sf polygon layer from the processed data
source GRTSmh_diffresR/GRTSmh.R
read_GRTSmh_diffres.RdThe GRTSmh_diffres data source is derived from
GRTSmh_brick.
It provides the hierarchical levels 1 to 9 of the
GRTS cell addresses at the corresponding spatial resolution.
The function returns one selected level, either as a SpatRaster or as an
sf polygon layer (in the latter case, only levels 4 to 9 are
provided).
The coordinate reference system is 'BD72 / Belgian Lambert 72'
(EPSG-code 31370).
read_GRTSmh_diffres( dir = file.path(locate_n2khab_data(), "20_processed/GRTSmh_diffres"), level, polygon = FALSE )
| dir | The data source directory (absolute or relative).
The default follows the data management advice in the
vignette on data storage (run |
|---|---|
| level | Integer in the range from 1 to 9; determines the spatial resolution. See the Details section. |
| polygon | Logical; determines whether a polygon layer or a SpatRaster is returned. See the Details section. |
Either a SpatRaster or a Simple feature collection of geometry type
POLYGON.
If the package is configured to use the raster package
(see n2khab_options()), a RasterLayer is
returned instead of a SpatRaster.
The GRTSmh_diffres data source file is a file collection (available
at Zenodo), composed of
nine monolayered GeoTIFF files of the INT4S datatype plus a GeoPackage
with six polygon layers:
The polygon layers in the GeoPackage are the dissolved, polygonized
versions of levels 4 to 9 of the
GRTSmh_brick data source (see read_GRTSmh).
This means that they provide the decimal (i.e. base 10) integer values of
these higher hierarchical levels of the GRTS cell addresses
of the raw data source GRTSmaster_habitats.
Hence, the polygons are typically squares that correspond to the GRTS cell at
the specified hierarchical level.
The polygon layer is however restricted to the non-NA cells of the original
GRTSmaster_habitats raster.
Consequently, a part of the polygons is clipped along the Flemish border.
Levels 1 to 3 are not provided for the whole of Flanders,
because this would inflate the GPKG file.
You can look at the source code
to do such things.
The GeoTIFF files provide the respective levels 1 to 9 of the
GRTSmh_brick data source in a raster format, at the resolution that
corresponds to the GRTS cell at the specified hierarchical level.
The presence of NA cells around Flanders at level 0 implies that, with
decreasing resolution, the raster's extent increases and larger areas outside
Flanders are covered by non-NA cells along the border.
The function returns the selected level either as an sf polygon
layer or as a SpatRaster, depending on the
polygon argument.
The higher-level ranking numbers (compared to the original level 0) allow spatially balanced samples at lower spatial resolution than that of 32 m, and can also be used for aggregation purposes.
The levels 1 to 9 correspond to the resolutions vector
32 * 2^(1:9) in meters:
| level | resolution (m) |
| 1 | 64 |
| 2 | 128 |
| 3 | 256 |
| 4 | 512 |
| 5 | 1024 |
| 6 | 2048 |
| 7 | 4096 |
| 8 | 8192 |
| 9 | 16384 |
See R-code in the
n2khab-preprocessing repository for the creation from
the GRTSmh_brick data source.
Beware that not all GRTS ranking numbers at the specified level are provided, as the original GRTS raster has been clipped with the Flemish outer borders (i.e., not excluding the Brussels Capital Region).
Other functions involved in processing the 'GRTSmaster_habitats' data source:
convert_base4frac_to_dec(),
convert_dec_to_base4frac(),
read_GRTSmh(),
read_GRTSmh_base4frac()
if (FALSE) { # This example supposes that your working directory or a directory up to 10 # levels above has # the 'n2khab_data' folder AND that the latest version of the # 'GRTSmh_diffres' data source is present in the default subdirectory. # In all other cases, this example won't work but at least you can consider # what to do. r <- read_GRTSmh_diffres(level = 7) r p <- read_GRTSmh_diffres(level = 7, polygon = TRUE) p }