As for the observed height, good results were obtained in the test 
file. When the ground control point No. 1 is concerned, only one 
point on line A is reflected and five points on line E were 
reflected. As long as the repeatability of height is concerned and 
all the lines are taken into consideration, 20cm variation and the 
standard deviation of 0.1 lm can be seen. This variation may be 
occurred due to the divergence of laser at the object and also due 
to the reflection at the edge of ground control point. The deviation 
from the mean height of each control point is shown in Fig 3. The 
standard deviation of 0.09m, which is due to the errors of GPS 
and laser, is called the accuracy of the repeatability of height. 
Comparison of GPS and profiling: Following tables are the 
result of comparison between coordinates by laser profiling and 
coordinates by GPS-leveling. And we estimated the accuracy 
quantitatively in each survey line. GPS survey was carried out for 
one hour in static mode on each ground control point. As for laser 
profiling, the horizontal coordinates of the peak of contours were 
assigned to the ground control point which is located 80cm above 
the ground. The mean height shown in the previous tables were 
regarded as orthometric heights. 
Table 4 Comparison of GPS and laser profiling 
Ground control point 1 
Fine 
XYH 
GPS 
Profiling 
Res. 
Dist. 
X 
15604.265 
15604.10 
-0.17 
0.32 
A 
Y 
24064.631 
24064.90 
0.27 
H 
11.808(GPS) 
11.92 
0.11 
X 
15604.265 
15604.18 
-0.09 
0.26 
C 
Y 
24064.631 
24064.39 
-0.24 
H 
11.808(GPS) 
11.90 
0.09 
X 
15604.265 
15603.87 
-0.40 
0.51 
E 
Y 
24064.631 
24064.32 
-0.31 
H 
11.808(GPS) 
11.85 
0.04 
Ground control point 2 
Line 
XYH 
GPS 
Profiling 
Res. 
Dist. 
X 
15420.563 
15420.43 
-0.13 
0.33 
D 
Y 
24280.727 
24280.43 
-0.30 
H 
11.689(GPS) 
11.73 
0.04 
X 
15420.563 
15419.72 
-0.84 
0.84 
E 
Y 
24280.727 
24280.79 
0.06 
H 
11.689(GPS) 
11.88 
0.19 
Ground control point 3 
Line 
XYH 
GPS 
Profiling 
Res. 
Dist. 
X 
15177.590 
15177.18 
-0.41 
0.65 
Y 
24105.950 
24105.44 
-0.51 
l 
H 
11.810(GPS) 
11.90 
0.09 
FT 
11.694(level) 
11.90 
0.21 
X 
15177.590 
15177.35 
-0.24 
0.27 
D 
Y 
24105.950 
24105.83 
-0.12 
H 
11.810(GPS) 
11.88 
0.07 
H’ 
11.694(level) 
11.88 
0.19 
Ground control point 4 
Line 
XYH 
GPS 
Profiling 
Res. 
Dist. 
A 
X 
15326.239 
15326.50 
0.26 
0.51 
Y 
23892.333 
23891.89 
-0.44 
H 
11.849(GPS) 
11.94 
0.09 
H’ 
11.737(level) 
11.94 
0.20 
G 
X 
15326.239 
15325.95 
-0.29 
0.31 
Y 
23892.333 
238892.43 
0.10 
H 
11.849(GPS) 
11.73 
-0.12 
H’ 
11.737(level) 
11.73 
-0.01 
Ground control point 5 
Line 
XYH 
GPS 
Profiling 
Res. 
Dist. 
X 
15400.794 
15400.48 
-0.31 
0.31 
C 
Y 
24119.504 
24119.45 
-0.05 
H 
10.587(GPS) 
10.69 
0.10 
X 
15400.794 
15400.54 
-0.25 
0.25 
B 
Y 
24119.504 
24119.53 
0.03 
H 
10.587(GPS) 
10.70 
0.11 
X 
15400.794 
15400.20 
-0.59 
0.59 
F 
Y 
24119.504 
24119.57 
0.07 
H 
10.587(GPS) 
10.71 
0.12 
The average of distance difference between GPS survey and 
profiling was 0.40m with the standard deviation of 0.17m. When 
the laser profiling is concerned, as for ground control point No.4, 
X of survey line A is 15326.50 and X of survey line G is 
15325.95. Thus the residual is 0.55m. that is, the accuracy of