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Calculate Soil Moisture Grid

Source: R/optram_soilmoisture.R
optram_calculate_soil_moisture.Rd

Prepare soil moisture grid from STR and VI images for a single date using the derived slope and intercept coefficients

Usage

optram_calculate_soil_moisture(
  img_date,
  VI_dir,
  STR_dir,
  data_dir,
  output_dir = tempdir()
)

Arguments

img_date,

string, image date of single Sentinel 2 acquisition formatted as "YYYY-MM-DD"

VI_dir,

string, full path to directory holding the VI rasters

STR_dir,

string, full path to directory holding the STR rasters

data_dir,

string, the directory where coefficients file was saved (the output_dir parameter in optram_wetdry_coefficients function)

output_dir,

string, full path to output directory for saving soil moisture raster

Value

SpatRaster, raster of soil moisture, file(s) saved in output_dir

Note

This function is used after preparing the OPTRAM model coefficients with: optram_wetdry_coefficients. Typically a new image date, (possibly an image that was not used for preparing the model), will be referenced in the img_date parameter. The resulting soil moisture raster is saved to output_dir.

Three trapezoid models are offered through the trapezoid_method option: either "linear", "exponential", or "polynomial". (set using optram_options) The data_dir parameter is a directory name. The coefficients CSV file that matches trapezoid_method should be in that directory

For further details see: Ambrosone, Mariapaola, et al. 2020. “Retrieving Soil Moisture in Rainfed and Irrigated Fields Using Sentinel-2 Observations and a Modified OPTRAM Approach.” International Journal of Applied Earth Observation and Geoinformation 89 (July): 102113. doi:10.1016/j.jag.2020.102113 .

The data_dir directory must contain the coefficients CSV file i.e. for "linear" method the file was saved as 'coefficients_lin.csv' for "exponential" it was saved as 'coefficients_exp.csv' for "polynomial" it was saved as 'coefficients_poly.csv'

Examples

img_date <- "2023-03-11"
VI_dir <- system.file("extdata", "NDVI", package = "rOPTRAM")
STR_dir <- system.file("extdata", "STR", package = "rOPTRAM")
data_dir <- system.file("extdata")
SM <- optram_calculate_soil_moisture(img_date,
      VI_dir, STR_dir, data_dir)
#> No data directory: