statgis.gee.sample#

Sample pixel values from image in a region of interest

Module Contents#

Functions#

sample_image(→ numpy.typing.ArrayLike)

Sample all pixels from an image in the specified band.

sample_collection(→ list)

This function sample all images in an image collection applying the sample_image
statgis.gee.sample.sample_image(image: ee.Image, geom: ee.Geometry, scale: float, band: str) → numpy.typing.ArrayLike#

Sample all pixels from an image in the specified band.

Parameters:

  • image (ee.Image) – Image to sample.

  • geom (ee.Geometry) – Region of interest.

  • scale (float) – Scale of image to sample.

  • band (str) – Band of interest.

Returns:

data – Array with the sampled values.

Return type:

np.array

Example

>>> import ee
>>> from statgis.gee import sample, landsat_functions, time_series_analysis
>>> ee.Initialize()
>>> roi = ee.Geometry.BBox(-76.6854802, 3.3903932, -76.6904802, 3.3953932)
>>> landsat_collection = ee.ImageCollection([])
>>> for code in ["LT05", "LE07", "LC08", "LC09"]:
...     landsat_collection = landsat_collection.merge(
...         ee.ImageCollection(f"LANDSAT/{code}/C02/T1_L2")
...         .filterBounds(roi)
...         .filterDate("1995-01-01", "2022-12-31")
...         .map(landsat_functions.scaler)
...         .map(landsat_functions.cloud_mask)
...         .map(landsat_functions.rename_bands)
...         .map(lambda img: img.addBands(img.normalizedDifference(["NIR", "RED"]).rename("NDVI")))
...     )
>>> image = landsat_collection.mean()
>>> mean_ndvi_values = sample.sample_image(image, roi, 30, "NDVI")
statgis.gee.sample.sample_collection(image_collection: ee.ImageCollection, geom: ee.Geometry, scale: float, band: str) → list#

This function sample all images in an image collection applying the sample_image function to all images.

Parameters:

  • image_collection (ee.ImageCollection) – Image collection to sample.

  • geom (ee.Geometry) – Region of interest.

  • scale (float) – Scale of image to sample.

  • band (str) – Band of interest.

Returns:

data – list of np.array with all the sampled values per image.

Return type:

list

Example

>>> import ee
>>> from statgis.gee import sample, landsat_functions, time_series_analysis
>>> ee.Initialize()
>>> roi = ee.Geometry.BBox(-76.6854802, 3.3903932, -76.6904802, 3.3953932)
>>> landsat_collection = ee.ImageCollection([])
>>> for code in ["LT05", "LE07", "LC08", "LC09"]:
...     landsat_collection = landsat_collection.merge(
...         ee.ImageCollection(f"LANDSAT/{code}/C02/T1_L2")
...         .filterBounds(roi)
...         .filterDate("1995-01-01", "2022-12-31")
...         .map(landsat_functions.scaler)
...         .map(landsat_functions.cloud_mask)
...         .map(landsat_functions.rename_bands)
...         .map(lambda img: img.addBands(img.normalizedDifference(["NIR", "RED"]).rename("NDVI")))
...     )
>>> annual_ndvi = time_series_analysis.resample(landsat_collection, ee.Reducer.median(), "annual")
>>> annual_ndvi_values = sample.sample_collection(annual_ndvi, roi, 30, "NDVI")