formatqgisrraster
How to open .grd raster layers in QGIS (or any other GIS)?
I have looked through previous questions, but not found any answer. My raster layers are outputs from running bfastSpatial in R and I can't seem to open them in QGIS. I have also been unsuccessful in converting the format to .tif so I am hoping there is some other option.
R is pretty good at spatial processing, but its not a replacement carto tool (yet). Its graphics have always been implicitly geared to small, simple images and diagrams suitable for journal articles and the like.
You can still do some neat things with packages like ggplot2 (perhaps with some extensions like ggmap and ggspatial), tmap, and mapview, but not with enormous datasets, and display options are both limited and incredibly fiddly compared to QGIS or Arc. Stick to QGIS if you want something really pretty.
That said, here's something I managed with ggplot and a couple of addons:
edit: source code for the above:
library(sp)
library(sf)
library(raster)
library(rosm)
library(ggspatial)
library(ggsn)
# my input raster is huge, I only want to plot a little bit
# mapsheets vector file obtained from qldspatial.information.qld.gov.au
BB <- st_read(file.path(boxdir, 'TV_mapsheets.gpkg'), quiet = TRUE)
tv <- BB[c(BB$DESCRIPTIO %in% 'TOWNSVILLE'), ]
little_clipper <- extent(matrix(st_bbox(tv), ncol = 2))
# crop raster to plot area (Crop is still ~200k cells)
dem <- raster(file.path(dest_dir, 'TV_DEM_S.tif'))
TV_dem <- crop(dem,
alignExtent(little_clipper, dem, snap = 'in'),
snap = 'in')
rm(dem)
# for granular control over plot extent and elements
tv_xmin <- extent(TV_dem)[1]
tv_xmax <- extent(TV_dem)[2]
tv_ymin <- extent(TV_dem)[3]
tv_ymax <- extent(TV_dem)[4]
ggosm(x = extent(tv_xmin, tv_xmax + 0.0275, tv_ymin, tv_ymax),
type = 'cartolight') +
geom_spatial(TV_dem, aes(fill = band1), alpha = 0.5) +
# C:\OSGeo4W64\apps\qgis-ltr\resources\cpt-city-qgis-min\bhw\bhw2\bhw2_39.svg:
scale_fill_gradientn(colours=c('#28dce2', '#8f5dd5', '#8f5dd5' ,'#ffff80',
'#f4893a', '#994469', '#581389' ),
values = c(0.0000, 0.1299, 0.2600, 0.4800,
0.5901, 0.7900, 1.000)) +
ggsn::north(x.min = tv_xmin, x.max = tv_xmax + 0.0235,
y.min = tv_ymin, y.max = tv_ymin - 0.001,
symbol = 7, scale = 0.08) +
ggsn::scalebar(x.min = tv_xmin, x.max = tv_xmax,
y.min = tv_ymin, y.max = tv_ymax,
anchor = c(x = tv_xmax + 0.025, y = tv_ymin),
height = 0.015, dist = 1, st.size = 3,
dd2km = TRUE, model = 'WGS84') +
ggtitle('SRTM DEM-S Elevation', subtitle = 'Townsville 1:25,000 topographic key map sheet') +
labs(x = 'Longitude', y = 'Latitude', fill = 'Elevation (m)') +
guides(fill = guide_colorbar(override.aes = list(alpha = 0.5))) +
theme(legend.position = c(0.9, 0.5),
legend.background = element_rect(fill = alpha('white', 0)),
legend.key.height = unit(0.7, "in")) +
coord_fixed()
I'd still like the legend to reflect the alpha value of the plot body, and I'd like a better way to ensure it scales properly in an *.rmd document, but haven't found good solutions for that yet.
Best Answer
There is no gdal driver for the native format of the raster package (gri + grd), that is why you cannot directly open it in QGIS. One workaround to open data in QGIS without duplicating them is to create an additional header file using the
hdr()function of the raster package.Point to the
.grifile when opening with QGIS