snapshot...

modules/util/lon_lat_grid.py

@@ -19,7 +19,7 @@ class MyGenericException(Exception):
 class LonLatGrid:
     # grd_lons, grd_lats: the longitude, latitude of each grid point (must be 2D grids), must have same shape
     # Incoming longitude must be in range: 0 - 360 degrees
-    # Can have NaN for off Earth grid points.
+    # Can have NaN for off Earth grid points (these are handled internally).
     def __init__(self, grd_lons, grd_lats):
         if grd_lons.shape != grd_lats.shape:
             raise MyGenericException('incoming lons,lats must have same shape')
@@ -50,9 +50,10 @@ class LonLatGrid:
 
     # locate nearest neighbor for incoming target in earth coordinates (Should not have NaNs)
     # lons, lats can be flat or 2D
+    # closeness_threshold: if < distance of located_point to target, return off grid
     # incoming longitude must be in range: 0 - 360 degrees
     # returns NN indexes relative to the grid determined in the ctr.
-    def value_to_index(self, lons, lats):
+    def value_to_index(self, lons, lats, closeness_threshold=2000):
         if lons.shape != lats.shape:
             raise MyGenericException('incoming lons,lats must have same shape')
 
@@ -65,8 +66,9 @@ class LonLatGrid:
         xy = np.stack([lons, lats], axis=1)
 
         dist, indices = self.kd.query(np.deg2rad(xy))
+        dist *= 6370000  # convert unit radius to meters
 
-        valid = indices < self.map_indexes.size
+        valid = (indices < self.map_indexes.size) & (dist < closeness_threshold)
         indices = indices[valid]
 
         return self.map_indexes[indices], indices