Skip to content
Snippets Groups Projects
Commit 07168b81 authored by Genova, Giulio's avatar Genova, Giulio
Browse files

Merge branch 'wcsfromr' into 'master'

changed tutorial markdown/webdav_from_R.md

See merge request !1
parents fabb1154 1e868797
Branches
No related tags found
1 merge request!1changed tutorial markdown/webdav_from_R.md
......@@ -4,14 +4,13 @@
# [WebDAV](https://files.isric.org/soilgrids/data/recent/): direct access to the maps in VRT format.
### R
**This code is tested for GDAL version 2.4.x. When running with GDAL version 3.x.x there may be problems. We are working on providing updates**
#### Load libraries, select boundary box and cell size
Initially you need to load the following libraries and select the bounding box of the area you are interested in:
```R
library(rgdal)
library(gdalUtils)
```{r}
library(terra)
library(gdalUtilities)
bb=c(-337500.000,1242500.000,152500.000,527500.000) # Example bounding box (homolosine) for Ghana
igh='+proj=igh +lat_0=0 +lon_0=0 +datum=WGS84 +units=m +no_defs' # proj string for Homolosine projection
......@@ -21,13 +20,12 @@ sg_url="/vsicurl?max_retry=3&retry_delay=1&list_dir=no&url=https://files.isric.o
#### To a geotiff in Homolosine
This GDAL command will create a local geotiff in the Homolosine projection
```R
```{r}
gdal_translate(paste0(sg_url,'ocs/ocs_0-30cm_mean.vrt'),
"./crop_roi_igh_r.tif",
tr=c(250,250),
projwin=bb,
projwin_srs =igh,
verbose=TRUE)
projwin_srs =igh)
```
#### To a geotiff in a different projection
......@@ -36,30 +34,30 @@ The following commands describe a workflow to obtain a VRT or a GeoTiff for an a
##### To local VRT in homolosine (directly from the webdav connection)
The first step is to obtain a VRT for the area of interest in the Homolosine projection. We suggest to use VRT for the intermediate steps to save space and computation times.
```R
```{r}
gdal_translate(paste0(sg_url,'ocs/ocs_0-30cm_mean.vrt'),
"./crop_roi_igh_r.vrt",
of="VRT",tr=c(250,250),
projwin=bb,
projwin_srs =igh,
verbose=TRUE)
projwin_srs =igh)
```
##### To a VRT in, for example, LatLong
The following command will generate a VRT in the projection of your choice:
```R
```{r}
gdalwarp("./crop_roi_igh_r.vrt",
"./crop_roi_ll_r.vrt",
s_src=igh,
s_srs=igh,
t_srs="EPSG:4326",
of="VRT")
of="VRT",
overwrite = TRUE)
```
##### To a final Geotiff
The following command will generate a Geotiff in the projection of your choice for the area of interest defined above
```R
```{r}
gdal_translate("./crop_roi_ll_r.vrt",
"./crop_roi_ll_r.tif",
co=c("TILED=YES","COMPRESS=DEFLATE","PREDICTOR=2","BIGTIFF=YES"))
......@@ -68,14 +66,18 @@ gdal_translate("./crop_roi_ll_r.vrt",
#### Read in R
Finally you can read any of the generated VRTs or GeoTiffs in R for further analysis
```R
r=readGDAL("./crop_roi_igh_r.vrt") # Or any other of the files produce above
```{r}
rst=rast("./crop_roi_igh_r.vrt") # Or any other of the files produce above
```
```{r}
plot(rst) # Plot the file
```
# To download a global geotiff in Homolosine projection
```R
```{r}
gdal_translate(paste0(sg_url,'ocs/ocs_0-30cm_mean.vrt'),
"./crop_roi_igh_r.tif",
verbose=TRUE)
"./crop_roi_igh_r.tif")
```
0% Loading or .
You are about to add 0 people to the discussion. Proceed with caution.
Please register or to comment