Page Summary
-
Extracts a stratified random sample of points from an image, returning a FeatureCollection where each Feature corresponds to an extracted point and has properties for each input image band.
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Samples a specified number of points for each distinct value in the 'classBand', but includes all points for a class if there are fewer than the requested number available.
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Requires the 'classBand' to contain integer values for successful operation.
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The sampling region, scale, projection, and the number of points per class can be customized using the method's arguments.
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Can optionally include geometries for each sampled pixel and allows for skipping pixels with masked bands.
| Usage | Returns |
|---|---|
Image.
stratifiedSample
(numPoints, classBand
, region
, scale
, projection
, seed
, classValues
, classPoints
, dropNulls
, tileScale
, geometries
)
|
FeatureCollection |
| Argument | Type | Details |
|---|---|---|
|
this:
image
|
Image | The image to sample. |
numPoints
|
Integer | The default number of points to sample in each class. Can be overridden for specific classes using the 'classValues' and 'classPoints' properties. |
classBand
|
String, default: null | The name of the band containing the classes to use for stratification. If unspecified, the first band of the input image is used. |
region
|
Geometry, default: null | The region to sample from. If unspecified, the input image's whole footprint is used. |
scale
|
Float, default: null | A nominal scale in meters of the projection to sample in. Defaults to the scale of the first band of the input image. |
projection
|
Projection, default: null | The projection in which to sample. If unspecified, the projection of the input image's first band is used. If specified in addition to scale, rescaled to the specified scale. |
seed
|
Integer, default: 0 | A randomization seed to use for subsampling. |
classValues
|
List, default: null | A list of class values for which to override the numPoints parameter. Must be the same size as classPoints or null. |
classPoints
|
List, default: null | A list of the per-class maximum number of pixels to sample for each class in the classValues list. Must be the same size as classValues or null. |
dropNulls
|
Boolean, default: true | Skip pixels in which any band is masked. |
tileScale
|
Float, default: 1 | A scaling factor used to reduce aggregation tile size; using a larger tileScale (e.g., 2 or 4) may enable computations that run out of memory with the default. |
geometries
|
Boolean, default: false | If true, the results will include a geometry per sampled pixel. Otherwise, geometries will be omitted (saving memory). |
