Journal of Geographic Information System, 2010, 2, 124-128
doi:10.4236/jgis.2010.22019 Published Online April 2010 (http://www.SciRP.org/journal/jgis)
Research on Data Sharing between AutoCAD and MapGIS
in Cadastral Database Construction
Jiajia Liu1, Yang Cai2
1Faculty of Information Engineering, China University of Geosciences, Wuhan, China
2Wuhan Zondy Cyber T
＆ S. Co. Ltd, Wuhan, China
Abstract
In the Second Chinese Country Survey, MAPGIS (Map Geographic Information System) is widely used all
over the country in the Cadastral Database Construction. There are plenty original data is saved in the Au-
toCAD (Auto Computer Aided Design) data format. Therefore it is important to find a way which can ex-
change and share the data between AutoCAD and MAPGIS effectively and efficiently. In order to use Map-
GIS cadastral management system building cadastral database, it researched the current transformation me-
thods between data of MapGIS and AutoCAD, including analysis defects of ObjectARX technology, south-
ern CASS conversion interface, DXF file conversion. Combining the characteristics of MAPSUV data and
southern CASS data, it found a data conversion method through the DWGdirectX control. This method ac-
tually read and wrote files provided by the library of MAPSUV and AutoCAD. This way avoids exchange
process which can better transform the southern CASS DWG file containing graphics and attributes informa-
tion to the SUV. The example which showed how DWG file transformed into SUV file. It improves the ef-
fectiveness and efficiency of conversion.
Keywords: Cadastral Database Construction, MapGIS, AutoCAD, Data Conversion, DWGdirectX
1. Introduction
Urban cadastral information system is an important sub-
system for land and resources information system [1].
MAPSUV is an urban cadastral information system pro-
viding a series of functions to build cadastral database
based on MapGIS. MapSUV has the same data format
with MapGIS. Southern CASS is based on AutoCAD
digital mapping system and cons ists with AutoCAD data
formats. It is widely used in data collection [2]. In order
to use MAPSUV to build cadastral database, it need to
transform DWG files to SUV files. We studied the pop-
ular ways of how data conversion between MAPSUV
and South CASS, then analyzed how to use DWGdirectX
to read DWG files, and finally gave an example of the
conversion between MAPSUV and South CASS.
2 Relevant Research on Data Conversion
AutoCAD and MapGIS have spatial coordinates, which
can link the target and reference system, describe the
topological relation data, and handle the graphics
attribute data. The major difference is that AutoCAD
data
mainly process regu lar geometry and its combination. Its
graphics functions, especially the 3d graphics functions
are powerful, while its attribute database functions is
relatively weak, which uses geometric coordinates. Map-
GIS mainly process natural target with complex fractal
characteristics, such as coastline, terrain contours, etc.
These graphics are difficult to process. MapGIS attribute
database contents structure is complex which has po-
werful functions. The conversion of graphics and
attribute are very flexible and professional [3]. MapGIS
usually uses geodetic coordinates, which has strong mul-
ti-level space analysis function. MapGIS has large
amount of data, diverse data input and professional data
analysis functions.
2.1. Based on ObjectARX Technology
ObjectARX is a development package for secondary
development on AutoCAD platform released by Auto-
Desk Company. It provides an object-oriented develop-
ment environment and application programming inter-

J. J. LIU ET AL. 125
face to access based on C++, which can quickly visits
graphics database of AutoCAD. The program of Objec-
tARX is a DLL, sharing the address space of AutoCAD,
which can directly use AutoCAD’s functions. DWG data
can be conveniently read through ObjectARX [4]. How-
ever, since the database developed by ObjectARX is ac-
tually dynamic, the second development module can
only be operat e d when AutoCAD is starte d .
2.2. Based on SOUTH CASS Interface
Southern CASS system provides two kinds of plain code
as data interface. One is CAS format file, which is sou-
thern CASS standard exchange format, which contains
all the graphics geometry and attributes information. The
data format is open, and stored in ASCII formats, which
can be read directly by read program. Another is QS
format ownership conversion file and it is also plain code
file which contains the parcel information of land cada-
stral. The file contains parcel NO., parcel name, land
classification, boundary point, and their coordinate, etc.
User can read parcel through this file. Due to the struc-
ture limitation, lots of information will be lost, such as,
when boundary line with arc is input in QS file, the arc
convexity info rmation will be lost.
2.3. Conversion File Based on DXF
DXF (Drawing Interchange Format) are widely used and
became a general rule. Through DXF file format, you
can use the high-level language development application
to read AutoCAD graphics files. User can also create
DXF file by AutoCAD. Through DXF file, the CASS
graphics data can be transformed. While when the DWG
file is stored in DXF file, all the attribute information
will be lost. DXF only support graph ic conversion, when
input DXF into MapGIS system all the attribute will be
lost. It will be the same when input MapGIS data into
DXF.
2.4. DWGdirectX Controls
DWGdirectX provides a series of API functions which
are powerful and convenient to operate DWG file format.
It can quickly visit variety entity and objects of Auto-
CAD and it shields version differences [5]. By using VB,
VC language, DWGdirectX can be independent of Au-
toCAD software environment, that is, user can read and
operate DWG file without open AUTOCAD software.
This component can read DWG file without in AUTO-
CAD application procedures.
3. Data Conversion Realization Based on
DWGdirectX ActiveX
3.1. Data Analysis of MAPSUV
The core of MapGIS data management is the operation
of work shop. In short, workshop is a data ruler which
is used to store spatial data, topological data, graphic
data and attribute data. Every workshop has a corres-
ponding MapGIS data file [6]. MAPSUV inherited
MapGIS workspace management data method. Ground
objects are the b asic un it for MAPSUV.
MAPSUV based on object-oriented ideas, uses sur-
veyed point to build ground objects method. The main
data object is as follows,
1) Surveying point, it’s the result of outdoor survey-
ing, which is also the base for constructing ground ob-
jects. Every surveying point has a corresponding point
on the earth. Besides basic 3D coordinates, these points
have attributes such as height and coding. The survey-
ing point structure is shown in Figure 1.
Each surveying point has a unique ID code to connect
ground objects. Th e point and its ID code should be put-
ted in the same file.
2) Ground object, it is a geological entity on the map
which is the symbols of real objects and it’s also the
outdoor surveying object. According to the ground ob-
jects type and shape, it can be divided into independent
ground objects (pole and lamp), linear objects (fence and
lamp), facet objects (lawn). If point, line and polygon are
taken as the basic geometric entity, then the ground ob-
jects are consisted by one or several entities. Ground
objects are corresponding to each one-by-one with geo-
logic entity, which can reflect the world more vividly.
The structure of one ground objects in SUV is as Figure 2.
3) Annotation, it’s the mark of ground objects. There
are two annotations in MapSUV, one is the attribute val-
ue of ground ob ject itself, which is marked automatically
by the system and can’t be deleted. The other one is
attribute which is written by user or selected marked
Name North Coordina te East Coordinat e Elevation Code Modeling Elevation Tootnote
Figure 1. Structure of surveying point.
Feature Name Location Information Connection Information Topographic Information Attribute Information

J. J. LIU ET AL. 126
Figure 2. Structure of feature in MAPSUV.
ground objects area, then mark the annotation manually
and the contents can be modified.
The SUV ground objects can be read in SUV ground
objects workshop. The workshop is the unit for MapGIS
point, line and polygon. Ground object is the data unit
for MapSUV. As for the annotation read and write in
SUV, all the annotation are processed in SUV ann otation
workshop.
3.2. Data Analysis of SOUTH CASS
Files in South CASS are stored in DWG format. Graphi-
cal information getting from CAD is stored in primitive
entity, such as reference block entity, single line entity,
circle entity and composite lien entity. Attribu te informa-
tion is stored in graphic entity expanding attribute. Ex-
panding data can store attribute encoding information
and a number of attribute information. In this way, ex-
panding attribute data could closely connect with graph-
ics which helps the integrated operation of graphic and
attribute and the data logic maintenance. Expanding data
in AutoCAD can be divided into several blocks by
APPNAME, so it is convenient to search. CASS use the
same way in attribute data storage. South CASS use
kinds of primitive entity of AutoCAD to express various
ground objects and annotation, that is, spatial data fea-
ture or graph ic type. It uses expanding d ata related entity
to express attribute feature.
3.3. Transformation Basic Idea
The conversion of DWG files into SUV files is simply as
follows, start DWGdirectX component in program to
obtain interface objects in AutoCAD service program
and gradually obtain AutoCAD model spatial interface
object. We can get expanding data which contain code of
CASS using spatial interface objects. Using code of
CASS, we can adjust a graphic element’s inter parame-
ters and know whether it contains attribute information
and attribute’s types, then through encoding reference
table to get corresponding SUV code. The entity inter-
face can be converted by the obtained primitive type to
get specific primitive entity such as, circular primitive
entity and composite line primitive entity. Different func-
tions can be extracted by different primitive entity and
then we can get geological information of ground object.
Finally we can convert the ground objects to SUV work-
shop by the functions provided by MapSUV secondary
development environment.
3.4. Prepare for Data Conversion
3.4.1. Organize the Encode Comparison table
In transforming process, we need a coding
cross-reference for CASS code and SUV code. The
ground object in CASS is much fewer than that in SUV,
therefore every CASS code has a corresponding code in
SUV. The reference table is saved as a text file named
CasToSuvCode.txt. The format in Figure 3 is as follows.
3.4.2. Organize the Symbols Define Table
The second step is to organize work.def file in CASS,
which divides all symbols into 21 groups. Symbols are
recorded in a unified form (shown in Figure 4) and
saved in work.def file. We should know the types of
landmark which are relative to CASS code. While orga-
nizing work.d ef file, we extract the information code and
type and save them in CASSWORK.DEF file in code
size.
3.5. Flow Chart of Transformation
4. Data Conversion Results
We can see how DWG files displayed in its South CASS
system in Figure 6, in which part of data are from Kun
Ming. In Figure 7, we can see the effect of DWG files
convert into SUV files.
From Figure 6 and Figure 7, we can see about 17000
landmark has been transformed and the conversion ac-
curacy rate achieves 99%. In the transform process, read
and write function actually provided by AutoCAD and
MAPSUV’s database which avoids the middle process of
file conversion. It’s more effective and has better conver-
sion effect.
CASS Code List Separator SUV Code List Separator Block Name
Figure 3. Code comparison table format.
CASS Code Symbol Layer Symbol Cate gory Parameter Parameter Symbol Remark

J. J. LIU ET AL. 127
Figure 4. Symbols define table format.
Figure 5. Transformation flow.

J. J. LIU ET AL. 128
Figure 6. Data in South CASS be for e transformation.
Figure 7. Data in MAPSUV after Transformation.
5. Conclusions
Both south CASS system and MAPSUV system are
widely used in building cadastral database. This paper
introduces a effective way to transform CASS’s data into
MAPSUV system. It has the following rules,
1) Convert DWG file of CASS to SUV file by
DWGdirectX component, which avoids data loss of CAS
file and QS file due to inherent structure. DWGdirectX
can directly get data conversion data of the secondary
development database provided by DWG of AutoCAD.
In this way, data can be converted to SUV more accurate
and the efficiency can be improved.
2) Because both CASS and MAPSUV obey general
standards in building cadastre database, they have the
same way to draw landmark. The most important parcel
information in building cadastre database is same. Al-
though a number of data might be lost, the data still
meets the standards.
6. References
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J. J. LIU ET AL. 129
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