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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part B4. Beijing 2008 
LiDAR technology is one kind of high technology integration 
system, which can explore objects and measure distance by the 
way of laser scanning. With this system we can obtain urban 
data surface model easily. How to build 3D models of digital 
city is a big issue to discuss by professional people. Working 
with point clouds of LiDAR data and images is good method, 
which only need point clouds. So, we build over 1000 buildings 
and some bridges with LiDAR data in Nanjing. Following 
figure 5 showed footprints and three-dimensional models. 
Figure 5 LiDAR footprints display on three-dimensional 
models 
We can make three-dimensional models according points and 
images. The cloud points can make more perfect description on 
proof of building than others. We also analyze accuracy of them. 
We found that the error of elevation is smaller than 0.5 meters 
and it can describe surface of top of buildings. 
3.4 More research work we did 
Another part of research work is field survey with GPS and 
Total Stations. We want to know how much deviation of 
LiDAR points in DEM. We selected 4 lines with 0.6KA/L 
1.0KA/L 0.7KM and 1.1 KM long, and they are on the asphalt of 
the road surface. The footprints are all on break line, so we can 
distinguish them between others. On the other hand, we got the 
coordination of these points with GPS, and then contrasted with 
them. We also survey 45 transects of the road with GPS, and 
made other contrast to find how much differences they had. 
Figure 6 break lines survey in two ways 
This figure 6 is divided into three parts: left, middle, and right. 
The left show the all concerned site and the middle is the 
details in black circle in the left. The right is same site as the 
middle but in shadowed feature of LiDAR data. They have 
same points that were connected by light lines and showing 
with small black or white circles. From our research it can be 
found that we can obtain break lines with LiDAR data, but it is 
dependent on the density of footprints. In other words, if the 
mean distance of two LiDAR points is bigger than one meter, 
acquiring ordinary break lines will be more difficult. From 
comparison between 45 transects of the road with GPS and 
obtained with LiDAR data, we conclude that there is no much 
different in them, and we can do transects of the road with 
LiDAR systems instead of field survey. 
4. CONCLUSIONS 
From our research work, we have got followed conclusion on 
accuracy of LiDAR data: 
1, It is important that LiDAR data acquiring. Stabilization of 
flight is also important. It is the most important factor to affect 
accuracy of post processing. 
2, Accuracy of DEM is very good, mean error is smaller than 
0.15 meters in elevation value. It can be used in design projects 
of transportation and all kinds of survey projects. 
3, Accuracy of DOM is good, mean error is smaller than 1 
meter planar value. It can be used in almost survey projects and 
3 dimensional model building projects. 
4, Accuracy of DLG is OK, mean error of plane smaller than 1 
meter. It can be used in drawing under 1:2000 scales 
topographic. 
5, it is one of the best ways to found 3D models of digital city 
with data of LiDAR system. 
REFERENCES 
Arttu Soininen, 1998-2004. Manual for four modules of 
Terrasolid software. Terrasolid Inc, Finland. 
Gary C. Guenther, A. Grant Cunngham, Paul E. Larocque, and 
David J., 2000. The accuracy challenge in airborne LiDAR 
bathymetry. Proceedings of EARSel-SIG-workshop LiDAR, 
Dresden/FRG. pp 16-17. 
Han Wenquan, et al. 2007, Analysis of workflow of 
producing DLG with LiDAR technology, bulletin of surveying 
and mapping, No.5 (sum. 362), pp58-60. 
Lukas Wotruba, et al. 2005, assessment of sensor 
characteristics of an airborne laser scanner using geometric 
reference targets, ISPRS WG III/3, III/4, V/3 Workshop "Laser 
scanning 2005", Enschede, the Netherlands, September 12-14. 
Wang Xiaohui, et al. 2007, precision tests LiDAR data products. 
Engineering of surveying and mapping. pp67-69. 
Zhang dong, 2005, Wu Han University. Based on the LIDAR 
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urban housing. pp8-17. 
ACKNOWLEDGEMENTS 
This work was supported in part by National 863 plans projects: 
software platform of processing LiDAR data. Project No. is 
2006AA12Z101.