Generates a deterministic synthetic SpatRaster of ground-level PM2.5
(micrograms per cubic metre) covering Ontario. No raster source exists in
the Ontario GeoHub registry (every registered source is vector), so this
function provides a reproducible raster surface to exercise the package's
raster linking and mapping paths end-to-end.
Usage
retrieve_synthetic_raster(refresh = FALSE)
Arguments
- refresh
Logical. Accepted for signature uniformity with the other
retrieve_*() functions but unused: synthetic data is computed on demand
and needs no cache or network access. Defaults to FALSE.
Value
A single-layer SpatRaster (layer "pm25") in EPSG:4326 spanning
the Ontario bounding box, with source_name, source_url, and
retrieved_at R attributes attached for provenance. Note that terra
operations may drop these attributes; downstream code reads them through
an NA-safe fallback.
Details
Values are a pure, deterministic function of each cell's centroid
coordinates: a smooth north-to-south gradient (higher over the populated
south) plus two fixed Gaussian hotspots near Toronto and Ottawa. There is
no random component, so two calls return identical rasters.
Examples
# \donttest{
# first call bears the one-time terra/GDAL startup cost
r <- retrieve_synthetic_raster()
# }