15 
irt B4. Beijing 2008 
a great deal of labor 
: burden on workers 
)rking hours for the 
/ironment requires 
lecifications, spatial 
ual work. It is also 
his work. Therefore, 
r stem in which the 
as automated as 
build a production 
h consideration has 
ngineers. 
A WATERMARKING ALGORITHM FOR VECTOR GEO-SPATIAL DATA BASED ON 
INTEGER WAVELET TRANSFORM 
Chang-qing ZHU ab , Cheng-song YANG b ,Qi-Sheng Wang b ’ c 
“Ministry of Education Key Laboratory of VGE, Nanjing Normal University, Nanjing 210054 - 
ycsdongshang@ 163 .com 
b Institute of Surveying and Mapping, Information Engineering University, Zhengzhou 450052 - 
zcq88@263.net 
‘"Surveying and Mapping Support Unit of South Xinjiang, Shule, Xinjiang 844200 - 
qishengw@yahoo.cn 
Commission VI, WG IV/1 
and Infrastructure KEY WORDS: Digital Watermarking, Vector Geo-Spatial Data, Integer Wavelet Transform, Robust 
for Geographic 
ABSTRACT: 
Considering the characteristic of vector geo-spatial data for digital watermarking, this paper presents a new watermarking algorithm 
for vector geo-spatial data based on integer wavelet transform. By the proposed algorithm, the line and surface coordinate points are 
decomposed by integer wavelet transform firstly, then watermark is embedded in the low frequency coefficients of integer wavelet 
transform, and the vector geo-spatial data with watermark is obtained by inverse integer wavelet transform finally. The experiments 
show that the proposed algorithm can effectively resist the attack of noise, data compressing, points deleting and format exchanging. 
For integer vector geo-spatial data, the algorithm can restitute the data well. 
1 INTRODUCTION 
Geo-spatial data are the supporting production of national 
infrastructure and geoscience’s research; it plays a significant 
role in the national economy and defense construction. The 
security of geo-spatial data refers to national security, 
technology cooperation and copyright protection. At present, 
there must have a credible technology to secure the security of 
geo-spatial data. 
The digital watermarking is a new developed former technology 
of information security (Sun Shenghe, 2004, Yang Yixian, 2006). 
There have been many applications for digital watermarking in 
many fields such as digital images, video, audio and so on. For 
vector geo-spatial data there were a few studies on the digital 
watermarking. A watermarking algorithm based on disperse 
cosine transform was proposed for vector geo-spatial data (M 
Voigt, 2004). A vector geo-spatial data watermarking algorithm 
by disperse Fourier transform is developed(V. 
Solachidis,2000).A watermarking algorithm that plotted out a 
map to many blocks and embedded watermark to the vertex 
coordinates of sub-block is proposed. A watermarking algorithm 
to resist compressing attack was proposed (ZHU 
Chang-qing,2006). A blind watermarking method based on 
wavelet transform was developed for vector map(Li 
Yuanyuan,2004). 
For these studies, the results from the algorithms based on 
transform domain are mainly floating. So when embedding 
watermark, the precision for integer data will reduce more or 
less. The lost will influence detecting watermark and make it 
hard to building the digital watermarking algorithm from which 
vector geo-spatial data can be restituted well. Considering the 
essential characteristic of vector geo-spatial data and the new 
wavelet technology, the paper studies the digital watermarking 
algorithm for vector geo-spatial data based on integer wavelet 
transform. 
Lifting scheme, based on spatial domain, is said to be the key 
technology for constructing secondary wavelet. Because lifting 
scheme does not depend on translation, and not need spectrum 
analysis tools, it can be used in constructing wavelet on finite 
area, surface and non-uniform sampling data and so on. Based 
on lifting scheme, the integer data set can also be integer data 
set when transforming by wavelet transform. Because the 
transform coefficients do not need quantize, there is fast 
algorithm by addition and shift operation and no quantization 
error in the watermarking algorithm based on integer wavelet 
transform. The characteristic of Multi-scale in integer wavelet 
transform which matches the visual characteristic is good for 
imperceptibility of watermark. Because the coefficients of 
integer wavelet transform have physics meaning, the embedding 
and detecting of digital watermark can be convenient. 
In general, the vector geo-spatial data is stored to files with the 
layered form. And contour is a basic and important layer data in 
vector geo-spatial data. Hence, in the paper, contour is used as 
the example of vector geo-spatial data. As all known, contour 
data is composed of the data with position and attribute 
information. Because attribute data cannot be changed 
unbending in general, the watermark is embedded in position 
data of contour in the paper. 
A line and surface elements of position data in the vector 
geo-spatial data are composed of a series of points with 
coordinate X and y . If the number of points for a line or surface 
elements is N , the line or surface elements can be represented 
as z(ri) = x{n) + i■ y(n) > n = 0,1,...,N-\ ■ For a line or surface 
elements, because of the high relativity between the 
neighborhood points, integer wavelet transform is used to the 
coordinates of points, and the watermark is embedded into the 
transform coefficients.