From 4476a381ff7150fa7d2ad8fcd5d3eb6f39dd47ae Mon Sep 17 00:00:00 2001
From: Robin Lovelace <rob00x@gmail.com>
Date: Fri, 3 Sep 2021 23:38:18 +0100
Subject: [PATCH] Reproject result of elevation_get() for #37

---
 R/slope_get.R        | 22 ++++++++++++++--------
 man/elevation_get.Rd |  6 +++++-
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/R/slope_get.R b/R/slope_get.R
index c17f00c..54f0213 100644
--- a/R/slope_get.R
+++ b/R/slope_get.R
@@ -15,6 +15,8 @@
 #' [README](https://github.com/hypertidy/ceramic#local-caching-of-tiles).
 #'
 #' @param ... Options passed to `cc_elevation()`
+#' @param output_format What format to return the data in?
+#'   Accepts `"raster"` (the default) and `"terra"`.
 #' @inheritParams slope_raster
 #' @return A raster object with cell values representing elevations in the
 #'   bounding box of the input `routes` object.
@@ -27,11 +29,12 @@
 #' routes = cyclestreets_route
 #' e = elevation_get(routes)
 #' class(e)
+#' crs(e)
 #' e
 #' plot(e)
 #' plot(st_geometry(routes), add = TRUE)
 #' }
-elevation_get = function(routes, ...) {
+elevation_get = function(routes, ..., output_format = "raster") {
   if(requireNamespace("ceramic")) {
     mid_ext = sf_mid_ext_lonlat(routes)
     bw = max(c(mid_ext$width, mid_ext$height)) / 1 # buffer width
@@ -41,13 +44,16 @@ elevation_get = function(routes, ...) {
   } else {
     message("Install the package ceramic")
   }
-  # issue: cannot convert CRS currently
-  # cr = sf::st_crs(routes)
-  # cr$wkt
-  # raster::crs(e) = raster::crs("+init=epsg:3857")
-  # raster::projectRaster(e, "+init=epsg:4326")
-  # raster::projectRaster(e, sf::st_crs(routes)[[2]])
-  e
+  crs_routes = sf::st_crs(routes)
+  if(!requireNamespace("terra", quietly = TRUE)) {
+    message('install.packages("terra") # for this to work')
+  }
+  et = terra::rast(e)
+  res = terra::project(et, y = crs_routes$wkt)
+  if(output_format == "raster") {
+    res = raster::raster(res)
+  }
+  res
 }
 
 sf_mid_ext_lonlat = function(routes) {
diff --git a/man/elevation_get.Rd b/man/elevation_get.Rd
index ae6852b..497630b 100644
--- a/man/elevation_get.Rd
+++ b/man/elevation_get.Rd
@@ -4,13 +4,16 @@
 \alias{elevation_get}
 \title{Get elevation data from hosted maptile services}
 \usage{
-elevation_get(routes, ...)
+elevation_get(routes, ..., output_format = "raster")
 }
 \arguments{
 \item{routes}{Routes, the gradients of which are to be calculated.
 The object must be of class \code{sf} with \code{LINESTRING} geometries.}
 
 \item{...}{Options passed to \code{cc_elevation()}}
+
+\item{output_format}{What format to return the data in?
+Accepts \code{"raster"} (the default) and \code{"terra"}.}
 }
 \value{
 A raster object with cell values representing elevations in the
@@ -39,6 +42,7 @@ library(raster)
 routes = cyclestreets_route
 e = elevation_get(routes)
 class(e)
+crs(e)
 e
 plot(e)
 plot(st_geometry(routes), add = TRUE)