Magnetic declination
Quick question concerning the magnetic declination. How you indicate it? Just by entering the date or with the command <declination>? Because when I just specify the date, the declination which is calculate is for the first January, even if I specify another month in the centreline (e.g. 28.08.2017). Consequently, centreline is slightly offset that if I enter the real declination for the date. I don’t know if this shift is important for survey accuracy or if I can ignore it ? Thanks and sorry for all my questions. Martin K.
Hi, declination should be calculated automatically based on the survey date. Declination parameter is for manual correction. \LB 2. 3. 2018 v 16:29, Martin KERN via Therion <therion@speleo.sk>:
Quick question concerning the magnetic declination.
How you indicate it?
Just by entering the date or with the command <declination>?
Because when I just specify the date, the declination which is calculate is for the first January, even if I specify another month in the centreline (e.g. 28.08.2017). Consequently, centreline is slightly offset that if I enter the real declination for the date.
I don’t know if this shift is important for survey accuracy or if I can ignore it ?
Thanks and sorry for all my questions.
Martin K.
_______________________________________________ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Thanks for your reply Ladislav. I know that but the automatic declination is calculated for the first januray of the year which is enter, not for the exact date. It's not a probleme for the accuracy of the survey ? Martin K. Le 2 mars 2018 17:05, "Ladislav Blažek" <ladislav@lblazek.cz> a écrit :
Hi,
declination should be calculated automatically based on the survey date. Declination parameter is for manual correction.
\LB
2. 3. 2018 v 16:29, Martin KERN via Therion <therion@speleo.sk>:
Quick question concerning the magnetic declination.
How you indicate it?
Just by entering the date or with the command <declination>?
Because when I just specify the date, the declination which is calculate is for the first January, even if I specify another month in the centreline (e.g. 28.08.2017). Consequently, centreline is slightly offset that if I enter the real declination for the date.
I don’t know if this shift is important for survey accuracy or if I can ignore it ?
Thanks and sorry for all my questions.
Martin K.
_______________________________________________ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
Hi Martin, Just to be sure, but I guess you already know it, you also have to enter the coordinate for the calculation of the declination. Phil
On 02 Mar 2018, at 17:22 PM, Martin KERN via Therion <therion@speleo.sk> wrote:
Thanks for your reply Ladislav.
I know that but the automatic declination is calculated for the first januray of the year which is enter, not for the exact date. It's not a probleme for the accuracy of the survey ?
Martin K.
Le 2 mars 2018 17:05, "Ladislav Blažek" <ladislav@lblazek.cz <mailto:ladislav@lblazek.cz>> a écrit : Hi,
declination should be calculated automatically based on the survey date. Declination parameter is for manual correction.
\LB
2. 3. 2018 v 16:29, Martin KERN via Therion <therion@speleo.sk <mailto:therion@speleo.sk>>:
Quick question concerning the magnetic declination.
How you indicate it?
Just by entering the date or with the command <declination>?
Because when I just specify the date, the declination which is calculate is for the first January, even if I specify another month in the centreline (e.g. 28.08.2017). Consequently, centreline is slightly offset that if I enter the real declination for the date.
I don’t know if this shift is important for survey accuracy or if I can ignore it ?
Thanks and sorry for all my questions.
Martin K.
_______________________________________________ Therion mailing list Therion@speleo.sk <mailto:Therion@speleo.sk> https://mailman.speleo.sk/listinfo/therion <https://mailman.speleo.sk/listinfo/therion>
Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
The variation throughout the year is fairly minimal and I don’t believe it is statistically relevant to worry about the data collection month. Henry From: Therion [mailto:therion-bounces@speleo.sk] On Behalf Of Martin KERN via Therion Sent: 02 March 2018 16:22 To: Ladislav Blažek <ladislav@lblazek.cz> Cc: Martin KERN <martin.dehautenbas@gmail.com>; List for Therion users <therion@speleo.sk> Subject: Re: [Therion] Magnetic declination Thanks for your reply Ladislav. I know that but the automatic declination is calculated for the first januray of the year which is enter, not for the exact date. It's not a probleme for the accuracy of the survey ? Martin K. Le 2 mars 2018 17:05, "Ladislav Blažek" <ladislav@lblazek.cz<mailto:ladislav@lblazek.cz>> a écrit : Hi, declination should be calculated automatically based on the survey date. Declination parameter is for manual correction. \LB 2. 3. 2018 v 16:29, Martin KERN via Therion <therion@speleo.sk<mailto:therion@speleo.sk>>: Quick question concerning the magnetic declination. How you indicate it? Just by entering the date or with the command <declination>? Because when I just specify the date, the declination which is calculate is for the first January, even if I specify another month in the centreline (e.g. 28.08.2017). Consequently, centreline is slightly offset that if I enter the real declination for the date. I don’t know if this shift is important for survey accuracy or if I can ignore it ? Thanks and sorry for all my questions. Martin K. _______________________________________________ Therion mailing list Therion@speleo.sk<mailto:Therion@speleo.sk> https://mailman.speleo.sk/listinfo/therion Dell Corporation Limited is registered in England and Wales. Company Registration Number: 2081369 Registered address: Dell House, The Boulevard, Cain Road, Bracknell, Berkshire, RG12 1LF, UK. Company details for other Dell UK entities can be found on www.dell.co.uk.
If I remember correctly, the declination is displayed on the log file for the beginning of all the years for which you have some survey data, but it is interpolated in between these measurements with the exact date for each survey environment where you provided a date. Xavier Le 02-Mar-18 à 17:22, Martin KERN via Therion a écrit :
Thanks for your reply Ladislav.
I know that but the automatic declination is calculated for the first januray of the year which is enter, not for the exact date. It's not a probleme for the accuracy of the survey ?
Martin K.
Le 2 mars 2018 17:05, "Ladislav Blažek" <ladislav@lblazek.cz <mailto:ladislav@lblazek.cz>> a écrit :
Hi,
declination should be calculated automatically based on the survey date. Declination parameter is for manual correction.
\LB
2. 3. 2018 v 16:29, Martin KERN via Therion <therion@speleo.sk <mailto:therion@speleo.sk>>:
Quick question concerning the magnetic declination.
How you indicate it?
Just by entering the date or with the command <declination>?
Because when I just specify the date, the declination which is calculate is for the first January, even if I specify another month in the centreline (e.g. 28.08.2017). Consequently, centreline is slightly offset that if I enter the real declination for the date.
I don’t know if this shift is important for survey accuracy or if I can ignore it ?
Thanks and sorry for all my questions.
Martin K.
_______________________________________________ Therion mailing list Therion@speleo.sk <mailto:Therion@speleo.sk> https://mailman.speleo.sk/listinfo/therion <https://mailman.speleo.sk/listinfo/therion>
_______________________________________________ Therion mailing list Therion@speleo.sk https://mailman.speleo.sk/listinfo/therion
--
------------------------- Xavier Pennec Senior Research Scientist / Directeur de recherche Asclepios project-team, INRIA Sophia-Antipolis 2004 Route des Lucioles, BP93 F-06902 Sophia-Antipolis Cedex, France +33 4 92 38 76 64 +33 6 78 35 16 90 http://www-sop.inria.fr/asclepios/ -------------------------------
On Fri, Mar 02, 2018 at 05:57:26PM +0100, Radek via Therion wrote:
Here's more accurate
That uses the same model as Therion does, so I can't see why it should be more accurate (unless you're using a version of therion more than a year old, as before https://github.com/therion/therion/pull/52 Therion calculated the fraction of the year to use in a slightly odd way, though even then the difference is tiny if you're specifying a full date). Also, if you look up values by hand and specify them explicitly to therion you are hard coding the answers for the current version of the IGRF model. But each generation of the IGRF model is necessarily predictive for dates after it was issued and is only declared to be definitive for dates more than 5 years before it was issued. So each new generation of the model can change the declination figures reported for the last 10 years compared to the previous generation (and the new answers should be expected to be better). As Xavier suggests, the table of reported declinations in the log is for the start of each year, but declinations used for surveys are calculated for the actual survey dates. Maybe this needs making clearer somehow, as this isn't the first time this summary table has led someone to think that the declination was only being calculated for the start of each year: https://mailman.speleo.sk/pipermail/therion/2017-February/006241.html Cheers, Olly
participants (7)
-
Henry.Bennett＠dell.com -
Ladislav Blažek -
Martin KERN -
Olly Betts -
Philippe Vernant -
Radek -
Xavier Pennec