grid reuse

helpers/ReadVIIRSNTL.py

@@ -28,19 +28,16 @@ from PIL import Image
 import rasterio as rio
 from huggingface_hub import hf_hub_download
 
-from .grid import *
-
 # ==============================================================================
 # 3. Dataset configuration & remote index (lazy)
 # ==============================================================================
 REPO_ID   = "Major-TOM/Core-VIIRS-Nighttime-Light"
 REPO_BASE = f"https://huggingface.co/datasets/{REPO_ID}/resolve/main"
 
-mt_grid = Grid(10, latitude_range=(-90, 90), longitude_range=(-180, 180))
-
-# The index is loaded on first use rather than at import time, so the
-# Space's startup memory budget isn't pushed up by ~500 MB before the
-# user has even asked for a VIIRS tile.
+# Both the index and the Major TOM grid object are loaded lazily so this
+# module's import has zero side effects. The grid is a ~1 GB GeoDataFrame
+# instantiated by Grid.__init__; we borrow the instance ReadAlphaEarth
+# already created in the Space rather than building a third copy.
 _viirs_df = None
 
 def _get_viirs_df():
@@ -96,6 +93,9 @@ def cell_to_viirs(cell, year, return_centre=False, return_gridcell=False, return
         is not in the index or the read fails.
     """
     row, col = cell.split('_')
+    # Reuse the Grid instance ReadAlphaEarth already built — avoids
+    # allocating a second multi-GB GeoDataFrame.
+    from .ReadAlphaEarth import mt_grid
     lats, lons = mt_grid.rowcol2latlon([row], [col])
 
     try: