README.md

In AndyPL22/TileManager: Tile Manager

TileManager: Tools for creating and detecting tiling schemes for geospatial datasets

Authors: Andrew Plowright License: GPL 3

This package provides tools for working with tiled geospatial datasets.

News

2024-03-08, v.1.0.0

The latest release of TileManager is a complete refactor of the old library, which used the obsolete raster and sp packages. The new version uses terra and sf instead. Although the structure of the tileScheme class remains similar, any spatial outputs from this library now use sf formats.

Furthermore, tileScheme objects are now saved to the Geopackage format instead of SHP files.

Introduction

Use the tileScheme function to create a set of tiles from a Raster or Extent object.

library(TileManager)
library(terra)
#> Warning: package 'terra' was built under R version 4.3.2
#> terra 1.7.65

# Load a test raster
chm <- rast(system.file("ex/chm.tif", package="TileManager"))

# Generate a tile scheme
ts <- tileScheme(chm, dim = c(30,30), buffer = 5)

plot(chm)
plot(ts, add = T)

Use the remove_empty argument to drop tiles with no Raster values.

ts <- tileScheme(chm, dim = c(20,20), buffer = 2.5, remove_empty = TRUE)

plot(chm)
plot(ts, add = T)

Other handy features:

• The origin argument can be used to force the tile scheme to snap to a pair of coordinates.
• The spill argument controls whether or not the buffers extent beyond the input’s original extent.
• By default, tile dimensions are in map units. Using the cells argument, they can be defined by a number of Raster cells.

Non-overlapping buffers

Non-overlapping buffers (often abbreviated to nbuffs) are useful for re-assembling tiled data. Essentially, they preserve buffers only where they do not overlap onto neighboring tiles (i.e.: along the edge of the tile scheme). This allows you to recombine tiles without worrying about overlapping areas and without losing any information along the data edges.

In the example below:

• The solid blue is the tile
• The dashed red is the buffer
• The solid purple is the non-overlapping buffer

Methods

Some useful methods are provided for subsetting the tile scheme, or for converting it into other formats.

Get buffers as a sf object:

ts[["buffs"]]
#> Simple feature collection with 32 features and 3 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 439872.8 ymin: 5526636 xmax: 440015.2 ymax: 5526753
#> Projected CRS: WGS 84 / UTM zone 11N
#> First 10 features:
#>      row col tile_name                          buffs
#> R1C1   1   1      R1C1 POLYGON ((439872.8 5526728,...
#> R1C3   1   3      R1C3 POLYGON ((439912.8 5526728,...
#> R1C4   1   4      R1C4 POLYGON ((439932.8 5526728,...
#> R2C1   2   1      R2C1 POLYGON ((439872.8 5526708,...
#> R2C2   2   2      R2C2 POLYGON ((439892.8 5526708,...
#> R2C3   2   3      R2C3 POLYGON ((439912.8 5526708,...
#> R2C4   2   4      R2C4 POLYGON ((439932.8 5526708,...
#> R2C5   2   5      R2C5 POLYGON ((439952.8 5526708,...
#> R3C1   3   1      R3C1 POLYGON ((439872.8 5526688,...
#> R3C2   3   2      R3C2 POLYGON ((439892.8 5526688,...

Subset a specific tile by name, number or row/col:

# By name
ts["R2C2"]
#> class     : tileScheme
#> extent    : 439895.25, 5526710.75, 439915.25, 5526733.25 (xmin, ymin, xmax, ymax)
#> CRS       : WGS 84 / UTM zone 11N
#> tiles     : 1
#> nrow/ncol : 1,1
#> buffer    : 2.5

# By number
ts[7]
#> class     : tileScheme
#> extent    : 439935.25, 5526710.75, 439955.25, 5526730.75 (xmin, ymin, xmax, ymax)
#> CRS       : WGS 84 / UTM zone 11N
#> tiles     : 1
#> nrow/ncol : 1,1
#> buffer    : 2.5

# By row/col
ts[2,3]
#> class     : tileScheme
#> extent    : 439915.25, 5526710.75, 439935.25, 5526730.75 (xmin, ymin, xmax, ymax)
#> CRS       : WGS 84 / UTM zone 11N
#> tiles     : 1
#> nrow/ncol : 1,1
#> buffer    : 2.5

Subset entire rows or columns:

# One row
ts[4,]
#> class     : tileScheme
#> extent    : 439872.75, 5526670.75, 439977.75, 5526690.75 (xmin, ymin, xmax, ymax)
#> CRS       : WGS 84 / UTM zone 11N
#> tiles     : 5
#> nrow/ncol : 1,5
#> buffer    : 2.5

# Multiple columns
ts[,2:3]
#> class     : tileScheme
#> extent    : 439895.25, 5526635.5, 439935.25, 5526753.25 (xmin, ymin, xmax, ymax)
#> CRS       : WGS 84 / UTM zone 11N
#> tiles     : 11
#> nrow/ncol : 6,2
#> buffer    : 2.5

Saving and loading

The tile scheme can be saved as a single Geopackage. In this case, tiles, buffs and nbuffs will all be written to separate tables. Other metadata (such as the buffer size) are written to a metadata table.

# Create tile scheme
ts <- tileScheme(chm, dim = c(30,30), buffer = 5)

# Save tile scheme
tileSave(ts, "C:/myfiles/tilescheme.gpkg")

# Load tile scheme
ts <- tileLoad("C:/myfiles/tilescheme.gpkg")

AndyPL22/TileManager documentation built on March 11, 2024, 11:52 a.m.