geographiclib (version 0.4.1)

mgrs_fwd: Convert coordinates to/from Military Grid Reference System (MGRS)

Description

Convert geographic coordinates (longitude/latitude) to MGRS grid reference strings, or convert MGRS strings back to coordinates.

Usage

mgrs_fwd(x, precision = 5L)
mgrs_rev(code)

Value

• mgrs_fwd(): Character vector of MGRS grid reference strings

• mgrs_rev(): Data frame with columns:

  • lon: Longitude in decimal degrees

  • lat: Latitude in decimal degrees

  • x: Easting in meters (UTM/UPS projection)

  • y: Northing in meters (UTM/UPS projection)

  • zone: UTM zone number (0 for polar UPS regions)

  • northp: Logical, TRUE for northern hemisphere, FALSE for southern

  • precision: Integer precision level (0-5) encoded in the MGRS string

  • convergence: Meridian convergence in degrees (angle between true north and grid north)

  • scale: Scale factor at the point (dimensionless, typically near 1.0)

  • grid_zone: Grid zone designator (e.g., "51P", "04L")

  • square_100km: 100km square identifier (e.g., "SM", "GH")

  • crs: EPSG code string for the appropriate UTM/UPS projection (e.g., "EPSG:32755" for UTM zone 55S, "EPSG:32661" for UPS North)

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 between 0 and 5 (default 5) specifying the precision of the MGRS grid reference:

• 0: 100 km precision

• 1: 10 km precision

• 2: 1 km precision

• 3: 100 m precision

• 4: 10 m precision

• 5: 1 m precision (full precision)

Can be a vector to specify different precisions for each point.

code

Character vector of MGRS grid reference strings to convert back to coordinates.

Details

The Military Grid Reference System (MGRS) is a geocoordinate standard used by NATO militaries for locating points on Earth. It is an alternative to latitude/longitude that uses a hierarchical grid system.

Both functions are fully vectorized. Missing values (NA) are not currently supported.

For polar regions (latitude > 84°N or < 80°S), the Universal Polar Stereographic (UPS) system is used instead of UTM, indicated by zone = 0.

Examples

# Single point conversion
(code <- mgrs_fwd(cbind(147.325, -42.881)))
mgrs_rev(code)

# Multiple points with varying precision
x <- cbind(lon = c(-63.22, 34.02, 49.45, 45.67, 47.4),
           lat = c(17.62, -1.9, 37.47, 39.84, 33.15))
codes <- mgrs_fwd(x, precision = c(5, 4, 3, 2, 1))
codes

# Reverse conversion returns detailed coordinate information
result <- mgrs_rev(codes)
result

# Polar regions use UPS (zone 0)
polar_codes <- mgrs_fwd(cbind(c(147, -100), c(88, -88)))
mgrs_rev(polar_codes)