getDaylightHours: Calculate the sunrise and sunset hours for a time and place

In MazamaScience/MazamaSatelliteUtils: Utilities for Working with Model and Satellite Data as Rasters

Description

Returns the sunrise and sunset hours for specified dates within a bounding box based on sun ephemerides calculations. Sunrise is calculated using the midpoint of the east edge of the bounding box while sunset is calculated using the midpoint of the west edge.

The bounding box may be specified via any of the following methods:

• Olson timezone, either as part of a POSIXt datetime, or specified via the timezone parameter

• Geographic Bounding Box, either as a vector of floats in c(lonLo, lonHi, latLo,latHi) order, or the return value from sp::bbox(), or raster::extent()

• Longitude and latitude specified in decimal degrees

If more than one of the above are specified, the order of preference for determining the bounding box is:

1. longitude, latitude passed in – location +/- 0.1 degrees

2. bbox passed in – use unchanged

3. timezone passed in – use bbox of the timezone

4. datetime is POSIXct – use bbox of the timezone attribute

Usage

getDaylightHours(
  datetime = NULL,
  longitude = NULL,
  latitude = NULL,
  bbox = NULL,
  timezone = NULL,
  isJulian = FALSE
)

Arguments

datetime	Datetime as a Ymd HMS or Julian formatted string, or a POSIXct.
longitude	Longitude of the location in decimal degrees E.
latitude	Latitude of the location in decimal degrees N.
bbox	Bounding box for the region.
timezone	Timezone used to interpret datetime.
isJulian	Logical flag determining whether datetime should be interpreted as a Julian date with day of year as a decimal number. Defaults to FALSE.

Value

List containing POSIXct sunrise and sunset times for the specified date.

Examples

library(MazamaSatelliteUtils)
library(MazamaSpatialUtils)

# Get sunrise and sunset by lat/lon and datetime
getDaylightHours(
  datetime = "2019-09-06", 
  longitude = -123.245, 
  latitude = 42.861
)

# Get sunrise and sunset by bbox and datetime
getDaylightHours(
  datetime = "2019-09-06",
  bbox = c(-124.566, -116.463, 41.991, 46.292) # Oregon
) 

# Get sunrise and sunset by datetime and timezone
getDaylightHours(
  datetime = "2019-09-06",
  timezone = "America/Los_Angeles"
)

# Get sunrise and sunset for a vector of datetimes
getDaylightHours(
  datetime = c("2019-06-21", "2019-09-23", "2019-12-22"),
  longitude = -123.245, 
  latitude = 42.861
)

MazamaScience/MazamaSatelliteUtils documentation built on Dec. 17, 2021, 3:20 a.m.