Science in China Series D: Earth Sciences
© 2007 SCIENCE IN CHINA PRESS
Springer
www.scichina.com www.springerlink.com Sci China Ser D-Earth Sci | June 2007 | vol. 50 | Supp. I | 169-175
An equal area conversion model for rasterization of
vector polygons
ZHOU ChengHu
1†
, OU Yang
1
, YANG Liao
2
& QIN Biao
3
1
State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences, and Natural Re-
sources Research, Chinese Academy of Sciences, Beijing 100101, China;
2
Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Ürümqi 830011, China;
3
Mathematics Department of Xi’an Transportation University, Xi’an 710009, China
Vector-raster conversion is one of the classic research topics in the field of Geographical Information
Systems (GIS). The algorithms commonly used in GIS are devoted to maintaining the vector polygons'
shape characteristics, but neglect the gain and loss of a polygon’s area, which is another important
attribute. This paper proposes an equal-area conversion model based on an area compensation opti-
mization principle. According to the topological relationship among polygons and boundary grids, a
neighborhood compensation principle was adopted to assign the attributes of boundary grids and a
global optimization algorithm was developed to minimize area distortion in the whole data set. Two
experiments were designed and the results indicated that this algorithm not only guaranteed the area
error is as small as possible, but also has the advantage as being adaptive to polygon shape and spa-
tial structure.
vector polygon, vector-raster conversion, boundary grid, area distortion, boundary geometric characteristics
1 Introduction
The vector and raster are the most basic data models
used to express spatial data
[1]
in GIS. Along with the
development of modern spatial information gathering
technologies such as remote sensing and global posi-
tioning systems, grid-format data has become the domi-
nant data source in the area of GIS. Grid data processing,
storage, analysis and application has also focused atten-
tion on GIS once more
[2,3]
. In classical GISs, the vec-
tor-raster conversion has been intensively researched
and all commercial GIS software systems provide a
conversion module as a basic function. The key points of
this conversion are fast determination of boundary unit
cells (called boundary grids), and assignment of the
boundary grid’s attributes. For the determination of
boundary grids, the methods of covering the mem-
brane
[4]
, boundary algebra polygon packing
[5]
, boundary
pursuit
[6]
, broken line boundary pursuit
[7]
, and others,
were established. The boundary algebra algorithm is the
most simple, reliable and least time-consuming of the
above methods
[5]
. The attribute of a boundary grid can
be determined by the principles of superior area, supe-
rior perimeter, the central point, or the importance of the
cell. And superior area principle is most adopted
[8]
.
The transformation of vector polygons to raster grids
is a process that results in losses. It involves changes to
the area and perimeter of a polygon and the distortion of
the shape and topology, along with other alterations
[9]
.
Therefore, it is understandable that different vec-
tor-raster conversion methods produce different trans-
formation results because they employ different princi-
ples
[8]
. Much research has been devoted to the analysis
Received September 26, 2006; accepted February 10, 2007
doi: 10.1007/s11430-007-5013-6
†
Corresponding author (email: zhouch@lreis.ac.cn)
Supported by the Knowledge Innovation Project of Chinese Academy of Sciences
(No.KZCX3-SW-347),and the National Science Fund for Distinguished Young
Scholars (Grant No. 40225004)