astronomyengine (version 0.1.0)

astro_observer_vector: Observer position vector from geographic coordinates

Description

Calculates the geocentric equatorial position vector of an observer on the surface of the Earth, taking into account the Earth's rotation. This is the inverse function of astro_vector_observer().

Usage

astro_observer_vector(time, latitude, longitude, height, of_date = FALSE)

Value

A list with components:

x

Equatorial x-coordinate in AU

y

Equatorial y-coordinate in AU

z

Equatorial z-coordinate in AU

t

The time (POSIXct) at which the vector is valid

status

Status code (0 = success)

The vector represents the displacement from Earth's center to the observer, expressed in Astronomical Units (AU). Multiply by #KM_PER_AU to convert to kilometers.

Arguments

time

A POSIXct date and time for which to calculate the observer's position vector.

latitude

The geographic latitude of the observer in degrees north of the equator (range: -90 to +90).

longitude

The geographic longitude of the observer in degrees east of the prime meridian (range: 0 to 360 or -180 to +180).

height

The elevation of the observer above sea level in meters.

of_date

Logical. If TRUE, uses equator-of-date coordinates (Earth's equator at the given time). If FALSE (default), uses J2000 coordinates (Earth's equator on 2000-01-01).

Examples

# Get observer position at Sydney Observatory
time <- as.POSIXct("2024-01-01 12:00:00", tz = "UTC")
obs_vec <- astro_observer_vector(time, latitude = -33.8688, longitude = 151.2093, height = 0)
obs_vec