utmups_fwd: Convert coordinates to/from UTM/UPS projection

In geographiclib: Access to 'GeographicLib'

Convert coordinates to/from UTM/UPS projection

Description

Convert geographic coordinates (longitude/latitude) to UTM or UPS projected coordinates, or convert projected coordinates back to geographic coordinates.

Usage

utmups_fwd(x)

utmups_rev(easting, northing, zone, northp)

Arguments

x	A two-column matrix or data frame of coordinates (longitude, latitude) in decimal degrees for forward conversion, or a list with longitude and latitude components. Can also be a length-2 numeric vector for a single point.
easting	Numeric vector of easting values (x coordinates) in meters for reverse conversion.
northing	Numeric vector of northing values (y coordinates) in meters for reverse conversion.
zone	Integer vector of UTM zone numbers (1-60) or 0 for UPS (polar regions).
northp	Logical vector indicating hemisphere: TRUE for northern hemisphere, FALSE for southern hemisphere.

Details

The Universal Transverse Mercator (UTM) system divides the Earth into 60 zones, each 6 degrees of longitude wide. For polar regions (latitude > 84°N or < 80°S), the Universal Polar Stereographic (UPS) system is used instead, indicated by zone = 0.

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

The convergence angle represents the angle between true north and grid north at a point. The scale factor represents the ratio of the scale along a line to the scale on the reference surface (typically very close to 1.0).

Value

• utmups_fwd(): Data frame with columns:

  • x: Easting in meters

  • y: Northing in meters

  • zone: UTM zone number (1-60) or 0 for UPS

  • northp: Logical, TRUE for northern hemisphere

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

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

  • lon: Longitude in decimal degrees (echoed from input)

  • lat: Latitude in decimal degrees (echoed from input)

  • crs: EPSG code string for the UTM/UPS projection

• utmups_rev(): Data frame with columns:

  • lon: Longitude in decimal degrees

  • lat: Latitude in decimal degrees

  • x: Easting in meters (echoed from input)

  • y: Northing in meters (echoed from input)

  • zone: UTM zone number (echoed from input)

  • northp: Hemisphere indicator (echoed from input)

  • convergence: Meridian convergence in degrees

  • scale: Scale factor at the point

  • crs: EPSG code string for the UTM/UPS projection

Examples

# Single point forward conversion
result <- utmups_fwd(c(147.325, -42.881))
result

# Multiple points
pts <- cbind(lon = c(147, 148, -100, 0),
             lat = c(-42, -43, -42, 0))
utmups_fwd(pts)

# Reverse conversion
utmups_rev(result$x, result$y, result$zone, result$northp)

# Round-trip conversion
fwd <- utmups_fwd(pts)
rev <- utmups_rev(fwd$x, fwd$y, fwd$zone, fwd$northp)
cbind(original = pts, converted = rev[, c("lon", "lat")])

# Polar regions use UPS (zone 0)
polar <- cbind(c(147, 148, -100), c(88, -88, -85))
utmups_fwd(polar)

geographiclib documentation built on March 4, 2026, 9:07 a.m.