diff --git a/exp/board_detect.py b/exp/board_detect.py
--- a/exp/board_detect.py
+++ b/exp/board_detect.py
@@ -13,7 +13,6 @@ import scipy.cluster
 import scipy.ndimage
 import scipy.signal
 
-from geometry import Line
 from polar_hough import PolarHough
 from annotations import DataFile,computeBoundingBox
 from hough import show,prepareEdgeImg,HoughTransform
@@ -73,21 +72,6 @@ def filterStones(contours,bwImg,stoneDim
 	return res
 
 
-def groupLines(points,minCount,tolerance):
-	random.shuffle(points)
-	sample=points[:]
-	for (i,a) in enumerate(sample):
-		for (j,b) in enumerate(sample):
-			if j<=i: continue
-			ab=Line(a,b)
-			for c in points:
-				if c is a or c is b: continue
-				if point2lineDistance(a,b,c)<=tolerance:
-					ab.points.add(c)
-			if len(ab.points)>=minCount:
-				yield ab
-
-
 class BoardDetector:
 	def __init__(self,annotationsPath):
 		self._annotations=DataFile(annotationsPath)
@@ -130,9 +114,6 @@ class BoardDetector:
 		hough.update(stonesImg,5)
 		hough.extract()
 
-		# # detect lines passing through the stones
-		# lines=self._constructLines(stones)
-		#
 		# # detect vanishing points of the lines
 		# imgCenter=EPoint(w//2-x1, h//2-y1)
 		# (a,b,c,d)=(p-EPoint(x1,y1) for p in self._annotations[filename][0])
@@ -191,44 +172,6 @@ class BoardDetector:
 		show(stones,"black and white areas")
 		return stones
 
-	def _constructLines(self,stoneLocs):
-		lineDict=dict()
-		# minCount=min(max(math.sqrt(len(stoneLocs))-4,3),7)
-		minCount=6
-		log.debug("min count: %s",minCount)
-		points=[point for (point,contour) in stoneLocs]
-		for line in groupLines(points,minCount,2):
-			key=line.getSortedPoints()
-			if key in lineDict: # we already have a line with the same incident points
-				continue
-			lineDict[line.getSortedPoints()]=line
-			obsolete=set()
-			for ab in lineDict.values():
-				if ab is line: continue
-				if line.points<ab.points: # == impossible
-					del lineDict[key]
-					break
-				if ab.points<line.points:
-					obsolete.add(ab.getSortedPoints())
-			for key in obsolete: del lineDict[key]
-		log.debug("valid lines: %s",len(lineDict))
-		lines=sorted(lineDict.values(), key=lambda ab: len(ab.points), reverse=True)
-
-		# visualize
-		linesImg=cv.cvtColor(np.zeros((self._rectH,self._rectW),np.uint8),cv.COLOR_GRAY2BGR)
-		cv.drawContours(linesImg,[c for (point,c) in stoneLocs],-1,(255,255,255),-1)
-		for (p,c) in stoneLocs:
-			cv.drawMarker(linesImg,(int(p.x),int(p.y)),(255,0,0),cv.MARKER_CROSS)
-		self._printLines(lines,points,linesImg)
-		for line in lines:
-			points=line.getSortedPoints()
-			(xa,ya)=points[0]
-			(xb,yb)=points[-1]
-			cv.line(linesImg,(int(xa),int(ya)),(int(xb),int(yb)),(255,255,0),1)
-		show(linesImg)
-
-		return lines
-
 	def _printLines(self,lines,allPoints,img):
 		for (i,line) in enumerate(lines):
 			img_=np.copy(img)