diff --git a/pierzainer_ground/pierzainer_ground/survey_terrain.py b/pierzainer_ground/pierzainer_ground/survey_terrain.py
index 66d6595..26eec2e 100644
--- a/pierzainer_ground/pierzainer_ground/survey_terrain.py
+++ b/pierzainer_ground/pierzainer_ground/survey_terrain.py
@@ -17,6 +17,45 @@ from pierzainer_ground.dtm import DTM
 ROOT=Path(__file__).resolve().parent.parent
 
 
+def reject_height_outliers(entities, radius=15.0, max_dz=10.0, min_levels=3, same=1e-3):
+    """Drop height entities that disagree with the surrounding surveyed surface.
+
+    Drawings often keep plan symbols, hatching or design outlines at a stray
+    constant elevation (e.g. EL 5.624 or -112.719 among 20-40 m contours).
+    Each entity's height is compared with the median of the *distinct* nearby
+    height levels (each level votes once, so a dense stray group of short
+    ticks cannot outvote real contours); the worst height level is removed
+    first and the test is repeated, so a large stray group cannot mask itself.
+    Sparse areas fall back to a 3x search radius.
+    Heights within `same` (1 mm) form one level, absorbing CAD float noise.
+    Returns (keep flags, [(index, z, deviation)]).
+    """
+    from scipy.spatial import cKDTree
+    n=len(entities)
+    keep=np.ones(n,bool)
+    if n<3:return keep.tolist(),[]
+    xy=np.vstack([e[0] for e in entities]);owner=np.concatenate([np.full(len(e[0]),i) for i,e in enumerate(entities)])
+    zs=np.array([float(e[1]) for e in entities]);sample_z=zs[owner]
+    tree=cKDTree(xy);rejected=[]
+    near=lambda e,r:np.unique(np.concatenate(tree.query_ball_point(e[0],r)) if len(e[0]) else np.array([],int)).astype(int)
+    neighbours=[near(e,radius) for e in entities];wide=[near(e,3*radius) for e in entities]
+    for _ in range(64):
+        alive=keep[owner];dev=np.zeros(n)
+        for i in np.flatnonzero(keep):
+            nb=neighbours[i];nb=nb[alive[nb]&(np.abs(sample_z[nb]-zs[i])>same)]
+            if len(np.unique(np.round(sample_z[nb]/same)))<min_levels:nb=wide[i];nb=nb[alive[nb]&(np.abs(sample_z[nb]-zs[i])>same)]
+            levels=np.unique(np.round(sample_z[nb]/same))*same
+            # Peaks/pits legitimately exceed the median; require the height to
+            # lie clearly outside the whole local range as well.
+            outside=max(levels[0]-zs[i],zs[i]-levels[-1]) if len(levels) else 0.0
+            if len(levels)>=min_levels and outside>max_dz/2:dev[i]=zs[i]-float(np.median(levels))
+        worst=int(np.argmax(np.abs(dev)))
+        if abs(dev[worst])<=max_dz:break
+        group=np.flatnonzero(keep&(np.abs(zs-zs[worst])<=same)&(np.abs(dev)>max_dz))
+        keep[group]=False;rejected.extend((int(i),float(zs[i]),float(dev[i])) for i in group)
+    return keep.tolist(),rejected
+
+
 def read_survey_block(source, project, doc=None):
     """Read actual height geometry in an explicitly selected survey block."""
     if doc is None:
@@ -54,9 +93,11 @@ def read_survey_block(source, project, doc=None):
                 if e.is_closed: xy.append(xy[0])
                 contours.append((xy,float(a[0,2]),e.dxf.handle)); types['constant_height_polylines']+=1
     # POINT entities have priority over densified contour vertices.
-    for xy,z,handle in contours:
-        samples=_densify(xy,project['contour_step_m'])
-        points.extend((x,y,z) for x,y in samples)
+    sampled=[(np.asarray(_densify(xy,project['contour_step_m']),dtype=float).reshape(-1,2),z) for xy,z,handle in contours]
+    sampled=[(np.array([[x,y]]),z) for x,y,z in points]+sampled
+    keep,rejected=reject_height_outliers(sampled,project.get('outlier_radius_m',15.0),project.get('outlier_dz_m',10.0)) if project.get('reject_outliers',True) else ([True]*len(sampled),[])
+    if rejected:types['rejected_height_outliers']=len(rejected)
+    points=[(x,y,z) for (xy,z),ok in zip(sampled,keep) if ok for x,y in xy]
     a=np.array(points,dtype=float)
     if len(a)<3:
         raise ValueError('선택한 블록에서 실제 표고점·등고선을 3점 이상 읽지 못했습니다.')
diff --git a/pierzainer_ground/tests/test_survey_polyline.py b/pierzainer_ground/tests/test_survey_polyline.py
index eff83ca..cd9e740 100644
--- a/pierzainer_ground/tests/test_survey_polyline.py
+++ b/pierzainer_ground/tests/test_survey_polyline.py
@@ -25,4 +25,23 @@ class SurveyPolylineTests(unittest.TestCase):
         doc=ezdxf.new();doc.modelspace().add_polyline3d([(1,1,20),(2,2,30),(3,3,40)])
         with self.assertRaises(ValueError):read_survey_block(Path('unused.dxf'),self.options(),doc=doc)
 
+    def contours(self,msp,levels):
+        for k,z in enumerate(levels):
+            msp.add_lwpolyline([(0,10*k),(200,10*k)],dxfattribs={'elevation':z})
+
+    def test_stray_constant_height_symbols_are_rejected(self):
+        # Ungok case: dense short ticks at EL 5.624 and a few at -112.719 among 20-40 m contours.
+        doc=ezdxf.new();msp=doc.modelspace();self.contours(msp,[28,29,30,31,32,33])
+        for i in range(60):msp.add_lwpolyline([(40+2*i,20),(40+2*i,22)],dxfattribs={'elevation':5.624})
+        for i in range(4):msp.add_lwpolyline([(100+i,25),(100+i,27)],dxfattribs={'elevation':-112.719})
+        points,counts,_=read_survey_block(Path('unused.dxf'),self.options(),doc=doc)
+        self.assertEqual(counts['rejected_height_outliers'],64)
+        self.assertGreaterEqual(points[:,2].min(),28)
+
+    def test_real_peak_above_contours_is_kept(self):
+        doc=ezdxf.new();msp=doc.modelspace();self.contours(msp,[70,72,74,76,78,80])
+        msp.add_lwpolyline([(100,25),(100,27)],dxfattribs={'elevation':84})
+        points,counts,_=read_survey_block(Path('unused.dxf'),self.options(),doc=doc)
+        self.assertNotIn('rejected_height_outliers',counts);self.assertEqual(points[:,2].max(),84)
+
 if __name__=='__main__':unittest.main()