The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
flight lines. The spots surveyed by GPS are showed with the 
numbers with red color and little points. The area is about 10 
square kilometers. The flight and footprints information are: 
• flight height above ground: 800 meters; 
• flight speed: 160 kilometers per hour; 
• flight direction: from west to east and from east to west; 
• the number of flight lines: 12; 
• Pulse Repetition Frequency (PRF): lOOKHz; 
• Scan angle: 20 degree; 
• The overlap of two conjoint swath: 44%; 
• The mean distance of footprints: 0.51 meters; 
• Distance from GPS base station to study area: 130 
kilometers. 
3. WHAT DID WE DO AND DISCUSSION 
3.1 Accuracy of elevation of LiDAR data 
We processed the LiDAR data with TerraSolid Software: 
TerraScan, TerraPhoto, and TerraModeler. The DEM and DSM 
data can be done with TerraScan and TerraModeler, and DOM 
need TerraScan and TerraPhoto. We also made 
three-dimensional models with TerraScan, TerraPhoto. Making 
DLG is more complicated, that need other soft and skills 
besides TerraSolid Software. 
The precision of DEM is the most important to LiDAR system. 
We acquired points’ XYZ with GPS in the site before the flight, 
then import to TerraScan soft. It can be got following result: 
3Ì.13 
. 
31.2:3 
31.16 
Figure 3 Differences between 1:500 and 1:1000 DLG 
The elements in 1:1000 scale DLG was draw in black, which 
were made in TerraSolid software with LiDAR point clouds 
and images. In comparison, 1:500 scale was done in field 
survey with Total Stations drawing in red color. From black 
circles in figure 3 we can see 1:1000 scale map is deviate to 
east. But, the distance is less than 0.8 meters, and it is systemic. 
In black rectangle of figure 3, elevation values are almost same 
that proved elevation accuracy very good. 
F: !£ELIDAR3&ffiiJ&S\JIANCE.txt 
Number 
Easting 
Northing 
Known Z 
Laser Z 
Dz 
ldl 
130404.695 
141396.610 
13.481 
13.580 
+0.099 
Id 2 
130583.982 
141141.073 
21.471 
21.560 
+0.089 
ld3 
129479.590 
140676.407 
25.338 
25.330 
-0.008 
ld4 
130206.297 
140877.628 
26.185 
26.240 
+0.055 
ld6 
130091.842 
140493.284 
20.818 
20.900 
+0.082 
ld8 
130742.662 
140383.073 
16.641 
16.620 
-0.021 
ldlO 
129907.651 
140065.637 
18.509 
18.390 
-0.119 
ldl 2 
129363.992 
141286.615 
32.422 
32.490 
+0.068 
ldl3 
129174.019 
141103.580 
32.138 
32.130 
-0.008 
ldl 6 
128673.826 
140009.613 
32.409 
32.560 
+0.151 
ldl8 
128668.458 
141326.461 
41.379 
41.480 
+0.101 
ldl9 
127558.540 
141322.459 
27.658 
27.670 
+0.012 
ld22 
127685.330 
139354.422 
36.031 
36.090 
+0.059 
ld23 
127586.736 
138688.504 
24.400 
24.410 
+0.010 
ld25 
130870.793 
139836.037 
12.122 
12.180 
+0.058 
ld26 
129426.492 
139102.398 
23.945 
23.910 
-0.035 
ld28 
127487.616 
140337.378 
66.046 
55.890 
-0.156 
ld29 
127879.356 
140594.842 
55.038 
55.140 
+0.102 
ld31 
128237.660 
139726.818 
41.783 
41.400 
-0.383 
Average dz 
+0.008 
Minimum dz 
-0.383 
Maximum dz 
+0.151 
Average magnitude 
0.085 
Root mean square 
0.119 
Std deviation 
0.122 
Figure 2 Deviations of ground footprints to GPS points 
There are 19 points we have got coordinate. We found that 
average dz is 0.008 meter, root mean square is 0.119 meter, and 
standard deviation is 0.122 meter. The accuracy of elevation is 
every good. 
3.2 Accuracy of DLG by LiDAR data 
After processing point clouds of LiDAR data, we according 
images obtained by camera of ALTM3100 system, drew one sq. 
kilometer topographical map at 1:1000 scale in 4 sheets. The 
maps from LiDAR system were contrasted with the map at 
1:500 scales from field surveying. Following figure 3 showed 
there are small offset between two kinds of maps, except for 
some edges of small road line in front of houses. 
3.3 Accuracy of DOM and three-dimensional models by 
LiDAR 
DOM can be done with the images of digital camera, such as 
ADS40, DMC and UCX. It also can be done with the images of 
camera installed along laser scanner in LiDAR system. We 
have done 10 sq. km DOM in Nanjing and check its accuracy 
with two types of methods, which are based GPS and DLG 
survey. The following figure shows how to add 1:500 scale 
DLG onto DOM. 
Figure 4 contrast of DLG and DOM 
The figure 4 showed DLG and DOM were matched well. There 
is small deviation on two type of map. If we consider DLG 
have high accuracy, the DOM have a systemic error according 
showing of figure 4, which is 0.8 meter with west to east 
direction. 
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