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seaice.map

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The goal of seaice.map is to

• download very latest available sea ice concentration data
• generate a global map of the data with a customizable focus (i.e. global but centred on Tasmania/East Antarctica)
• also show some contextual spatio-temporal data (i.e. recent movements of a research vessel)
• explicate how to do this all with free tools.

First, a modified map of the subsequent one to put the ship in the centre. (we’ll fix this up)

#> [1] "2021-12-23 05:00:00 UTC" "2025-11-11 12:11:00 UTC"
#> terra 1.8.80

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Now the map we carefully designed (but keep changing to figure out how we’d like to think about East Antarctica).

library(terra)
r <- vapour::gdal_raster_data("data-raw/seaice.png", bands = 1:3)
pcrs <- attr(r, "projection")
ximage::ximage(r, asp = 1, axes = FALSE)
points(terra::project(do.call(cbind, maps::map(plot = F)[1:2]), to = pcrs, from = "OGC:CRS84"), pch = ".", col = "#777777")
title(readLines("data-raw/latestseaicefile.txt")[1], line = -2, col.main = "hotpink")

ptrack <- terra::project(as.matrix(track), to = pcrs, from = "OGC:CRS84")

lines(ptrack, col = "hotpink")
pt <- tail(ptrack[!is.na(track[,1]) & !is.na(ptrack[,2]), ], 1L)

n <- 30 * 24 * 60

dat <- nuyina_underway()


dat$longitude[dat$longitude < 0] <- -dat$longitude[dat$longitude < 0] 
print(range( dat$datetime))
#> [1] "2021-12-23 05:00:00 UTC" "2025-11-11 12:12:00 UTC"
dat <- tibble::as_tibble(dat)
dat <- tail(dat, n)
dat$datetime <- as.POSIXct(dat$datetime, "%Y/%m/%d %H:%M:%S", tz = "UTC")

#track0 <- cbind(dat$longitude, dat$latitude)

#track <- terra::project(as.matrix(track0), to = pcrs, from = "OGC:CRS84")
lines(ptrack, col = "hotpink")
pt <- tail(ptrack[!is.na(ptrack[,1]) & !is.na(ptrack[,2]), ], 1L)
points(pt, pch = "+", col = "hotpink")
## key locations just defined in the source of this document
pl[c("X", "Y")] <- terra::project(cbind(pl$x, pl$y), to = pcrs, from = "OGC:CRS84")
points(pl$X, pl$Y, pch = 19, col = "hotpink", cex = 0.5)
bx <- c(range(ptrack[,1], na.rm = TRUE), range(ptrack[,2], na.rm = TRUE))
rect(bx[1], bx[3], bx[2], bx[4])
claims <- terra::project(terra::vect("data-raw/claims/claim_boundaries_ps.shp"), pcrs)

plot(claims, add = TRUE)

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map <- terra::vect("data-raw/CGAZ.fgb")



ptrack0 <- terra::project(as.matrix(track), to = pcrs0, from = pcrs)
plot(tail(ptrack0, 10000), type = "n", asp = 1, axes = F, xlab = "", ylab = "")
title(paste0(as.Date(range(dat$datetime)),collapse = ","), col.main = "white")
#plotRGB(r, add = TRUE)
ximage::ximage(r0, add = TRUE)
lines(tail(ptrack0, 4000), col = "hotpink")
plot(terra::project(map, pcrs0), add = TRUE, border = "#777777")

plot(terra::project(claims, pcrs0), add = TRUE)
pl[c("X", "Y")] <- terra::project(cbind(pl$x, pl$y), to = pcrs0, from = "OGC:CRS84")
points(pl$X, pl$Y, pch = 19, col = "hotpink", cex = 1)

pt_recent <- tail(ptrack0, 1000)
lines(pt_recent, lwd = 3, col = "green")
points(tail(pt_recent, 1), pch = "X", cex = 2, col = "white")

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rr <- diff(par("usr"))[c(1, 3)]
if (rr[1] > rr[2]) {
  dm <- as.integer(c(1, rr[2]/rr[1]) * 1024)
} else {
  dm <- as.integer(c(1, rr[1]/rr[2]) * 1024)
}
cont <- terra::project(terra::rast("/vsicurl/https://gebco2023.s3.valeria.science/gebco_2023_land_cog.tif"), 
               terra::rast(terra::ext(par("usr")), ncols = dm[1], nrows = dm[2], crs = pcrs0))
cont[cont > -10] <- NA
try(contour(cont, add = TRUE, col = "lightgrey", breaks = quantile(na.omit(values(cont)[,1]), seq(0.1, 1, by = 10))), silent = TRUE)

This is 25km sea ice concentration from NSIDC, reprojected from images published by NOAA at https://noaadata.apps.nsidc.org/NOAA/G02135/ (the projection is Transverse Mercator with central longitude 147).

The point (and track if available) is the recent position of the Nuyina research vessel taken from the underway data that measures atmospheric and water properties.

Files in ‘data-raw/’ contain the actual metadata and scripts. This runs as a daily task on github actions.

Now zoom in on the ship some more. This should just show coarse google imagery, with better Maxar imagery when near coastline.

loc <- ptrack[nrow(ptrack),,  drop = FALSE]
#loc <- pl[2, c("X", "Y")]
#loc <- terra::project(cbind(-70.933004,-10.7192677)[,2:1, drop = F], to = pcrs, from = "OGC:CRS84")
xr <- loc[1,1] + c(-1000, 1000) * 34
yr <- loc[1,2] + c(-1000, 1000)  * 34


goog <- sds::wms_googlehybrid_tms()
esri <- sds::wms_arcgis_mapserver_ESRI.WorldImagery_tms()
gmap <- vapour::gdal_raster_image(goog, target_ext = c(xr, yr), target_crs = pcrs, target_dim = c(1024, 0))
if (length(unique(gmap[[1]])) < 800) {

xr <- loc[1,1] + c(-1000, 1000) * 800
yr <- loc[1,2] + c(-1000, 1000) * 800
gmap <- vapour::gdal_raster_image(esri, target_ext = c(xr, yr), target_crs = pcrs, target_dim = c(1024, 0))
#length(unique(gmap[[1]]))
}


plot(loc[,1:2, drop = F], xlim = xr, ylim =yr, asp = 1, axes = FALSE, xlab = "", ylab = "")
ximage::ximage(gmap, add = T)
plot(claims, add = TRUE)

lines(ptrack, col = "hotpink")
points(pl$X, pl$Y, pch = 19, col = "hotpink", cex = 0.5)

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A sentinel-2-l2a image around the ship, or at least the last one that worked where the ship was at the time.

dat <- nuyina_underway()
print(range( dat$datetime))
#> [1] "2021-12-23 05:00:00 UTC" "2025-11-11 12:13:00 UTC"

track <- cbind(dat$longitude, dat$latitude)
## there's an artefact uploaded for each run, but we should probably put these elswhere ...WIP
r <- try(vapour::gdal_raster_data("data-raw/sentinel-image.tif", target_dim = c(1024, 0), bands = 1:3))

for (i in seq_along(r)) {
  r[[i]][is.na(r[[i]])] <- 0
}


if (!inherits(r, "try-error")) {
  ptrack <- terra::project(as.matrix(track), to = attr(r, "projection"), from = "OGC:CRS84")
for (i in 1:3) r[[i]][is.na(r[[i]])] <- 0
source("R/utils.R")
ximage::ximage(rescale_im(r), asp = 1)

lines(tail(ptrack, 5000), col = "hotpink")
points(tail(ptrack, 50), pch = 19, col = "hotpink", cex = 0.5)
}

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Now plot some of the underway data.

vars <- c("port_solar_irradiance", "shipnav_ground_course", "air_pressure_trend3h", "fore_2_wind_from_direction_true", "port_air_temperature", "longitude", "latitude")
which(vars %in% names(dat))
#> [1] 3 6 7
 for (i in seq_along(vars)) {
   bad <- is.na(dat[[vars[i]]])
   if (any(!bad)) {
     dat2 <- dat[!bad, ]
      plot(dat2$datetime, dat2[[vars[i]]], pch = 19, cex = .2, xlab = "", main = vars[i])
   }
 }

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Code of Conduct

Please note that the seaice.map project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.