CODEWITHSUNDEEP
rplotmapping
Shannon Murphy
Shannon Murphy

Reputation: 71

How to plot a bathymetry map in r with few colors and contours?

I trying to create a bathymetry map of Papua New Guinea in R, but when I plot the map, it looks very busy with all the contour. I want to just make the land one color, and the water a second color, so the map looks very simple. I have attached my r code and the map created when I use it.

Best, Shannon

library(marmap)
PNG_Map <- getNOAA.bathy(lon1 = 144, lon2 = 158, lat1 = -14, lat2 = -8, 
resolution = 1) 
summary(PNG_Map)
library(zoom)

white <- ("white")
black <- ("black")

par(mfrow=c(1,1))

plot(PNG_Map, image = TRUE, land = TRUE, xlim=c(148.75,154), 
ylim=c(-14, -8.75), xaxs = "i", yaxs = "i", lty = c(1, 1, 1), lwd = 
c(0.6, 0.6, 1.2), bpal = list(c(0, max(PNG_Map), black), 
c(min(PNG_Map),0 , white)))

Map of PNG

Upvotes: 2

Views: 1530

Answers (2)

Benoit
Benoit

Reputation: 1234

I strongly advise you to create your map by calling the plot.bathy() function several times to draw what you want element by element. That way, you can add as many or as few isobaths as you want. Here are two examples based on your code (I've deleted unnecessary lines and arguments):

library(marmap)
PNG_Map <- getNOAA.bathy(lon1 = 144, lon2 = 158, lat1 = -14, lat2 = -8, resolution = 1)     

# --- Black and white ---
plot(PNG_Map, image = TRUE, land = TRUE, xlim=c(148.75,154), ylim=c(-14, -8.75), n=100, lwd = 0.03, bpal = list(c(0, max(PNG_Map), grey(.3)), c(min(PNG_Map),0 , "white")))
plot(PNG_Map, deep=0, shallow=0, lwd = 0.6, add=T)  # Add coastline
plot(PNG_Map, deep=-200, shallow=-200, lwd = 0.4, drawlabels=T, add=T)  # Add -200m isobath
plot(PNG_Map, deep=-2000, shallow=-2000, lwd = 0.4, drawlabels=T, add=T)  # Add -2000m isobath


# --- With colors ---
# Creating color palettes
blues <- c("lightsteelblue4", "lightsteelblue3", "lightsteelblue2", "lightsteelblue1")
greys <- c(grey(0.6), grey(0.93), grey(0.99))

plot(PNG_Map, image = TRUE, land = TRUE, xlim=c(148.75,154), ylim=c(-14, -8.75), lwd = 0.03, bpal = list(c(0, max(PNG_Map), greys), c(min(PNG_Map),0 , blues)))
plot(PNG_Map, deep=0, shallow=0, lwd = 1, add=T)  # Add coastline
plot(PNG_Map, deep=-200, shallow=-200, lwd = 0.4, drawlabels=T, add=T)  # Add -200m isobath
plot(PNG_Map, deep=-2000, shallow=-2000, lwd = 0.4, drawlabels=T, add=T)  # Add -2000m isobath

enter image description here enter image description here

The key arguments to play with when calling plot.bathy() for the first time are:

  • n=: specifies a rough number of isobaths to plot
  • lwd=: specifies the width of isobath lines

As suggested by lukeA, check ?plot.bathy but also vignette("marmap") and vignette("marmap-DataAnalysis"). A whole lot of examples are presented there.

Upvotes: 1

lukeA
lukeA

Reputation: 54237

I guess you could try it like this:

pal1 <- list(
  c(min(PNG_Map), 0, "purple", "blue", "lightblue"),
  c(0, max(PNG_Map), "yellow", "brown"))
pal2 <- list(
  c(min(PNG_Map), 0, "blue"),
  c(0, max(PNG_Map), "yellow"))
plot_it <- function(pal, n, ...) {
  plot(PNG_Map, image=TRUE, land = TRUE, bpal = pal, n = n,
       xlim=c(148.75,154), ylim=c(-14, -8.75), ...)
}
par(mfrow = c(3, 1), mar = c(0,0,0,0), bty="n", xaxt="n", yaxt="n")
plot_it(pal1, 1)
plot_it(pal2, 10)
plot_it(pal2, 10, deep=min(PNG_Map), shallow=0, step = 1000)

enter image description here

Also check ?plot.bathy for the documentation.

Upvotes: 0

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