LLtoTM: Convert Lat and Long to Transverse Mercator (TM)

In sptotal: Predicting Totals and Weighted Sums from Spatial Data

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]

sptotal documentation built on Dec. 12, 2022, 1:06 a.m.