LAI_from_gf_at_57: Calculate leaf area index (LAI) from an image in a band...

In cmartin/LAI: Calculate indirect Leaf Area Index (LAI) from images

Description

This functions first seperates sky from vegetation pixels using unimodal_threshold. Based on the focal angle and camera field of view provided, it then extracts a narrow band around a 57.5 degrees zenith angle (Baret et al. 2010). The gap_fraction of this band is then used to calculated an indirect LAI value (e.g. Confalonieri et al. 2013).

Usage

LAI_from_gf_at_57(image_path, camera_horiz_FOV = 73.7, focal_angle = 45)

Arguments

image_path	Path to the image to analyze.
camera_horiz_FOV	Camera horizontal field of view (in degrees)
focal_angle	Angle at which the camera was pointing (degrees). 0 is horizontal, 90 is vertical

Value

The calculated LAI value.

References

Baret, F., de Solan, B., Lopez-Lozano, R., Ma, K., & Weiss, M. (2010). GAI estimates of row crops from downward looking digital photos taken perpendicular to rows at 57.5 zenith angle: Theoretical considerations based on 3D architecture models and application to wheat crops. Agricultural and Forest Meteorology, 150(11), 1393-1401.

Confalonieri, R., Foi, M., Casa, R., Aquaro, S., Tona, E., Peterle, M., ... Acutis, M. (2013). Development of an app for estimating leaf area index using a smartphone. Trueness and precision determination and comparison with other indirect methods. Computers and Electronics in Agriculture, 96, 67-74.

See Also

unimodal_threshold gap_fraction

Examples

## @knitr LAIExample

library(raster)

test_image <-  system.file("extdata", "IMG_7595.JPG", package = "LAI")

# See the image
plotRGB(
  brick(test_image),
  asp = 1
)

# Calculate LAI
LAI_from_gf_at_57(test_image)

cmartin/LAI documentation built on May 13, 2019, 8:23 p.m.