Extract Values to Points

Draft: written, not yet checked by a person Operation · extract-values-to-points

Adds to each point the value of the raster at its location.

Pitfall. Points and raster in different CRSs give wrong or empty values unless the engine reprojects the points first.

Pitfall. Some engines interpolate by default, so values differ from the cell's value except at cell centres.

Pitfall. Points outside the raster or on nodata cells get nodata, null or an error depending on the engine.

About this operation
Also called	sample raster values, raster sampling, point query, Extract Multi Values to Points, drill a raster
Group	`raster/extraction`
Checks	`crs.agreement, raster.nodata`
Pitfalls	3 listed above
Columbus tool	Not stated
Notes	Not stated
Status	active
Broader	Not stated
Narrower	Not stated
Related	`zonal-statistics`

Parameters

Name	Type	Required	Default	Values	Note
`resampling`	enum	no	`nearest`	`nearest, bilinear`	nearest: the value of the cell the point falls in; bilinear: interpolated from the four nearest cell centres.

Inputs and outputs

Direction	Name	Type	Geometry	Note
Input	`points`	vector	point	Not stated
Input	`raster`	raster	Not stated	Not stated
Output	`output`	vector	point	Not stated

In each engine

Engine	Tool	Parameters	Differences
`gdal`	`gdal raster pixel-info`	`resampling` → `resampling` `raster` → `input` `points` → `position-dataset` `output` → `output`	Takes positions as coordinates (position) or from a vector dataset (position-dataset); writes the points with the values as fields.
`grass`	`v.what.rast`	`resampling` → `flag_i` : nearest = no; bilinear = yes `raster` → `raster` `points` → `map`	Updates a column of the point map's attribute table, which must exist first (v.db.addcolumn); flag p prints the values instead.
`postgis-raster`	`st_value`	`resampling` → `resample` `raster` → `rast` `points` → `pt`	Returns the value at one point; run it once per point row. resample also offers cubic and cubic spline interpolation. Preset: `{"band":1}`
`qgis`	`native:rastersampling`	`resampling` always nearest `raster` → `RASTERCOPY` `points` → `INPUT` `output` → `OUTPUT`	Adds one field per band, named COLUMN_PREFIX plus the band number (SAMPLE_1).
`rasterio`	`rasterio.sample.sample_gen`	`resampling` always nearest `raster` → `dataset` `points` → `xy` : An iterable of (x, y) coordinate pairs in the raster's CRS.	Yields an array of band values per point; DatasetReader.sample is the same as a method of an open raster.
`rasterstats`	`rasterstats.gen_point_query`	`resampling` → `interpolate` `raster` → `raster` `points` → `vectors`	Interpolates (bilinear) by default; returns one value per point (a generator; point_query returns a list).
`terra`	`terra::extract`	`resampling` → `method` : nearest = simple; bilinear = bilinear `raster` → `x` `points` → `y`	Returns a data frame of ID and one column per layer, not the points; bind = TRUE returns the points with the values.
`whiteboxtools`	`ExtractRasterValuesAtPoints`	`resampling` always nearest `raster` → `inputs` `points` → `points`	Writes VALUE1, VALUE2, ... (one per raster) into the points file itself; out_text also prints them.