LLtoTM {sptotal} | R Documentation |
Convert Lat and Long to Transverse Mercator (TM)
Description
Latitude and Longitude coordinates are converted to TM projection coordinates with a user-defined central meridian. The resulting units from applying the function are kilometers.
Usage
LLtoTM(cm, lat, lon, xcol = "x", ycol = "y", minx = NULL, miny = NULL)
Arguments
cm |
is the user defined central median. A common choice is the mean of the longitude values in your data set |
lat |
is the vector of latitudes |
lon |
is the vector of longitudes |
xcol |
is the name of the output TM column of x coordinates |
ycol |
is the name of the output TM column of y coordinates |
minx |
is 'NULL' by default and sets the minimum x-coordinate value to 0. This is an optional minimum value for the x-coordinate vector. |
miny |
is 'NULL' by default and sets the minimum y-coordinate value to 0. This is an optional minimum value for the y-coordinate vector. |
Details
This function only should only be used if the coordinates supplied by the user are latitude and longitude. The default TM projection here specifies that both the minimum x and y-coordinate values are 0 scaled to 1 km.
Value
A list with the TM coordinates as the first component of the list. The first component of the list contains x coordinates in the first column and y coordinates in the second column. The remaining elements of the list are the cm
, minx
, and miny
values that were input.
Examples
## Add transverse Mercator x and y coordinates to a data frame with
## latitude/longitude coordinates. Name these \code{xc_TM_} and \code{yc_TM_}.
exampledataset$xc_TM_ <- LLtoTM(cm = base::mean(exampledataset[ ,"xcoords"]),
lat = exampledataset[ ,"ycoords"],
lon = exampledataset[ ,"xcoords"])$xy[ ,1]
exampledataset$yc_TM_ <- LLtoTM(cm = base::mean(exampledataset[ ,"xcoords"]),
lat = exampledataset[ ,"ycoords"],
lon = exampledataset[ ,"xcoords"])$xy[ ,2]