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Calculating magnetic declination

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#1
Brian Moran

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I know of 2 solutions to finding magnetic declination from true north at a given point on the earth: using the ArcGIS Production Mapping extension tool "Magnetic Calculator", or typing the coordinates into the NOAA online tool.

I have over 100 points I need to calculate this for, so I would prefer not to type each one into the online tool. And I do not have access to the Production Mapping extension, except through a remote Citrix connection environment, in which it throws an error every time and severely raises my blood pressure. I have no idea why such a tool isn't available within the stock Cartography toolbox in ArcGIS... it seems like a pretty basic function.

Anyone know of other options?

#2
Strebe

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I have no idea why such a tool isn't available within the stock Cartography toolbox in ArcGIS... it seems like a pretty basic function.

Anyone know of other options?


I know of no other option. Magnetic declination changes (slowly) over time and is not calculable in the large. Hence it is no surprise there is no (static) tools to deal with it.

Regards,
— daan Strebe

#3
frax

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You could create a little script that uses that NOAA online service and queries and parses for each point in your data. You can send me a private message if you would like a quote for me to set this up for you!
Hugo Ahlenius
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#4
Michael Schmeling

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There is some software for Python and Javascript that claims to calculate magnetic declination:

geomag
Michael Schmeling
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Arid Ocean Map Illustrations
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#5
Brian Moran

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I have no idea why such a tool isn't available within the stock Cartography toolbox in ArcGIS... it seems like a pretty basic function.

Anyone know of other options?


I know of no other option. Magnetic declination changes (slowly) over time and is not calculable in the large. Hence it is no surprise there is no (static) tools to deal with it.

Regards,
— daan Strebe


Thanks. I'm pretty sure the tool in the Production Mapping extension is a static tool, but it is restricted to use for a specific time period of a few years. Perhaps not perfectly accurate, but good enough for many of our purposes... I was referring to that tool when grumbling that it is only available in an extension package.

Thanks for the other replies. The python package looks interesting.

#6
antoniolocandro

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You can search online for NOAA geomag software executable for windows, I assume that the python library is from the same source also but you would need to know or learn a little python to execute it, if you do, then you can just program a function so that ARCGIS queries this python library.

The geomag software has a GUI and you can use it with command line (DOS window), if you want to do a batch of points you need to provide them in a txt file in a specific format (the software provides a few samples), it runs pretty fast last time I used it I got 500 magnetic declination for points in less than a minute.

No need to buy expensive software or re invent the wheel.

I have no idea why such a tool isn't available within the stock Cartography toolbox in ArcGIS... it seems like a pretty basic function.

Anyone know of other options?


I know of no other option. Magnetic declination changes (slowly) over time and is not calculable in the large. Hence it is no surprise there is no (static) tools to deal with it.

Regards,
— daan Strebe


Thanks. I'm pretty sure the tool in the Production Mapping extension is a static tool, but it is restricted to use for a specific time period of a few years. Perhaps not perfectly accurate, but good enough for many of our purposes... I was referring to that tool when grumbling that it is only available in an extension package.

Thanks for the other replies. The python package looks interesting.



#7
antoniolocandro

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The actual geomag link for you to check it out

I know of 2 solutions to finding magnetic declination from true north at a given point on the earth: using the ArcGIS Production Mapping extension tool "Magnetic Calculator", or typing the coordinates into the NOAA online tool.

I have over 100 points I need to calculate this for, so I would prefer not to type each one into the online tool. And I do not have access to the Production Mapping extension, except through a remote Citrix connection environment, in which it throws an error every time and severely raises my blood pressure. I have no idea why such a tool isn't available within the stock Cartography toolbox in ArcGIS... it seems like a pretty basic function.

Anyone know of other options?



#8
Clark Geomatics

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Note that the software calculates values valid between 1900 and 2004 - this will introduce an inaccurate declination if the rate of change is fairly rapid (e.g. for near-polar locations, say Iceland) for your lat/long pair - just a heads-up.
Cheers,

Jeff Clark
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#9
antoniolocandro

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I calculate for 2004-2015 also so GeoMag works fine you would need to select WMM or IGRF for the calculation

Note that the software calculates values valid between 1900 and 2004 - this will introduce an inaccurate declination if the rate of change is fairly rapid (e.g. for near-polar locations, say Iceland) for your lat/long pair - just a heads-up.






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