diff --git a/Localization/histogram_filter/histogram_filter.py b/Localization/histogram_filter/histogram_filter.py
index 95b15426..4de8df8a 100644
--- a/Localization/histogram_filter/histogram_filter.py
+++ b/Localization/histogram_filter/histogram_filter.py
@@ -12,44 +12,55 @@ import matplotlib.pyplot as plt
 from scipy.stats import norm
 
 EXTEND_AREA = 10.0  # [m] grid map extention length
+SIM_TIME = 50.0  # simulation time [s]
+DT = 0.1  # time tick [s]
+MAX_RANGE = 10.0  # maximum observation range
 
 show_animation = True
 
 
-def generate_gaussian_grid_map(ox, oy, xyreso, std):
+def observation_update(gmap, z, std, xyreso, minx, miny):
 
-    minx, miny, maxx, maxy, xw, yw = calc_grid_map_config(ox, oy, xyreso)
+    for iz in range(z.shape[0]):
+        for ix in range(len(gmap)):
+            for iy in range(len(gmap[ix])):
 
-    gmap = [[0.0 for i in range(yw)] for i in range(xw)]
+                zr = z[iz, 0]
+                x = ix * xyreso + minx
+                y = iy * xyreso + miny
 
-    for ix in range(xw):
-        for iy in range(yw):
+                d = math.sqrt((x - z[iz, 1])**2 + (y - z[iz, 2])**2)
 
-            x = ix * xyreso + minx
-            y = iy * xyreso + miny
+                pdf = (1.0 - norm.cdf(abs(d - zr), 0.0, std))
+                gmap[ix][iy] *= pdf
 
-            # Search minimum distance
-            mindis = float("inf")
-            for (iox, ioy) in zip(ox, oy):
-                d = math.sqrt((iox - x)**2 + (ioy - y)**2)
-                if mindis >= d:
-                    mindis = d
+    gmap = normalize_probability(gmap)
 
-            pdf = (1.0 - norm.cdf(mindis, 0.0, std))
-            gmap[ix][iy] = pdf
-
-    return gmap, minx, maxx, miny, maxy
+    return gmap
 
 
-def calc_grid_map_config(ox, oy, xyreso):
-    minx = round(min(ox) - EXTEND_AREA / 2.0)
-    miny = round(min(oy) - EXTEND_AREA / 2.0)
-    maxx = round(max(ox) + EXTEND_AREA / 2.0)
-    maxy = round(max(oy) + EXTEND_AREA / 2.0)
-    xw = int(round((maxx - minx) / xyreso))
-    yw = int(round((maxy - miny) / xyreso))
+def calc_input():
+    v = 1.0  # [m/s]
+    yawrate = 0.1  # [rad/s]
+    u = np.matrix([v, yawrate]).T
+    return u
 
-    return minx, miny, maxx, maxy, xw, yw
+
+def motion_model(x, u):
+
+    F = np.matrix([[1.0, 0, 0, 0],
+                   [0, 1.0, 0, 0],
+                   [0, 0, 1.0, 0],
+                   [0, 0, 0, 0]])
+
+    B = np.matrix([[DT * math.cos(x[2, 0]), 0],
+                   [DT * math.sin(x[2, 0]), 0],
+                   [0.0, DT],
+                   [1.0, 0.0]])
+
+    x = F * x + B * u
+
+    return x
 
 
 def draw_heatmap(data, minx, maxx, miny, maxy, xyreso):
@@ -59,24 +70,91 @@ def draw_heatmap(data, minx, maxx, miny, maxy, xyreso):
     plt.axis("equal")
 
 
+def observation(xTrue, u, RFID):
+
+    xTrue = motion_model(xTrue, u)
+
+    # add noise to gps x-y
+    z = np.matrix(np.zeros((0, 3)))
+
+    for i in range(len(RFID[:, 0])):
+
+        dx = xTrue[0, 0] - RFID[i, 0]
+        dy = xTrue[1, 0] - RFID[i, 1]
+        d = math.sqrt(dx**2 + dy**2)
+        if d <= MAX_RANGE:
+            dn = d
+            zi = np.matrix([dn, RFID[i, 0], RFID[i, 1]])
+            z = np.vstack((z, zi))
+
+    return xTrue, z
+
+
+def normalize_probability(gmap):
+
+    sump = sum([sum(igmap) for igmap in gmap])
+    #  print(sump)
+
+    for i in range(len(gmap)):
+        for ii in range(len(gmap[i])):
+            gmap[i][ii] /= sump
+
+    return gmap
+
+
+def init_gmap(xyreso):
+
+    minx = -15.0
+    miny = -5.0
+    maxx = 15.0
+    maxy = 25.0
+    xw = int(round((maxx - minx) / xyreso))
+    yw = int(round((maxy - miny) / xyreso))
+
+    gmap = [[1.0 for i in range(yw)] for i in range(xw)]
+    gmap = normalize_probability(gmap)
+
+    return gmap, minx, maxx, miny, maxy,
+
+
 def main():
     print(__file__ + " start!!")
 
     xyreso = 0.5  # xy grid resolution
-    STD = 5.0  # standard diviation for gaussian distribution
+    STD = 1.0  # standard diviation for gaussian distribution
 
-    for i in range(5):
-        ox = (np.random.rand(4) - 0.5) * 10.0
-        oy = (np.random.rand(4) - 0.5) * 10.0
-        gmap, minx, maxx, miny, maxy = generate_gaussian_grid_map(
-            ox, oy, xyreso, STD)
+    # RFID positions [x, y]
+    RFID = np.array([[10.0, 0.0],
+                     [10.0, 10.0],
+                     [0.0, 15.0],
+                     [-5.0, 20.0]])
+
+    time = 0.0
+
+    xTrue = np.matrix(np.zeros((4, 1)))
+
+    gmap, minx, maxx, miny, maxy = init_gmap(xyreso)
+
+    while SIM_TIME >= time:
+        time += DT
+
+        u = calc_input()
+        xTrue, z = observation(xTrue, u, RFID)
+
+        gmap = observation_update(gmap, z, STD, xyreso, minx, miny)
 
         if show_animation:
             plt.cla()
             draw_heatmap(gmap, minx, maxx, miny, maxy, xyreso)
-            plt.plot(ox, oy, "xr")
-            plt.plot(0.0, 0.0, "ob")
-            plt.pause(1.0)
+            plt.plot(xTrue[0, :], xTrue[1, :], "xr")
+            plt.plot(RFID[:, 0], RFID[:, 1], ".k")
+            for i in range(z.shape[0]):
+                plt.plot([xTrue[0, :], z[i, 1]], [
+                         xTrue[1, :], z[i, 2]], "-k")
+            plt.title("Time[s]:" + str(time)[0: 4])
+            plt.pause(0.1)
+
+    print("Done")
 
 
 if __name__ == '__main__':