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

Benedikt Hallinger beni at hallinger.org
Tue Oct 6 08:13:20 CEST 2020


Couldn't this be just some data file in the therion installation 
directory?
This could be replaced by any means (like copying yourself, for instance 
and fallback). An online updater would be cool, tough.

Am 2020-10-06 3:34, schrieb Wookey:
> On 2020-10-05 23:54 +0200, Matthias Keller wrote:
>>    Exactly this.
>> 
>>    Unfortunately, even the current Therion 5.5.1 doesn't have a more
>>    meaningful (and correct) message than "unable to determine magnetic
>>    declination for undated surveys"
> 
> I thought this might be a proj confusing error message, but it is 
> therion's.
> 
>>    I would propose:
>> 
>>     1. If a survey is dated but is newer than available correction 
>> data,
>>        build should fail with a message like:
>>        "Error determining magnetic declination for survey <name> with 
>> date
>>        <date>. Please specify the declination explicitly using for 
>> example
>>        'declination 3 deg'"
>>        instead of the (completely wrong)
>>        "unable to determine magnetic declination for undated surveys"
>>     2. If at least one of the imported (and thus joined) surveys has 
>> magnetic
>>        data but at least one does not (or cannot be determined), an 
>> error
>>        shall be thrown as well, because mixing corrected and 
>> uncorrected
>>        surveys is just plain wrong and causes a lot of confusion (as 
>> it has
>>        happened to me). The same error message shall be displayed and 
>> the
>>        build fails.
> 
> This does seem reasonable behaviour. And I agree the error message is
> wrongly worded or issued here.
> 
> I just had a look at the code that produces this error but it's rather
> confusing. A bitmap is used to record what declination data was used
> and if bits 1 and 3 are set you get the above error. I think bit 2 is
> 'used igrf model to get delination' and bit 3 is 'used defined
> declination', and bit 3 is 'didn't use any', but I'm not sure and I
> don't see why two bits would be set. I'll leave it to Martin/Stacho to
> work out how the logic should run here.
> 
> 
>>    Is this the right place to request that or shall I open an issue on
>>    github?
> 
> I think this list is the canonical place to discuss such things.
> 
>>    I really find this issue pressing, because I just cannot imagine, 
>> that
>>    this doesn't happen to everyone here from time to time - keeping 
>> therion
>>    up to date is not the same cycle as adding new surveys, and 
>> suddenly you
>>    fall out of the prediction data.
> 
> This is really an issue of the geomag model. It does work some way
> into the future, but there is a cutoff. Looks like it does 10 years
> into the future as the latest data in the therion source (igrf12) ends
> in 2015 and the previos igrf11 (used in therion 5.4.4) ended in
> 2010. igrf13 (with data to 2020) was released in December 2019
> https://www.ngdc.noaa.gov/IAGA/vmod/coeffs/igrf13coeffs.txt
> 
> So clearly this will arise anytime you have survey data 10 years newer
> than the model in the therion you are running, which as they are only
> released every 5 years and therion may take a year or two to update
> and the installed one may be a few years old, is quite likely to
> happen from time to time, especially in years ending with 0 or 5.
> 
>>    btw, is there any way to update the data in an existing therion
>>    installation? Or is the only way the update to a (hopefully 
>> existing) new
>>    version?
> 
> There could be - the files are available online so therion could use
> the currently-installed version of the file. But currently the igrf
> coefficients file is compiled-in as thgeomagdata.h This means therion
> can always find the data, but it's not updateable without
> recompiling. I could fix this for linux relatively easily, but it's
> harder on Windows. (and it was making things work on windows that
> caused therion to compile-in all the stuff it needed from subsystems,
> many years ago). 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. 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.)
> 
> 
> Wookey
> _______________________________________________
> Therion mailing list
> Therion at speleo.sk
> https://mailman.speleo.sk/listinfo/therion



More information about the Therion mailing list