geo_index: Compute a Spectral Index from Multispectral Raster Data

In GeoIndexR: Computation of Spectral and Geospatial Indices from Multispectral Raster Data

Compute a Spectral Index from Multispectral Raster Data

Description

Calculates a specified spectral or geospatial index from a terra::SpatRaster object or a raster file path. Band names are automatically resolved using heuristic matching, sensor presets, or explicit user mapping.

Usage

geo_index(image, index, bands = NULL, scale_factor = NULL, sensor = NULL, ...)

Arguments

image	A terra::SpatRaster object or a character string specifying the file path to a raster image on disk.
index	Character string specifying the index to compute (case-insensitive, e.g., "NDVI", "SAVI", "EVI", "NDWI", etc.). See list_indices or index_registry for supported indices.
bands	Optional named vector or list specifying custom band mapping (e.g., c(nir = "B08", red = "B04") or c(nir = 4, red = 3)).
scale_factor	Optional numeric scaling divisor (e.g., 10000 for Sentinel-2 L2A or Landsat surface reflectance) to convert integer Digital Numbers into physical reflectance [0, 1].
sensor	Optional character string specifying a sensor preset for automatic band name resolution (e.g., "sentinel2", "landsat8", "landsat9").
...	Additional parameters passed to the index calculation function (e.g., soil adjustment factor L for SAVI, or gain factor G for EVI).

Value

A single-layer terra::SpatRaster object containing the computed index values, with layer name set to the uppercase index code, preserving all original spatial properties (CRS, resolution, extent, dimensions).

Examples

img <- get_example_data()

# 1. Compute NDVI
ndvi <- geo_index(img, "NDVI")
print(ndvi)

# 2. Compute SAVI with custom parameter
savi <- geo_index(img, "SAVI", L = 0.5)

# 3. Compute EVI with scale factor for raw DN values
evi <- geo_index(img, "EVI", scale_factor = 1)

GeoIndexR documentation built on Oct. 10, 2026, 5:08 p.m.