Geographic coordinates from observer position vector — astro_vector

Given a geocentric equatorial position vector, calculates the geographic latitude, longitude, and elevation of the observer on Earth's surface. This is the inverse function of astro_observer_vector().

Usage

astro_vector_observer(vector, of_date = FALSE)

Arguments

vector

A list with components representing the observer's position vector:

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

The components are expressed in Astronomical Units (AU). Divide kilometers by #KM_PER_AU to convert to AU.

of_date

Logical. If TRUE, interprets vector as equator-of-date coordinates. If FALSE (default), interprets it as J2000 coordinates.

Value

A list with components:

latitude: Geographic latitude in degrees north of the equator (range: -90 to +90)
longitude: Geographic longitude in degrees east of the prime meridian (range: 0 to 360)
height: Elevation above sea level in meters

Examples

# Convert a position vector back to geographic coordinates
obs_vec <- list(
  x = 0.00005, y = 0.00005, z = 0.00005,
  t = as.POSIXct("2024-01-01 12:00:00", tz = "UTC")
)
obs <- astro_vector_observer(obs_vec)
obs
#> $latitude
#> [1] 35.44905
#> 
#> $longitude
#> [1] 124.7278
#> 
#> $height
#> [1] 6584589
#>