Calculate Global Surface Water (GSW) Change

The change in water occurrence intensity between the two periods is derived from homologous pairs of months (i.e. same months containing valid observations in both periods). The difference in the occurrence of surface water was calculated for each homologous pair of months. The average of all of these differences constitutes the Surface Water Occurrence change intensity. The raster files have integer cell values between [0, 200] where 0 represents surface water loss and 200 represents surface water gain.

Usage

calc_gsw_change(engine = "extract", stats = "mean")

Arguments

engine

The preferred processing functions from either one of "zonal", "extract" or "exactextract". Default: "extract".

stats

Aggregation function with which the data are combined. Default: "mean".

Value

A function that returns an indicator tibble with change intensity as variable and corresponding (unitless) values as value.

Details

The pixel values are aggregated using method provided via the stats parameter using the specified engine.

The required resources for this indicator are:

• global_surface_water_change

Examples

# \dontrun{
library(sf)
library(mapme.biodiversity)

outdir <- file.path(tempdir(), "mapme-data")
dir.create(outdir, showWarnings = FALSE)

mapme_options(
  outdir = outdir,
  verbose = FALSE
)

aoi <- system.file("extdata", "shell_beach_protected_area_41057_B.gpkg",
  package = "mapme.biodiversity"
) %>%
  read_sf() %>%
  get_resources(get_global_surface_water_change()) %>%
  calc_indicators(
    calc_gsw_change(engine = "extract", stats = "mean")
  ) %>%
  portfolio_long()

aoi
#> Simple feature collection with 1 feature and 10 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -59.84866 ymin: 8.307999 xmax: -59.71 ymax: 8.364002
#> Geodetic CRS:  WGS 84
#> # A tibble: 1 × 11
#>   WDPAID NAME     DESIG_ENG ISO3  assetid indicator datetime            variable
#>    <dbl> <chr>    <chr>     <chr>   <int> <chr>     <dttm>              <chr>   
#> 1  41057 Shell B… Managed … GUY         1 gsw_chan… 2021-01-01 00:00:00 gsw_cha…
#> # ℹ 3 more variables: unit <chr>, value <dbl>, geom <POLYGON [°]>
# }