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Create spatial calibration from a digitized scale reference

Source: R/hsi_calibration_from_scale.R
hsi_calibration_from_scale.Rd

Create a spatial calibration by measuring a known-length reference digitized in GIS software. The function calculates pixel distance from the geometry and derives resolution from the provided physical distance.

Usage

hsi_calibration_from_scale(x, distance = 10000, units = "um")

Arguments

x

A SpatVector representing a digitized scale reference. Must be either a line geometry or exactly 2 points. CRS must be NULL (pixel coordinates).

distance

Numeric. Physical distance the reference represents. Single positive value. Default 10000.

units

Character. Units of the provided distance. One of "um" (micrometers), "mm", or "cm". Default "um".

Value

A named numeric with resolution in µm/px, named "um_per_px".

Details

The input SpatVector can be a line drawn along the reference, or two points placed at the reference endpoints. CRS must be NULL because coordinates are in pixel space.

See also

Other HSI Calibration: hsi_calibration_direct(), hsi_calibration_from_dims(), hsi_drop_crs(), hsi_pixels_to_units(), hsi_set_extent()

Examples

if (FALSE) { # \dontrun{
scale_line <- terra::vect("scale.gpkg", layer = "scale")

calibration <- hsi_calibration_from_scale(
  scale_line,
  distance = 10,
  units = "mm"
)

scale_points <- terra::vect("points.gpkg", layer = "scale_points")

calibration <- hsi_calibration_from_scale(
  scale_points,
  distance = 10000,
  units = "um"
)
} # }