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wmo-im / iwxxm

XML schema and Schematron for aviation weather data exchange
https://old.wmo.int/wiswiki/tiki-index.php%3Fpage=TT-AvXML
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IWXXM SWX. Day light side and coordinates accuracy #222

Closed moryakovdv closed 4 years ago

moryakovdv commented 4 years ago

Hello. Converting the SWX Advisory I'm facing with DAYLIGHT SIDE. As it mentioned in TAC-to-XML-Guidance.txt we should provide lat/lon of the sub-solar point as a center of the area for the given date-time. AFAIK, the latitude of the sub-solar point is the same as solar declination for the given time(correct me, please, if I'm wrong). In common engineering calculation we calc this value for the given day. So, the latitude changes when the day changes. But, in our IWXXM examples the latitude changes during the day. So I wonder is the accuracy of latitude enough (daily changes) when we use the common approach or one should use more precise calculations to inject hour correction? Might be we should mention it in guidance?

Regards, Dmitry

blchoy commented 4 years ago

Finding the sub-solar point at a particular time is a well known problem and there are details on calculating the location of the point. I would suggest we go for a more precise calculation.

If you think the guidance is not clear enough we can update this in version 3.0.1.

blchoy commented 4 years ago

Reading the guidance again I believe the message should be clear enough. Until there are better suggestions this issue will be closed.