read_GRTSmh***(): harden CRS representation *

Further follow-up to #67.

By using sp::CRS(SRS_string = "EPSG:31370"), compatibility is
offered:
- both for raster from CRAN and raster from GitHub
- both for PROJ4/GDAL2 and PROJ6+/GDAL3

To be revisited once raster from CRAN accepts simple EPSG-code
as input for crs<- (as on GitHub), i.e. with raster>=3.3-16

DESCRIPTION

@@ -49,7 +49,7 @@ Remotes:
     inbo/inborutils
 Encoding: UTF-8
 LazyData: true
-RoxygenNote: 7.1.0
+RoxygenNote: 7.1.1
 Suggests: 
     googledrive,
     knitr,
@@ -58,6 +58,7 @@ Suggests:
     readxl,
     remotes,
     rmarkdown,
+    sp,
     tidyverse,
     units
 VignetteBuilder: knitr

NAMESPACE

@@ -78,7 +78,6 @@ importFrom(rprojroot,is_rstudio_project)
 importFrom(sf,"st_crs<-")
 importFrom(sf,read_sf)
 importFrom(sf,st_centroid)
-importFrom(sf,st_crs)
 importFrom(sf,st_drop_geometry)
 importFrom(sf,st_transform)
 importFrom(stats,setNames)

R/GRTSmh.R

@@ -309,8 +309,6 @@ convert_base4frac_to_dec <-
 #' }
 #'
 #' @export
-#' @importFrom sf
-#' st_crs
 #' @importFrom raster
 #' raster
 #' brick
@@ -323,6 +321,12 @@ read_GRTSmh <-
                       "20_processed/GRTSmh_brick/GRTSmh_brick.tif"),
              brick = FALSE) {
 
+        if (!requireNamespace("sp", quietly = TRUE)) {
+            stop("Package \"sp\" is needed when using this function. ",
+                 "Please install it.",
+                 call. = FALSE)
+        }
+
         if (brick) {
             if (missing(file)) {
                     b <- brick(file.path(path, file[2]))} else {
@@ -337,7 +341,7 @@ read_GRTSmh <-
                    }
             result <- r
         }
-        crs(result) <- st_crs(31370)$proj4string
+        crs(result) <- sp::CRS(SRS_string = "EPSG:31370")
         return(result)
     }
 
@@ -427,16 +431,21 @@ read_GRTSmh <-
 #' }
 #'
 #' @export
-#' @importFrom sf
-#' st_crs
 #' @importFrom raster
 #' raster
 #' crs<-
 read_GRTSmh_base4frac <-
     function(path = fileman_up("n2khab_data"),
              file = "20_processed/GRTSmh_base4frac/GRTSmh_base4frac.tif") {
+
+        if (!requireNamespace("sp", quietly = TRUE)) {
+            stop("Package \"sp\" is needed when using this function. ",
+                 "Please install it.",
+                 call. = FALSE)
+        }
+
         r <- raster(file.path(path, file))
-        crs(r) <- st_crs(31370)$proj4string
+        crs(r) <- sp::CRS(SRS_string = "EPSG:31370")
         return(r)
     }
 
@@ -579,7 +588,6 @@ read_GRTSmh_base4frac <-
 #' @importFrom stringr str_c
 #' @importFrom sf
 #' read_sf
-#' st_crs
 #' st_crs<-
 #' @importFrom raster
 #' raster
@@ -608,11 +616,17 @@ read_GRTSmh_diffres <-
 
         } else {
 
+            if (!requireNamespace("sp", quietly = TRUE)) {
+                stop("Package \"sp\" is needed when using this function. ",
+                     "Please install it.",
+                     call. = FALSE)
+            }
+
             r <- raster(file.path(path, subdir,
                              str_c("GRTSmh_diffres.",
                                    level, ".tif")))
             names(r) <- str_c("level", level)
-            crs(r) <- st_crs(31370)$proj4string
+            crs(r) <- sp::CRS(SRS_string = "EPSG:31370")
             r
 
         }