[R-sig-Geo] aligning tick maks with coord_map and ggplot

[Andy Bunn]

Hi all, given the map below is there an easy way to align the tick marks and text with the graticule? Many thanks, Andy

p1 <- ggplot() + borders("world", colour="gray50", fill="gray50")
p1 <- p1 + coord_map("ortho", orientation = c(40, -110, 0),
                     xlim=c(-133,-96),ylim=c(17,54))
p1