topography

The goal of topography is to provide configurations to some big player topography sources. These are intended for use directly via GDAL (see for example gdalio) but we only really need text processing stuff here, no actual spatial stuff.

Installation

You can install the development version from GitHub with:

remotes::install_github("hypertidy/topography")
#options(repos = c(
#    hypertidy = 'https://hypertidy.r-universe.dev',
#    CRAN = 'https://cloud.r-project.org'))
#install.packages("topography")

Example

This is a basic example showing a few sources and read via GDAL into matching grids.

library(gdalio)
source(system.file("raster_format/raster_format.codeR", package = "gdalio", mustWork = TRUE))
## read as matrix
# gdalio_matrix <- function(dsn, ...) {
#   v <- gdalio_data(dsn, ...)
#   g <- gdalio_get_default_grid()
#   matrix(v[[1]], g$dimension[1])[,g$dimension[2]:1, drop = FALSE]
# }
## plot the data
gdalio_plot <- function(x, col = grey.colors(256), ..., asp = 1,  useRaster = TRUE) {
  g <- gdalio_get_default_grid()
  image(list(x = seq(g$extent[1], g$extent[2], length.out = g$dimension[1] + 1),
             y = seq(g$extent[3], g$extent[4], length.out = g$dimension[2] + 1),
             z = x), col = col, ..., useRaster = useRaster, asp = asp)
}

## set default grid to use as target
gdalio_set_default_grid(list(extent = c(50, 180, -85, -20),
 dimension = as.integer(c(1024, 512)),
 projection = "OGC:CRS84"))

## package to configure some transparent online topography sources
library(topography)

gebco <- gdalio_matrix(topography_source(x = "gebco"))
gdalio_plot(gebco, main = "GEBCO", asp = 1.6)

## for SRTM we want much smaller regions WIP

ll <- cbind(55.7558, 37.6173)[,2:1, drop = FALSE]
g <- list(extent = c(-1, 1, -1, 1) * 9000, dimension = c(512, 512), projection = sprintf("+proj=laea +lon_0=%f +lat_0=%f", ll[1], ll[2]))
gdalio_set_default_grid(g)
srtm <- gdalio_matrix(topography_source(x = "srtm_gl1"))
gdalio_plot(srtm, main = "srtm_gl1 30m", asp = 1.6)

gdalio_raster(topography_source(x = "srtm_gl1"))
#> Warning: multiple methods tables found for 'approxNA'

#> class      : RasterLayer 
#> dimensions : 512, 512, 262144  (nrow, ncol, ncell)
#> resolution : 35.15625, 35.15625  (x, y)
#> extent     : -9000, 9000, -9000, 9000  (xmin, xmax, ymin, ymax)
#> crs        : +proj=laea +lat_0=55.7558 +lon_0=37.6173 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
#> source     : memory
#> names      : layer 
#> values     : 100, 223  (min, max)

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Code of Conduct

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