Coordinate Conversion from UTM to Latitude and Longitude

Source: R/geography.R

generate_ll_from_utm() takes your dataframe with UTM coordinates in separate Easting and Northing columns, and adds on an additional two columns with the converted decimalLatitude and decimalLongitude coordinates using the reference coordinate system NAD83. Your data must also contain columns specifying the zone and datum of your UTM coordinates. In contrast to convert_utm_to_ll() (superseded), generate_ll_from_utm() requires zone and datum columns. It supports quoted or unquoted column names and a user-specified datum for lat/long coordinates. It also adds an extra column to the output data table that documents the lat/long coordinate reference system.

generate_ll_from_utm(
  df,
  EastingCol,
  NorthingCol,
  ZoneCol,
  DatumCol,
  latlong_datum = "NAD83"
)

Arguments

df

  • The dataframe with UTM coordinates you would like to convert. Input the name of your dataframe.

EastingCol

  • The name of your Easting UTM column. You may input the name with or without quotations, ie. EastingCol and "EastingCol" are both valid.

NorthingCol

  • The name of your Northing UTM column. You may input the name with or without quotations, ie. NorthingCol and "NorthingCol" are both valid.

ZoneCol

  • The column containing the UTM zone, with or without quotations.

DatumCol

  • The column containing the datum for your UTM coordinates, with or without quotations.

latlong_datum

  • The datum to use for lat/long coordinates. Defaults to NAD83.

Value

The function returns your dataframe, mutated with an additional two columns of decimalLongitude and decimalLatitude plus a column LatLong_CRS containing a PROJ string that specifies the coordinate reference system for these data.

Details

Define the name of your dataframe, the easting and northing columns within it, the UTM zone within which those coordinates are located, and the reference coordinate system (datum). UTM Northing and Easting columns must be in separate columns prior to running the function. If a datum for the lat/long output is not defined, the function will default to "NAD83". If there are missing coordinates in your dataframe they will be preserved, however they will be moved to the end of your dataframe. Note that some parameter names are not in snake_case but instead reflect DarwinCore naming conventions.

This function uses tidy evaluation (i.e. you can provide column name arguments as strings or you can leave them unquoted). If you wish to store column names as strings in variables, you must enclose the variables in double curly braces when you pass them into the function. See code examples below.

Examples

if (FALSE) { # \dontrun{

# Using magrittr pipe (%>%) and unquoted column names
my_dataframe %>%
generate_ll_from_utm(
  EastingCol = UTM_X,
  NorthingCol = UTM_Y,
  ZoneCol = Zone,
  DatumCol = Datum
)

# Providing column names as strings (in quotes)
generate_ll_from_utm(
  df = mydataframe,
  EastingCol = "EastingCoords",
  NorthingCol = "NorthingCoords",
  ZoneCol = "zone",
  DatumCol = "datum",
  latlong_datum = "WGS84"
)

# Column names stored as strings in separate variables
easting <- "EastingCoords"
northing <- "NorthingCoords"
zonecol <- "zone"
datumcol <- "datum"
latlong_dat <- "WGS84"

generate_ll_from_utm(
  df = mydataframe,
  EastingCol = {{easting}},  # enclose variables that store column names in {{}}
  NorthingCol = {{northing}},
  ZoneCol = {{zonecol}},
  DatumCol = {{datumcol}},
  latlong_datum = latlong_dat  # this isn't a column name so it doesn't need {{}}
)

} # }