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<p><font face="Helvetica, Arial, sans-serif">Exactly this.</font></p>
<p><font face="Helvetica, Arial, sans-serif">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"<br>
</font></p>
<p><font face="Helvetica, Arial, sans-serif">One can argue whether 0
or an extrapolated value would be better, but failing with a
good error message would be the best way to handle this.
Assuming 0 for undated surveys is probably sensible, however
mixing surves with available data and without data is always
just plain wrong (except if you're living exactly where the
magnetic derivation is 0° ;) ) and should fail.</font></p>
<p><font face="Helvetica, Arial, sans-serif">I would propose:</font></p>
<ol>
<li><font face="Helvetica, Arial, sans-serif">If a survey is dated
but is newer than available correction data, build should fail
with a message like:<br>
"Error determining magnetic declination for survey
<name> with date <date>. Please specify the
declination explicitly using for example 'declination 3 deg'"<br>
instead of the (completely wrong)<br>
"unable to determine magnetic declination for undated surveys"</font></li>
<li><font face="Helvetica, Arial, sans-serif">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.</font></li>
</ol>
<p><font face="Helvetica, Arial, sans-serif">Is this the right place
to request that or shall I open an issue on github?</font></p>
<p><font face="Helvetica, Arial, sans-serif">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.</font></p>
<p><font face="Helvetica, Arial, sans-serif">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?</font></p>
<p><font face="Helvetica, Arial, sans-serif">Thanks</font></p>
<p><font face="Helvetica, Arial, sans-serif">Matt</font><br>
</p>
<div class="moz-cite-prefix">On 05.10.2020 21:38, Benedikt Hallinger
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:2F6A9F62-15F2-4880-BFDC-012808522B38@hallinger.org">
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<div dir="ltr">Falling hard with an appropriate error message
would be good: it’s obvious then that the available data is
invalid, and why. And the message should include the hint to the
declination command to fix this.</div>
<div dir="ltr"><br>
<blockquote type="cite">Am 05.10.2020 um 20:40 schrieb Bruce
Mutton <a class="moz-txt-link-rfc2396E" href="mailto:bruce@tomo.co.nz"><bruce@tomo.co.nz></a>:<br>
<br>
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<p class="MsoNormal">Hi Matt<o:p></o:p></p>
<p class="MsoNormal">I think these issues have been raised
previously.<o:p></o:p></p>
<p class="MsoNormal">The error message for dates later than
those included in the Therion model was inaccurate, as you
point out. I ‘think’ that in recent versions this may
have been replaced with a more meaningful message.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">And then the question of whether it is
better for Therion to extrapolate future declinations, or
set them to zero?<o:p></o:p></p>
<p class="MsoNormal">Shades of failing gracefully or
abruptly, I guess. I could take either side, but I think
my preference would be for Therion to set declinations
beyond those modelled to zero. This way it is more likely
that users will detect the problem (as you have), and
either upgrade to a more recent version of Therion, or
manually set the declination for each affected survey,
using the declination statement.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Bruce<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span
lang="EN-US"> Therion
<a class="moz-txt-link-rfc2396E" href="mailto:therion-bounces@speleo.sk"><therion-bounces@speleo.sk></a> <b>On Behalf Of </b>Matthias
Keller<br>
<b>Sent:</b> Monday, 5 October 2020 21:40<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:therion@speleo.sk">therion@speleo.sk</a><br>
<b>Subject:</b> [Therion] Therion uses wrong
declination for surveys 'in the future'<o:p></o:p></span></p>
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</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p><span
style="font-family:"Helvetica",sans-serif">Hi</span><o:p></o:p></p>
<p><span
style="font-family:"Helvetica",sans-serif">I
just had the following problem: A current survey (with
survey dates 2020.06.27 and 2020.09.19) was compiled
using Therion 5.4.4 (from 2019). I got the following
warning during compilation:</span><o:p></o:p></p>
<p>warning -- unable to determine magnetic declination for
undated surveys<o:p></o:p></p>
<p>However, firstly: this warning is wrong, as all surveys
are dated correctly.<o:p></o:p></p>
<p>However I was stunned by some large loop errors in the
newest surveys (>60cm in only 10 legs). Then, just by
some other impulse I updated therion to 5.5.1 and
suddenly, those errors went down to <10cm and the
generated models looked differently. Also, the above error
message was not present anymore.<o:p></o:p></p>
<p>So i experimented and just added "declination 3 deg" to
the two new surveys (from June and September) and
suddenly, the output generated by 5.4.4 looked pretty much
as the one from 5.5.1<o:p></o:p></p>
<p>It appears that, when therion cannot determine the
magnetic declination of a survey (with valid date!), it
finally just assumes 0. The problem seems to be, that the
declination data stored in 5.4.4 didn't let therion
determine a possible declination for 2020.06.27 and
2020.09.19 so it just assumed 0. I would have expected
therion to at least consider the latest known declination
which would result to around 3° (in Switzerland).<o:p></o:p></p>
<p>Is this a known issue? It just means that whenever you
open a survey in some version being 'too old', it will
kill your plans...<o:p></o:p></p>
<p>BTW, Therion 5.4.4 seems to have *some* data for 2020 at
least, as it seems:<o:p></o:p></p>
<p>geomag declinations (deg):<br>
2019.1.1 2.9201<br>
2020.1.1 3.0503<o:p></o:p></p>
<p>but the only surveys from 2020 are the ones from June
2020 and September 2020, and both were assigned a
declination of 0° instead of about 3°. I can verify that
by adding the declination parameter with "0 deg" to those
surveys and the output is identical to the one without
this parameter.<o:p></o:p></p>
<p>Thanks<o:p></o:p></p>
<p>Matt<o:p></o:p></p>
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