tiff_extract_points: Extract raster values at point coordinates

In vectra: Columnar Query Engine for Larger-than-RAM Data

Extract raster values at point coordinates

Description

Samples band values from a GeoTIFF at specific (x, y) locations using the file's affine geotransform. Only the strips containing query points are read, making this efficient for sparse point sets on large rasters.

Usage

tiff_extract_points(path, x, y = NULL)

Arguments

path	Path to a GeoTIFF file.
x	Numeric vector of x coordinates, or a data.frame / matrix with columns named x and y.
y	Numeric vector of y coordinates (ignored if x is a data.frame).

Details

Points that fall outside the raster extent return NA for all bands. Pixel assignment uses nearest-pixel rounding (i.e., the point is assigned to the pixel whose center is closest).

Value

A data.frame with columns x, y, band1, band2, etc. One row per input point, in the same order as the input.

Examples

f <- tempfile(fileext = ".tif")
df <- data.frame(x = as.double(rep(1:4, 3)),
                 y = as.double(rep(1:3, each = 4)),
                 band1 = as.double(1:12))
write_tiff(df, f)

# Sample at specific locations via data.frame
pts <- data.frame(x = c(2, 3), y = c(1, 2))
tiff_extract_points(f, pts)

# Or pass x and y separately
tiff_extract_points(f, x = c(2, 3), y = c(1, 2))
unlink(f)

vectra documentation built on May 8, 2026, 9:06 a.m.