Sentinel 2 L2A: Add band assets for lower spatial res versions

stactools_sentinel2/stactools/sentinel2/constants.py

@@ -93,3 +93,57 @@
                 center_wavelength=2.190,
                 full_width_half_max=0.242),
 }
+
+# A dict describing the resolutions that are
+# available for each band as separate assets.
+# The first resolution is the sensor gsd; others
+# are downscaled versions.
+BANDS_TO_RESOLUTIONS = {
+    'B01': [
+        60,
+    ],
+    'B02': [
+        10,
+        20,
+        60,
+    ],
+    'B03': [
+        10,
+        20,
+        60,
+    ],
+    'B04': [
+        10,
+        20,
+        60,
+    ],
+    'B05': [
+        20,
+        20,
+        60,
+    ],
+    'B06': [
+        20,
+        60,
+    ],
+    'B07': [
+        20,
+        60,
+    ],
+    'B08': [
+        10,
+    ],
+    'B8A': [
+        20,
+        60,
+    ],
+    'B09': [60],
+    'B11': [
+        20,
+        60,
+    ],
+    'B12': [
+        20,
+        60,
+    ],
+}

stactools_sentinel2/stactools/sentinel2/stac.py

@@ -12,12 +12,10 @@
 from stactools.sentinel2.product_metadata import ProductMetadata
 from stactools.sentinel2.granule_metadata import GranuleMetadata
 from stactools.sentinel2.utils import extract_gsd
-from stactools.sentinel2.constants import (DATASTRIP_METADATA_ASSET_KEY,
-                                           SENTINEL_PROVIDER, SENTINEL_LICENSE,
-                                           SENTINEL_BANDS,
-                                           SENTINEL_INSTRUMENTS,
-                                           SENTINEL_CONSTELLATION,
-                                           INSPIRE_METADATA_ASSET_KEY)
+from stactools.sentinel2.constants import (
+    BANDS_TO_RESOLUTIONS, DATASTRIP_METADATA_ASSET_KEY, SENTINEL_PROVIDER,
+    SENTINEL_LICENSE, SENTINEL_BANDS, SENTINEL_INSTRUMENTS,
+    SENTINEL_CONSTELLATION, INSPIRE_METADATA_ASSET_KEY)
 
 logger = logging.getLogger(__name__)
 
@@ -172,29 +170,37 @@ def image_asset_from_href(
         return ('preview', asset)
 
     # Extract gsd and proj info
-    gsd = extract_gsd(asset_href)
-    shape = list(resolution_to_shape[int(gsd)])
+    filename_gsd = extract_gsd(asset_href)
+    shape = list(resolution_to_shape[int(filename_gsd)])
     transform = transform_from_bbox(proj_bbox, shape)
 
-    def set_asset_properties(asset):
-        item.common_metadata.set_gsd(gsd, asset)
+    def set_asset_properties(asset: pystac.Asset, band_gsd: Optional[int] = None):
+        if filename_gsd is None:
+            item.common_metadata.set_gsd(filename_gsd, asset)
+        else:
+            item.common_metadata.set_gsd(band_gsd, asset)
         item.ext.projection.set_shape(shape, asset)
         item.ext.projection.set_bbox(proj_bbox, asset)
         item.ext.projection.set_transform(transform, asset)
 
     # Handle band image
 
-    band_id_search = re.search(r'_(B\w{2})_', asset_href)
+    band_id_search = re.search(r'_(B\w{2})', asset_href)
     if band_id_search is not None:
-        band_id = band_id_search.group(1)
+        band_id, href_res = os.path.splitext(asset_href)[0].split('_')[-2:]
+        asset_res = int(href_res.replace('m', ''))
         band = SENTINEL_BANDS[band_id]
+        if asset_res == BANDS_TO_RESOLUTIONS[band_id][0]:
+            asset_key = band_id
+        else:
+            asset_key = f'{band_id}_{asset_res}m'
         asset = pystac.Asset(href=asset_href,
                              media_type=asset_media_type,
-                             title=band.description,
+                             title=f'{band.description} - {href_res}',
                              roles=['data'])
         item.ext.eo.set_bands([SENTINEL_BANDS[band_id]], asset)
-        set_asset_properties(asset)
-        return (band_id, asset)
+        set_asset_properties(asset, band_gsd=BANDS_TO_RESOLUTIONS[band_id][0])
+        return (asset_key, asset)
 
     # Handle auxiliary images
 

tests/sentinel2/test_commands.py

@@ -1,3 +1,4 @@
+from collections import defaultdict
 import os
 from tempfile import TemporaryDirectory
 
@@ -7,7 +8,7 @@
 
 from stactools.core.projection import reproject_geom
 from stactools.sentinel2.commands import create_sentinel2_command
-from stactools.sentinel2.constants import SENTINEL_BANDS
+from stactools.sentinel2.constants import BANDS_TO_RESOLUTIONS, SENTINEL_BANDS
 from tests.utils import (TestData, CliTestCase)
 
 
@@ -58,13 +59,50 @@ def check_proj_bbox(item):
                     item.validate()
 
                     bands_seen = set()
+                    bands_to_assets = defaultdict(list)
 
-                    for asset in item.assets.values():
+                    for key, asset in item.assets.items():
                         self.assertTrue(is_absolute_href(asset.href))
                         bands = item.ext.eo.get_bands(asset)
                         if bands is not None:
                             bands_seen |= set(b.name for b in bands)
+                            if key.split('_')[0] in SENTINEL_BANDS:
+                                for b in bands:
+                                    bands_to_assets[b.name].append(
+                                        (key, asset))
 
                     self.assertEqual(bands_seen, set(SENTINEL_BANDS.keys()))
 
+                    # Check that multiple resolutions exist for assets that
+                    # have them, and that they are named such that the highest
+                    # resolution asset is the band name, and others are
+                    # appended with the resolution.
+
+                    resolutions_seen = defaultdict(list)
+
+                    for band_name, assets in bands_to_assets.items():
+                        for (asset_key, asset) in assets:
+                            resolutions = BANDS_TO_RESOLUTIONS[band_name]
+
+                            asset_split = asset_key.split('_')
+                            self.assertLessEqual(len(asset_split), 2)
+
+                            href_band, href_res = os.path.splitext(
+                                asset.href)[0].split('_')[-2:]
+                            asset_res = int(href_res.replace('m', ''))
+                            self.assertEqual(href_band, band_name)
+                            if len(asset_split) == 1:
+                                self.assertEqual(asset_res, resolutions[0])
+                                resolutions_seen[band_name].append(asset_res)
+                            else:
+                                self.assertNotEqual(asset_res, resolutions[0])
+                                self.assertIn(asset_res, resolutions)
+                                resolutions_seen[band_name].append(asset_res)
+
+                    self.assertEqual(set(resolutions_seen.keys()),
+                                     set(BANDS_TO_RESOLUTIONS.keys()))
+                    for band in resolutions_seen:
+                        self.assertEqual(set(resolutions_seen[band]),
+                                         set(BANDS_TO_RESOLUTIONS[band]))
+
                     check_proj_bbox(item)