How a nearest-neighbour read of several sources is served.
dot-mosaic_read_spec.RdTiles no mosaic VRT can hold (south-up tiles, tiles in a neighbouring
projection, one Zarr array per UTM zone) stay a multi-path source. A
nearest-neighbour read of it takes each target cell from one source
pixel, a later source winning where it holds data, so the sources can
be read one at a time and laid over each window in order
(gdal_read_window_multi()): a direct window read where a source lies
on the target's pixels (.rio_direct_spec(), partial = TRUE), and
elsewhere an exact nearest-neighbour warp of that source alone,
clipped to its footprint. Only the sources off the target's pixels
pay for warping, and the cells are those the warper gives all the
sources together.
Usage
.mosaic_read_spec(paths, target_grid, band = 1L, nodata = numeric(0))Arguments
- paths
The source paths, in mosaic order.
- target_grid
The
WarpNodetargetGridSpec().- band
1-based band index (or indices) the read will use. Their data types drive the integer gate above.
- nodata
The source node's sentinel (length 0 or 1). Averaging declines unless the file declares the same value.
Value
NULL (the warper reads them together), or a list with
fx = fy = 1, resamp, the target grid and parts, one a source:
its .rio_direct_spec() result, or list(warp = TRUE), each with
box, its footprint in target pixels c(c0, r0, c1, r1).