azimuth_image: Build azimuth image

In rcaiman: CAnopy IMage ANalysis

Build azimuth image

Description

Creates a single-layer raster in which pixel values represent azimuth angles, assuming an upwards-looking hemispherical photograph with the optical axis vertically aligned.

Usage

azimuth_image(z, orientation = 0)

Arguments

z	terra::SpatRaster generated with zenith_image().
orientation	numeric vector of length one. Azimuth angle (in degrees) corresponding to the direction at which the top of the image was pointing when the picture was taken. This design follows the common field protocol of recording the angle at which the top of the camera points.

Value

terra::SpatRaster with the same dimensions as the input zenith image. Each pixel contains the azimuth angle in degrees, with zero representing North and angles increasing counter-clockwise. The object carries attributes orientation and lens_coef.

Note

If orientation = 0, North (0 deg) is located at the top of the image, as in conventional maps, but East (90 deg) and West (270 deg) appear flipped relative to maps. To understand this, take two flash-card-sized pieces of paper. Place one on a table in front of you and draw a compass rose on it. Hold the other above your head, with the side facing down toward you, and draw another compass rose following the directions from the one on the table. This mimics the situation of taking an upwards-looking photo with a smartphone while viewing the screen, and it will result in a mirrored arrangement. Compare both drawings to see the inversion.

Examples

z <- zenith_image(600, lens("Nikon_FCE9"))
a <- azimuth_image(z)
plot(a)
## Not run: 
a <- azimuth_image(z, 45)
plot(a)

## End(Not run)

rcaiman documentation built on Sept. 9, 2025, 5:42 p.m.