Horizontal / vertical grid cells distortion

[elgabbas]

Hello,

I am plotting multiple projected [EPSG:3035] spatraster objects, all having the same extent. ExampleMap.zip

However, the mapped grid cells are distorted, either horizontally or vertically (i.e. not square), or shown larger than they should be.

# vertically distorted  
    (ggplot2::ggplot() +
      tidyterra::geom_spatraster(data = terra::rast(ExampleMap[[1]])) +
      paletteer::scale_fill_paletteer_c(na.value = NA, "viridis::plasma")) %>%   
      ggplot2::ggsave(filename = "ExampleMap1.jpeg", width = 25, height = 20, units = "cm", dpi = 600)

# horizontally distorted  
      (ggplot2::ggplot() +
      tidyterra::geom_spatraster(data = terra::rast(ExampleMap[[2]])) +
      paletteer::scale_fill_paletteer_c(na.value = NA, "viridis::plasma")) %>% 
      ggplot2::ggsave(filename = "ExampleMap2.jpeg", width = 25, height = 20, units = "cm", dpi = 600)

    # This seems to be okay
     (ggplot2::ggplot() +
      tidyterra::geom_spatraster(data = terra::rast(ExampleMap[[3]])) +
      paletteer::scale_fill_paletteer_c(na.value = NA, "viridis::plasma")) %>% 
      ggplot2::ggsave(filename = "ExampleMap3.jpeg", width = 25, height = 20, units = "cm", dpi = 600)

Is it possible to ensure that the plotted maps do not show this distortion (i.e., always shown as a rectangle).

Thanks

[dieghernan]

See tidyverse/ggplot2#5523 and tidyverse/ggplot2#3025 (also https://stackoverflow.com/questions/77474839/ggplot-of-raster-maps-horizontal-vertical-grid-cells-distortion/77486091#77486091).

It seems that it more a plotting issue (rather than distorting) related with how geom_raster() handles NA when the number of non-NA cells is low. Instead, use transparent:

# Get the data

tmp <- "ExampleMap.zip"
download.file(
  "https://github.com/dieghernan/tidyterra/files/13322139/ExampleMap.zip",
  tmp
  
)
dataset <- unzip(tmp, list = TRUE)[1]
unzip(tmp)


load("ExampleMap.RData")

library(terra)
#> terra 1.7.55
library(raster) # For the reprex
#> Loading required package: sp
library(tidyterra)
#> 
#> Attaching package: 'tidyterra'
#> The following object is masked from 'package:raster':
#> 
#>     select
#> The following object is masked from 'package:stats':
#> 
#>     filter
library(ggplot2)
library(paletteer)

ExampleMap1 <- rast(ExampleMap[[1]])


# Reproduce

ggplot() +
  geom_spatraster(data = ExampleMap1, maxcell = Inf) +
  paletteer::scale_fill_paletteer_c(na.value = NA, "viridis::plasma")

# Use transparent
ggplot() +
  geom_spatraster(data = ExampleMap1, maxcell = Inf) +
  paletteer::scale_fill_paletteer_c(na.value = "transparent", "viridis::plasma")

^{Created on 2023-11-15 with reprex v2.0.2}

I would let this issue open until I documented this situation and also include it on the FAQs

[elgabbas]

Thanks Diego.. This solves the issue with the provided example. I will implement it on other maps. Cheers.

[dieghernan]

Closed after #122