Nanjing Institute of Surveying Mapping & Geotechnical Investigation, Co. Ltd.
8 WangFu Avenue Xinjiekou Square Nanjing 210005, P. R. China - cspringhwq@yahoo.com.cn.
KEY WORDS: LiDAR, Surveying, Analysis, DEM/DTM, Accuracy, Test
ABSTRACT:
There are over 10 sets of LiDAR system into China until end of 2007, but they did not in full of working. One reason is big capacity
of the market need a long period time. Another is author of this article concerned that is accuracy of LiDAR data when it does
surveying projects. In this article, the author make the analyze accuracy of LiDAR data base study site in Nanjing, China. All of them
are from point of view productions of surveying and mapping. Last, the author make conclusion: LiDAR data acquiring is important
and accuracy of LiDAR data is good, especially accuracy of DEM/DSM productions is very well.
1. INTRODUCTION
1.1 LiDAR technology developing is faster than before in
China
Nowadays, LiDAR (Light Detecting And Ranging) is more and
more frequent used in all kinds of fields, such as forest
measurement, transportation and power transmission fields. A
lot of enterprises want introduce LiDAR systems and software
into China from abroad, which are close related surveying and
mapping field. Until end of 2007 year, there are over 10 sets of
LiDAR systems coming into China and extending surveying
and mapping market. They are nearly including all kinds of
type of LiDAR systems by commercial vendors: Optech, Leica,
LitterMapper, Riegl, and TopoSys. The first commercial
LiDAR system came into China in 2004. It is a quite big
problem how to put them in full working, because big capacity
of the market need a long period time.
1.2 The feature of LiDAR data
Airborne LiDAR data is including point clouds and images.
Point clouds have horizontal and vertical positional information
and intensity. Images are acquire if laser scanner with a digital
camera. We can make DEM/DSM (Digital elevation Model or
Digital Surface Model), DOM (Digital Orthoimages Mapping),
DLG (Digital Line Mapping) and three-Dimensional Models
(3DM) with LiDAR system. In survey and mapping field,
LiDAR data have several benefits: first, it can get precise
elevation of ground, trees and buildings, which can only be
obtained by conventional aerial photography method before.
Moreover, LiDAR method has more accurate than it. Second,
points and images of LiDAR systems can be used to build
three- dimensional models without current topographical map.
This broke up current circle procedure of making
three-dimensional models.
1.3 Accuracy of LiDAR data
In China, because the LiDAR system and main interrelated
technique came from foreign country recent year, users do not
really grip how much the deviations to practical value will be
occurred if use LiDAR system doing projects, as well as how to
control them. Morsdorf et al. [2004] and Lukas Wotruba[2005]
put 4 cardboard covered tables at comer of study site to
compute the planimetrie offsets, height offset and height
variations of the raw laser data. They make a perfect test on
characters of raw laser data, but few people give a good
comparison of four-D (DEM, DOM, DLG, and DM) production
from two kinds of data source and methods: photogrammetry
and LiDAR. This article will describe accuracy of LiDAR data
from point of view production of it.
2. STUDY AREA
LiDAR data were collected over the study area in March, 2006
with an ALTM3100 Optech system mounted on a fixed wings
airplane platform by Nanjing Institute of Surveying Mapping &
Geotechnical Investigation, Co. Ltd. There are one small hill
and several roads with many buildings standing on two of sides.
The site is near downtown of Nanjing, Jiangsu province of
China. Following picture (figure 1) will show the details of the
study area.
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