diff --git a/modules/util/acspo_validate.py b/modules/util/acspo_validate.py
index 4ce224ad4ca9dec107569e87e1cedc0e62b209d2..d3fff2e347f422c160b688cb9e8f48a34fd23e49 100644
--- a/modules/util/acspo_validate.py
+++ b/modules/util/acspo_validate.py
@@ -65,14 +65,20 @@ def acspo_validate(oper_file, cspp_file, rel_tol=0.001, outfile_nc=None):
     # Average latitude spacing: 0.00652 deg
 
     for k in range(len(cntr_lat_oper)):
-        c_a = np.logical_and(np.isclose(cntr_lat_oper[k], cntr_lat_cspp), np.isclose(cntr_lon_oper[k], cntr_lon_cspp))
-        if np.size(np.nonzero(c_a)[0]) == 1:
+        c_a = np.isclose(cntr_lat_oper[k], cntr_lat_cspp)
+        if np.sum(c_a) == 1:
             if start_idx_oper == -1:
                 start_idx_oper = k
                 start_idx_cspp = np.nonzero(c_a)[0][0]
-            else:
+                break
+
+    for k in range(len(cntr_lat_oper)-1, 0, -1):
+        c_a = np.isclose(cntr_lat_oper[k], cntr_lat_cspp)
+        if np.sum(c_a) == 1:
+            if stop_idx_oper == -1:
                 stop_idx_oper = k
                 stop_idx_cspp = np.nonzero(c_a)[0][0]
+                break
 
     print('oper start, stop ', start_idx_oper, stop_idx_oper)
     print('cspp start, stop ', start_idx_cspp, stop_idx_cspp)