    Even a model outdated 10 or 15 years should provide very reasonable
>    results.

Agreed.


>      We could also try a little harder not to get 10 years behind
>      again. (5.4.4 was released in May 2019 with a model that expired in
>      mid 2020, when the 2025 model had been available since 2015 (and was
>      included with the next therion release in May 2020). Not sure why the
>      update was not to 2030 as that was available from Dec 2019.)
> 
>    There was actually no 2025 model available since 2015. The models are
>    always for 5-year predictions and there is zero overlap between them. Just
>    to illustrate, here is an overview of the history of publication of IGRF
>    models and their inclusion into Therion

Cheers for the corrections.
(and for the quick fixes). 

Wookey
-- 
Principal hats:  Linaro, Debian, Wookware, ARM
http://wookware.org/
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