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Calculate Soil Moisture Grid, Exponential Trapezoid

Source: R/trapezoid_utilities.R
exponential_soil_moisture.Rd

Prepare soil moisture grid from STR and VI images for a single date, based on exponential function to derive trapezoid edges, using the derived slope and intercept coefficients

Usage

exponential_soil_moisture(coeffs, VI, STR)

Arguments

coeffs,

list, 4 trapezoid coefficients

VI,

terra rast, the vegetation index raster

STR,

terra rast, the STR raster

Value

rast, soil moisture grid

Note

This function is used after preparing the OPTRAM model coefficients with: optram_wetdry_coefficients. Typically a new image date, (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. This function implements an exponential trapezoid, following: 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

Examples

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