I have a $5 Starbucks gift card that I simply can’t remember to use; I’ve had it since Christmas. So, I will mail it (within the U.S.A.) to the first commenter who can identify the longitude/latitude (within 5km) where two of these three vacation photos were taken (photos below). ***Update 3/30/2013: locations A and C have been identified***. Each location must be identified by longitude/latitude; names don’t count. Here are some short instructions for obtaining longitude/latitude values from Google Maps: 1 2. I know this is a stretch for R-bloggers, but I will be checking longitude/latitude entries using the following R code:

# convert degree, minute, second to decimal
dms2dec <- function(deg, min, sec) deg + (min + sec/60)/60
 
# convert degrees to radians
d2r <- function(d) d * pi / 180

# compute great circle distance (km) between two coordinates
# given in radians using the Haversine formula
hgcd <- function(lon1, lat1, lon2, lat2) {
    erth <- 6371 # average radius of earth (km)
    dlon <- (lon2 - lon1)
    dlat <- (lat2 - lat1)
    a <- sin(dlat/2)^2 + cos(lat1) * cos(lat2) * sin(dlon/2)^2
    c <- 2 * asin(min(1,sqrt(a)))
    erth * c
}

Location C (click to enlarge)

Location B (click to enlarge)

Location A (click to enlarge)