+++ /dev/null
-#!/usr/bin/lua
---[[
- Utility to let you figure out if we should've daylight now.
- Usage: ./suntime.lua [debug]
- Exit code is either 0, we have daylight - or 1, no daylight.
- Adjust lon, lat, tolerance for your location and the required
- tolerance in seconds.
-]]
-
--- input values
-lon,lat = "3.1234","51.1234"
-tolerance = 4800
-dateTable = os.date("*t")
-curEpoch = os.time(dateTable)
-year = dateTable["year"]
-month = dateTable["month"]
-day = dateTable["day"]
-
-function force_range(v, max)
- if( v < 0 ) then
- return (v + max)
- elseif( v >= max) then
- return (v - max)
- end
- return v
-end
-
-function daysInMonth(year, month)
- month2days = {"31", "28", "31", "30", "31", "30", "31", "31", "30", "31", "30", "31"}
-
- -- special case February http://www.henk-reints.nl/cal/gregcal.htm
- if(month == 2) then
- -- no century change and can be devided by 4
- if(((year % 100) ~= 0) and ((year % 4) == 0)) then
- month2days[2] = 29
- -- change of a century and can be devided by 400
- elseif(((year % 100) == 0) and ((year % 400) == 0)) then
- month2days[2] = 29
- end
- end
- return month2days[month]
-end
-
---[[ Ported from https://pypi.org/project/suntime/
- which is based on https://stackoverflow.com/questions/19615350/calculate-sunrise-and-sunset-times-for-a-given-gps-coordinate-within-postgresql
- which took the algorithm from https://web.archive.org/web/20161022214335/https://williams.best.vwh.net/sunrise_sunset_algorithm.htm
-
- year: number
- month: number
- day: number
- lon: string, longitude of your location
- lat: string, latitude of your location
- getRiseTime: bool, true -> sunrise time, false -> sunset time
-
- return value: time in Unix epoch
- ]]
-function calc_sun_time(year, month, day, lon, lat, getRiseTime)
- -- constants we need
- TO_RAD = (math.pi/180)
- zenith = 90.8
-
- -- 1. first calculate the day of the year
- N1 = math.floor(275 * month / 9)
- N2 = math.floor((month + 9 ) / 12)
- N3 = ( 1 + math.floor((year - 4 * math.floor(year / 4) + 2) / 3))
- N = N1 - (N2 * N3) + day - 30
-
- -- 2. convert the longitude to hour value and calculate an approximate time
- lonHour=lon/15
-
- if(getRiseTime) then
- t = N + ((6 - lonHour) / 24)
- else
- t = N + ((18 - lonHour) / 24)
- end
-
- -- 3. calculate the Sun's mean anomaly
- M = (0.9856 * t) - 3.289
-
- -- 4. calculate the Sun's true longitude
- L = M + (1.916 * math.sin(TO_RAD*M)) + (0.020 * math.sin(TO_RAD * 2 * M)) + 282.634
- L = force_range(L, 360 ) -- NOTE: L adjusted into the range [0,360)
-
- -- 5a. calculate the Sun's right ascension
- RA = (1/TO_RAD) * math.atan(0.91764 * math.tan(TO_RAD*L))
- RA = force_range(RA, 360 ) -- NOTE: RA adjusted into the range [0,360)
-
- -- 5b. right ascension value needs to be in the same quadrant as L
- Lquadrant = (math.floor( L/90)) * 90
- RAquadrant = (math.floor(RA/90)) * 90
- RA = RA + (Lquadrant - RAquadrant)
-
- -- 5c. right ascension value needs to be converted into hours
- RA = RA / 15
-
- -- 6. calculate the Sun's declination
- sinDec = 0.39782 * math.sin(TO_RAD * L)
- cosDec = math.cos(math.asin(sinDec))
-
- -- 7a. calculate the Sun's local hour angle
- cosH = (math.cos(TO_RAD * zenith) - (sinDec * math.sin(TO_RAD * lat))) / (cosDec * math.cos(TO_RAD * lat))
- if(cosH > 1) then
- -- return None -- The sun never rises on this location (on the specified date)
- print("Sun will never rise here and now.")
- os.exit()
- elseif(cosH < -1) then
- -- return None -- The sun never sets on this location (on the specified date)
- print("Sun will never rise here and now.")
- os.exit()
- end
-
- -- 7b. finish calculating H and convert into hours
- if(getRiseTime) then
- H = 360 - (1/TO_RAD) * math.acos(cosH)
- else
- H = (1/TO_RAD) * math.acos(cosH)
- end
- H = H / 15
-
- -- 8. calculate local mean time of rising/setting
- T = H + RA - (0.06571 * t) - 6.622
-
- -- 9. adjust back to UTC
- UT = T - lonHour
- UT = force_range(UT, 24) -- UTC time in decimal format (e.g. 23.23)
-
- -- 10. Return
- hr = force_range(math.floor(UT), 24)
- min = tonumber(string.format("%.0f", (UT - math.floor(UT))*60))
- if(min == 60) then
- hr = (hr + 1)
- min = 0
- end
-
- -- 10. check corner case https://github.com/SatAgro/suntime/issues/1 and issue 8
- if(hr == 24) then
- hr = 0
- day = (day + 1)
-
- if(day > daysInMonth(year, month)) then
- day = 1
- month = (month + 1)
-
- if(month > 12) then
- month = 1
- year = (year + 1)
- end
- end
- end
-
- return os.time{year=year, month=month, day=day, hour=hr, min=math.floor(min)}
-end
-
--- calculate sunrise and sunset time adjusted by tolerance seconds
-sunrise = (calc_sun_time(year, month, day, lon, lat, true) + tolerance)
-sunset = (calc_sun_time(year, month, day, lon, lat, false) - tolerance)
-
--- debugging aide
-if(arg[1] == "debug") then
- print("Expected sunrise for today in UTC seconds adjusted +", tolerance)
- print(os.date("%c", sunrise))
- print("Expected sunset for today in UTC seconds adjusted -", tolerance)
- print(os.date("%c", sunset))
-end
-
--- return 0 in case we should've daylight, otherwise return 1
-if((curEpoch >= sunrise) and (curEpoch <= sunset)) then
- os.exit(0)
-else
- os.exit(1)
-end
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projects / sven / scripts.git / blobdiff