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R script to transform longitude to UTM zone and EPSG code for projections
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| # Functions to convert a longitude to the UTM zone and EPSG code | |
| # Get the UTM zone for a given longitude | |
| long2UTM <- function(long) {(floor((long + 180)/6) %% 60) + 1 } | |
| # get the EPSG code (int) for a given longitude and hemisphere | |
| UTMzone2EPSG <- function(utmzone, hemisphere) { | |
| if( tolower(hemisphere) %in% c("north", "n") ) { | |
| if( utmzone < 10 ) { epsg = '3260' } else { epsg = '326' } | |
| } else if( tolower(hemisphere) %in% c("south", "s") ) { | |
| if( utmzone < 10 ) { epsg = '3270' } else { epsg = '327' } | |
| } | |
| else { stop(paste0("hemisphere provided '", hemisphere, "' is not valid. Valid values are: north or south")) } | |
| return(as.integer(paste0(epsg, utmzone))) | |
| } | |
| # Tests | |
| # vancouver, CA | |
| long2UTM(-123) | |
| UTMzone2EPSG(long2UTM(-123), 'north') | |
| # melbourne, AU | |
| long2UTM(145) | |
| UTMzone2EPSG(long2UTM(145), 's') |
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