I have a .tif file about the ground temperature of a certain region on Earth and I would like to find out the coordinates of the region.
Here is a link to the file I am working on: 2017001D.tif
Using raster package in R, I was able to load the .tif file as RasterLayer class.
I can extract the coordinate information as
> T001D = raster::raster("2017001D.tif")
> T001D
class : RasterLayer
dimensions : 4255, 5213, 22181315 (nrow, ncol, ncell)
resolution : 1000, 1000 (x, y)
extent : -2926932, 2286068, 1740497, 5995497 (xmin, xmax, ymin, ymax)
crs : NA
source : 2017001D.tif
names : X2017001D
> coords <- raster::xyFromCell(T001D, seq_len(ncell(T001D)))
> head(coords)
x y
[1,] -2926432 5994997
[2,] -2925432 5994997
[3,] -2924432 5994997
[4,] -2923432 5994997
[5,] -2922432 5994997
[6,] -2921432 5994997
I also used terra package to load it as SpatRaster class and when I do so I found more info:
> T001D = terra::rast("2017001D.tif")
> T001D
class : SpatRaster
dimensions : 4255, 5213, 1 (nrow, ncol, nlyr)
resolution : 1000, 1000 (x, y)
extent : -2926932, 2286068, 1740497, 5995497 (xmin, xmax, ymin, ymax)
coord. ref. : AEA_WGS_1984
source : 2017001D.tif
name : 2017001D
The coordinate system info seems to be AEA_WGS_1984. I looked for it online and found this post:How to convert WGS84 to Lat/Long using R which is similar to my question except I don't have a "zone" number.
It mentioned sp package and I feel like I need help with the functions in it now, such as the CRS syntax in spTransform() function. Can someone help me with this? Thank you
You can do
library(terra)
T001D <- rast("2017001D.tif")
coords <- crds(T001D, na.rm=FALSE)
geo_coords <- project(coords, crs(T001D), "+proj=longlat")
But why would you do that? You probably are approaching what you are after the wrong way. A more common approach (but necessarily what you should do either would be to use project
pT001D <- project(T001D, "+proj=longlat")
That can change the number of rows a bit and columns because it is a different raster geometry; although you can control that. See ?project