Hi Ishikawa-san -.)
Yoshino never struck me as enough of a science geek to think of doing those things. (And Hakaze had virtually no normal education.)
And given that they were out of time sequence, the daylight hours and sunrise sunset times wouldn't have synced anyway.
And my assumption is that Samon's masking spell worked against aerial discovery too, satellite photos wouldn't show it.
Plus, Mahiro wasn't at all interested in helping Hakaze - he only wanted to find Aika's killer.
Zetsuen no Tempest is also one of my all time favourite anime series (along with the manga, which is very good in its own way.)
Dave Baranyi