Sun Settings - Local vs Solar Time

j0258169 — Tue, 24 Oct 2017 16:31:57 GMT

The Time in the Sun Settings seems to be solar time, not local time. I have a supposedly accurate sundial modeled, to display local time. When I tried running Single Day studies at one hour intervals with the time set to the hour, the sundial doesn't seem to be accurate. When I compensate the time for a local to solar time conversion, I seem to be getting more accurate results.. Can anyone confirm? I can't seem to find this behavior documented anywhere.

The only documentation I found is here:

About the Sun Path

"Note: The times displayed in the sun path and Sun Settings dialog are in local time for your project location. Because local time can vary from solar time by an hour or more, depending on your location, the sun's position in the sun path is shown in solar time to ensure that the sun is directly overhead at solar noon."

But this seems to be contrary to what I experienced..

Re: Sun Settings - Local vs Solar Time

rds3000 — Mon, 30 Oct 2017 18:04:46 GMT

You will see some variation in the sun angles due to your site position in relation to the timezone, so keep that in mind. From one end of the timezone to the other, the sun angles can vary by an hour (or more for odd-shaped timezones).

When doing lighting or solar analyses, we use hourly weather data and a timezone mapping that is accurate to a few miles, but you may see some variation at the very edges of timezones. Also remember that the solar weather data is cumulative/average values over the previous hour, so are more-appropriately applied to the half-hour before. We deal with this by interpolation, but keep in mind that quality of weather data, variation over time, etc mean that point-in-time results are less informative than comparing cumulative results over time.

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Sun Settings - Local vs Solar Time

Re: Sun Settings - Local vs Solar Time