geographiclib (version 0.4.1)

georef_fwd: World Geographic Reference System (Georef)

Description

Convert geographic coordinates (longitude/latitude) to World Geographic Reference System (Georef) codes, or convert Georef codes back to coordinates.

Usage

georef_fwd(x, precision = 2L)
georef_rev(georef)

Value

• georef_fwd(): Character vector of Georef codes.

• georef_rev(): Data frame with columns:

  • lon: Longitude of cell center in decimal degrees

  • lat: Latitude of cell center in decimal degrees

  • precision: Precision level

  • lat_resolution: Cell half-height in degrees

  • lon_resolution: Cell half-width in degrees

Arguments

x

A two-column matrix or data frame of coordinates (longitude, latitude) in decimal degrees, or a list with longitude and latitude components. Can also be a length-2 numeric vector for a single point.

precision

Integer specifying the precision level (-1 to 11):

• -1: 15-degree cells (2-character code)

• 0: 1-degree cells (4-character code)

• 1: 1-minute cells (6-character code)

• 2: 0.1-minute cells (8-character code)

• Higher values give progressively finer precision

georef

Character vector of Georef codes to convert back to coordinates.

Details

The World Geographic Reference System (Georef) is a grid-based geocode system used primarily for air navigation. It was developed by the US and adopted by ICAO (International Civil Aviation Organization).

The Georef code structure:

• First letter: 15° longitude band (A-Z, omitting I and O)

• Second letter: 15° latitude band (A-M, omitting I)

• Third letter: 1° longitude within band (A-Q, omitting I and O)

• Fourth letter: 1° latitude within band (A-Q, omitting I and O)

• Remaining digits: minutes (and fractions) of longitude and latitude

Example: "GJPJ3217" represents approximately (0.54°, 51.28°)

See Also

gars_fwd() for Global Area Reference System, mgrs_fwd() for Military Grid Reference System.

Examples

# Basic conversion
georef_fwd(c(-0.1, 51.5))

# Different precision levels
georef_fwd(c(-0.1, 51.5), precision = -1)  # 15-degree
georef_fwd(c(-0.1, 51.5), precision = 0)   # 1-degree
georef_fwd(c(-0.1, 51.5), precision = 1)   # 1-minute
georef_fwd(c(-0.1, 51.5), precision = 2)   # 0.1-minute

# Multiple points
pts <- cbind(lon = c(-74, 139.7, 0), lat = c(40.7, 35.7, 51.5))
georef_fwd(pts)

# Reverse conversion
georef_rev(c("GJPJ3217", "SKNA2342", "FJBL0630"))