R/HK1980GRID_TO_WGS84UTM.R

In helixcn/HK80: Conversion Tools for HK80 Geographical Coordinate System

#' Convert HK1980GRID coordinates to WGS84UTM coordinates
#' 
#' Convert HK1980GRID coordinates to WGS84UTM coordinates
#' 
#' This function converts the HK1980GRID coordinates to HK80 geographical
#' coordinates (latitude and longitude ) first, and then converts the later to
#' HK80UTM coordinates, and eventually converts the HK80UTM coordinates to
#' WGS84UTM.
#' 
#' @param N Numeric, Northern coordinate in meters
#' @param E Numeric, Eastern coordinate in meters
#' @return \item{N}{Northern coordinate in meters} \item{E}{Eastern coordinate
#' in meters} \item{zone}{Zone}
#' @note The coordinates should be within the range of Hong Kong. Providing
#' coordinates outside Hong Kong will lead to wrong results.
#' @author Jinlong Zhang
#' @seealso \code{\link{WGS84UTM_TO_HK1980GRID}}
#' @references Survey & Mapping Office Lands Department, Hong Kong Government
#' (1995).  Explanatory Notes on Geodetic Datums in Hong Kong, available at:
#' \url{http://www.geodetic.gov.hk/smo/gsi/data/pdf/explanatorynotes.pdf}
#' @keywords HK1980GRID WGS84UTM
#' @examples
#' 
#' options(digits = 15)
#' HK1980GRID_TO_WGS84UTM(820351.389, 832591.320)
#' 
#' #### $N
#' #### [1] 2471278.72371238
#' #### 
#' #### $E
#' #### [1] 205493.220852789
#' #### 
#' #### $zone
#' #### [1] 50
#' 
#' ######################################
#' #### Answer from the online Conversion tool
#' #### http://www.geodetic.gov.hk/smo/tform/tform.aspx
#' #### 50Q 	2471279 	205494
#' 
#' 
#' @export HK1980GRID_TO_WGS84UTM
HK1980GRID_TO_WGS84UTM <-
  function(N, E) {
    #### The unit for N and E is meter
    temp <- HK1980GRID_TO_HK80GEO(N, E)
    temp2 <- HK80GEO_TO_HK80UTM(temp$latitude, temp$longitude)
    res <- HK80UTM_TO_WGS84UTM(temp2$N, temp2$E, zone = temp2$zone)
    return(res)
  }