diff --git a/core/models/survex.py b/core/models/survex.py
index a27ed45..cb5c26e 100644
--- a/core/models/survex.py
+++ b/core/models/survex.py
@@ -7,7 +7,7 @@ from pathlib import Path
 from django.conf import settings
 from django.db import models
 from django.urls import reverse
-from troggle.core.utils import height_from_utm
+from troggle.core.utils import height_from_utm, throw
 
 # from troggle.core.models.troggle import DataIssue # circular import. Hmm
 
@@ -100,8 +100,16 @@ class SurvexStation(models.Model):
             weight = "bold"
         else:
             weight = "normal"
+            
         diff_str = f"<span style='color:{colour}; font-weight:{weight}'>{sign}{diff:.0f}</span>"
-       
+        
+        if ref >= throw:
+            colour = "grey"
+            weight = "normal"
+            diff = "XX"
+            ref = float("nan")
+            diff_str = f"<span style='color:{colour}'>XX</span>"
+            
         return diff_str, ref
  
         
diff --git a/core/utils.py b/core/utils.py
index b46e341..0e0dfcc 100644
--- a/core/utils.py
+++ b/core/utils.py
@@ -38,6 +38,8 @@ TROG = {"pagecache": {"expedition": {}}, "caves": {"gcavelookup": {}, "gcavecoun
 alphabet = []
 sha = hashlib.new('sha256')
 
+throw = 35.0
+
 # This is module-level executable. This is a Bad Thing. Especially when it touches the file system.
 try:
     logging.basicConfig(level=logging.DEBUG, filename=settings.LOGFILE, filemode="w")
@@ -299,21 +301,25 @@ def find_nearest_point(points, target_point):
     In our dataset, the survey stations are all within 30m of an srtm reference point.
     So we can safely ignore points more than 100m away in either x or y directions.
     
+    This is not true for the 1624 and 1627 areas though.
+    
     TO DO: store this list twice, once sorted by x and once sorted by y,
     do a bounding box search for a set of nearby points before doing the exhaustive pythagorean distance search."""
     nearest_distance_squared = float("inf")
     nearest_point = None
     x_target, y_target = target_point
+    
+    max_ds = throw * throw # 1089 = 33 x 33
 
     for point in points:
         x, y, z = point
         if z < 0:
             distance_squared = 1000000.0 # ie ignore it
         else:
-            if x - x_target > 100:
-                distance_squared = 10000
-            elif y - y_target > 100:
-                distance_squared = 10000
+            if x - x_target > throw:
+                distance_squared = max_ds
+            elif y - y_target > throw:
+                distance_squared = max_ds
             else:
                 distance_squared = math.pow(x - x_target, 2) + math.pow(y - y_target, 2)