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decs

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How would i calculate the shortest or longest day for a specific point on earth?

cheers.

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- Thread starter decs
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- #1

decs

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How would i calculate the shortest or longest day for a specific point on earth?

cheers.

- #2

Zurtex

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- #3

radou

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ever heard of www.google.com ?

- #4

decs

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Zurtex said:

i have absolutely no data about any of the prior. what i DO have is various cities locations and the amount of daylight they experienced on the 4th of July.

I should be able to extend these findings to make a generalisation about the hours of daylight for any latitude and longitude.

there should be a relationship that relates the day of the year, the hours of daylight, the latitude and the longitude.

- #5

Zurtex

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Yeah, I wouldn't imagine it's all that complex but you need to know a bit about ellipses and spheres.decs said:i have absolutely no data about any of the prior. what i DO have is various cities locations and the amount of daylight they experienced on the 4th of July.

I should be able to extend these findings to make a generalisation about the hours of daylight for any latitude and longitude.

there should be a relationship that relates the day of the year, the hours of daylight, the latitude and the longitude.

However by the sounds of it you don't really have the mathematical knowledge to construct a method to work out day light given the latitude and longitude and the date. There are calculators all over the web that will just give an output for you though, like the above poster says, you could just use Google.

- #6

decs

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12+(12/67)*latitude*cos(2pi.t)=hours of sunlight

where t=days/365

its ALMOST right ppl...

- #7

Zurtex

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May I ask how you derived that? I may be able to help you.decs said:

12+(12/67)*latitude*cos(2pi.t)=hours of sunlight

where t=days/365

its ALMOST right ppl...

Edit: Oh and it clearly isn't right as it wouldn't work for extreme places like such as the north and south poles where there can be daylight for days.

I speant about 5 minuites attempting to draw out a model to caclulate it when I realized quite a lot of data. Anyway here is something I found while looking it up: http://www.spsu.edu/math/stinger/101-115/109.htm

I have a feeling that is a bit simplified but I think it might do you nicely.

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- #8

uart

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I remembering figuring this one out years ago when I was a student. I'm not sure if the equation I got was exact, but I think it was pretty close. The formula I arrived at was

**daylight_hours = 12 ( 1 + 2/Pi arcsin( tan(tilt) tan(lat) sin(2 Pi * n / 365.25) ) )**

Where,

**tilt** = Constant of 0.4093 radians (23.45 degrees)

**lat** = Latitude of location on Earth.

**n** = Number of days elapsed since the northern hemishpere spring equinox.

Notes.

1. I've used radian throughout, just change each literal occurance of "Pi" to 180 if you want to use degrees throughout.

2. The equation should apply without modification to both northern and southern hemispheres provided that southern latitudes are entered as negative.

Where,

Notes.

1. I've used radian throughout, just change each literal occurance of "Pi" to 180 if you want to use degrees throughout.

2. The equation should apply without modification to both northern and southern hemispheres provided that southern latitudes are entered as negative.

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