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kmz files, accuracy thereof

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#1 Farzad_K

Farzad_K

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Posted 06 October 2023 - 08:29 PM

Hello Folks. I think some of you might find this information useful.

 

If you look at a solar eclipse, for example, and then download the kmz file so you can use it on Gaia or Google Earth you may find that the paths do not match the one shown on the link.

 

I contacted Xavier Jubier and he was kind enough to tell me why the centerlines did not match was because they were outdated although it won't affect most viewing. He also pointed me to his website where I could generate current kmz files and I did it and it worked.

 

Here is his response to my message about the discrepancy issue I discovered:
 

"No issue, it’s just that the deltaT value, which is related to the Earth rotation, used isn’t exactly the same for the pre-generated map and KMZ file. When making maps or KMZ files we have to predict years in advance future values of deltaT. This can induce a path shift in longitude of a couple hundred meters and has zero consequence on your observations unless you aim for the edges.
The KMZ files were generated years ago and I didn’t recreate those with updated deltaT values as for most people it doesn’t matter. The same will happen for 2024, again no meaningful consequences for most observers. Being exactly on the centerline is meaningful, being a kilometer or even a mile away doesn’t change anything to your experience.

However should you wish to have an updated KMZ file you can visit http://xjubier.free.fr/5mcse and generate by yourself an updated KMZ file. Then you’ll see both centerlines will coincide."

 

Although I contacted him about the October Annular eclipse this applies to all eclipses unless he takes the time and update them. I think being more on the center is important for total eclipses than Annular ones.

 

Cheers

 

 

Farzad

 

 


Edited by Farzad_K, 06 October 2023 - 10:45 PM.




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