Barry Rowlingson wrote:
I receive GPS readings in a text string such as "0121.6723S 03643.6893E" and need the coordinates as decimal degrees in two separate variables: "-1.361205" and "36.728155". How do I do this in R?
- this works for the single test case you've given us:
Whoops, it doesn't. I'd forgotten that longitude degrees could be three digits (0-180) but latitude is only two (0-90). Fixed:
convertCoord <- function(coordString){
bits <- strsplit(coordString," ")
lat <- bits[[1]][1]
lon <- bits[[1]][2]
mdCon <- function(mdstring,nd){
d <- as.numeric(substr(mdstring,1,nd))
m <- as.numeric(substr(mdstring,nd+1,99))/60
return(d+m)
}
latD <- mdCon(substr(lat,1,nchar(lat)-1),2)
latSign <- ifelse(substr(lat,nchar(lat),nchar(lat))=="N",1,-1)
lonD <- mdCon(substr(lon,1,nchar(lon)-1),3)
lonSign <- ifelse(substr(lon,nchar(lon),nchar(lon))=="E",1,-1)
c(lonD*lonSign, latD*latSign)
} > convertCoord("0121.6723S 03643.6893E")
[1] 36.728155 -1.361205Note this isn't vectorised - if you feed it a vector of those coordinate strings, it wont do the right thing.
Baz
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