As you might already know, zmanim (for Shabbos, etc.) are determined by a number of factors, one being the elevation of the particular locale. But for some reason, if you check the charts and algorithms for the zmanim of New York (I'm thinking Monsey (elevation 548 feet), specifically), the elevation is not factored into the times. Any idea why this is? I know the difference would be nominal at best, but it's still a difference. We might as well use it, right? Any ideas why we don't?