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Generate an Alphanumeric Survey Index Grid over an Area of Interest

Source: R/vantor_fieldwork.R
vantor_survey_grid.Rd

Partitions an Area of Interest (AOI) into a regular grid of square or hexagonal enumeration cells with human-readable alphanumeric index labels ("A1", "A2", "B1", etc.), cell centroids (centroid_lon, centroid_lat), and area in square meters (area_m2). Designed for planning field enumeration areas, printing map book index sheets with vantor_field_atlas(), and stratified spatial sampling.

Usage

vantor_survey_grid(
  aoi,
  cell_size = 500,
  shape = c("square", "hexagonal"),
  clip_to_aoi = TRUE,
  crs = 4326,
  verbose = getOption("vantorr.verbose", TRUE)
)

Arguments

aoi

A spatial object (sf, sfc, bbox, SpatRaster, SpatVector, SpatExtent, stars, stars_proxy) or a numeric bounding box vector of length 4 (c(xmin, ymin, xmax, ymax) in EPSG:4326).

cell_size

Numeric. Target width/diameter of each grid cell in meters (computed in Web Mercator EPSG:3857). Default is 500 (500 m).

shape

Character string. Grid cell geometry: "square" (default) or "hexagonal".

clip_to_aoi

Logical. If TRUE (default) and aoi is an sf, sfc, or SpatVector polygon, retains only grid cells that spatially intersect the aoi geometry.

crs

Numeric or character. Output Coordinate Reference System for the returned sf grid. Default is 4326 (EPSG:4326).

verbose

Logical. Print status messages. Default is getOption("vantorr.verbose", TRUE).

Value

An sf polygon object with columns:

  • cell_id: Alphanumeric grid label ("A1", "A2", ..., "B1", ...)

  • row_idx: Row index (top-to-bottom, 1-based)

  • col_idx: Column index (left-to-right, 1-based)

  • centroid_lon, centroid_lat: Cell centroid coordinates in EPSG:4326

  • area_m2: Approximate planar area in square meters

  • geometry: Polygon geometry in crs

Examples

aoi <- sf::st_bbox(
  c(xmin = -105.01, ymin = 39.73, xmax = -104.99, ymax = 39.75),
  crs = sf::st_crs(4326)
)
grid_sf <- vantor_survey_grid(aoi, cell_size = 500, verbose = FALSE)
head(grid_sf)
#> Simple feature collection with 6 features and 6 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -105.01 ymin: 39.74382 xmax: -104.9875 ymax: 39.75072
#> Geodetic CRS:  WGS 84
#>   cell_id row_idx col_idx centroid_lon centroid_lat area_m2
#> 1      A1       1       1    -105.0078     39.74900  250000
#> 2      A2       1       2    -105.0033     39.74900  250000
#> 3      A3       1       3    -104.9988     39.74900  250000
#> 4      A4       1       4    -104.9943     39.74900  250000
#> 5      A5       1       5    -104.9898     39.74900  250000
#> 6      B1       2       1    -105.0078     39.74554  250000
#>                         geometry
#> 1 POLYGON ((-105.01 39.74727,...
#> 2 POLYGON ((-105.0055 39.7472...
#> 3 POLYGON ((-105.001 39.74727...
#> 4 POLYGON ((-104.9965 39.7472...
#> 5 POLYGON ((-104.992 39.74727...
#> 6 POLYGON ((-105.01 39.74382,...