convUL function

Convert Coordinates between UTM and Lon/Lat

Convert coordinates between UTM and Lon/Lat.

convUL (xydata, km=TRUE, southern=NULL)

Arguments

• xydata: numeric -- data frame with columns X and Y.
• km: logical -- if TRUE, UTM coordinates within xydata are in kilometres; otherwise, metres.
• southern: logical -- if TRUE, forces conversions from UTM to longitude/latitude to produce coordinates within the southern hemisphere. For conversions from UTM, this argument defaults to FALSE. For conversions from LL, the function determines southern from xydata.

Details

The object xydata must possess a projection attribute that identifies the current projection. If the data frame contains UTM coordinates, it must also have a zone attribute equal to a number between 1 and 60 (inclusive). If it contains geographic (longitude/latitude) coordinates and the zone attribute is missing, the function computes the mean longitude and uses that value to determine the zone. The longitude range of zone $i$ is $-186 + 6i < x <= -180 + 6i degrees$.

This function converts the X and Y columns of xydata from "LL" to "UTM" or vice-versa. If the data span more than one zone to the right or left of the intended central zone, the underlying algorithm may produce erroneous results. This limitation means that the user should use the most central zone of the mapped region, or allow the function to determine the central zone when converting from geographic to UTM coordinates. After the conversion, this routine adjusts the data frame's attributes accordingly.

Returns

A data frame identical to xydata, except that the X and Y columns contain the results of the conversion, and the projection attribute matches the new projection.

References

Ordnance Survey. (2020) A guide to coordinate systems in Great Britain. Copyright Ordnance Survey 2018 (v3.6) . Southampton, UK.

Author(s)

Nicholas M. Boers, Software Engineer, Jobber, Edmonton AB

Maintainer: Rowan Haigh, Program Head -- Offshore Rockfish

Pacific Biological Station (PBS), Fisheries & Oceans Canada (DFO), Nanaimo BC

locus opus: Regional Headquarters, Vancouver BC

Last modified Rd: 2022-09-06

See Also

closePolys, fixBound.

Examples

local(envir=.PBSmapEnv,expr={
  oldpar = par(no.readonly=TRUE)
  #--- load the data
  data(nepacLL,envir=.PBSmapEnv)
  #--- set the zone attribute
  #--- use a zone that is most central to the mapped region
  attr(nepacLL, "zone") <- 6
  #--- convert and plot the result
  nepacUTM <- convUL(nepacLL)
  plotMap(nepacUTM)
  par(oldpar)
})