f 
= 
a 
Ta 
o s« ® 
etc. 
Arc Length Calculation 
In GIS besides the above mentioned area calcula- 
tion, it's usually needed to calculate the length of the 
linear ground objects such as roads, rivers and coast 
lines, etc. The process of length calculation is just like 
that of the area calculation of polygons. The first thing 
to do is also the arc attribute inputing, the inputing 
methods of arc attrbiute and polygon attribute are the 
same. After attribute inputing is finished, they also 
need to do attribute checking up and modifying. The 
only difference is that the arc attribute include line 
width. Finally the arc length statistics can be carried 
out according to its attribute value. 
Database Management 
In order to manage the land information, we devel- 
oped a database management system using C language in 
this software system. Its main characteristics is that the 
database setting up, database editing, modifing and up- 
dating all adopted the full screen interactive input and 
editing pattern. It is very convenient to use. Addtional- 
ly the speeds of making inquiry and statistics are very 
fast. The interface of the management system is very 
good, and the functions of the system are powerful, its 
main functions are as follows: 
* the full screen interactive input of data 
* data adding, deleting and modifying (adopting 
the full screen interactive editing pattern) 
* data inquirying 
* data display and print 
* automatic data statistics 
* automatic generating of statistical table. 
DOS Command Calling 
This software package has a good user interface, 
all functions of the system can be called directly from 
the menu, besides that the software system can directly 
call all DOS commands, all kinds of compilers and edit- 
ing software, even it can be directly call the application 
softwares such as AutoCAD and Paintbrush. So it pro- 
vide very good using and developing enviroments for 
customer, and good interface for users . At the same 
LU 
time it can greatly enrich the functions of the system. 
EXPERIMENT 
Now this software system is successfully used in 
the digitizing of engineering drawing, contour line map 
and land use map and so on, using it to do land use 
Statistics is only one of them, the following is the exam- 
ple. One map sheet of 1:10,000 land use map scanned 
from large size scanner, after the graghic preprocessing 
and line thinning, whose thinning result is shown in 
Fig. 6. From Fig. 7 we can see the vector data that de- 
rived from raster to vector conversion. After the auto- 
matic topology ,the graphic can set up the topoloical re- 
lationship, based on this topological relationship we can 
input the attribute of each polygon and do some land use 
statistics, Finally we can set up the database for statis- 
tical data and do editing, updating, inguirying the 
database and printing the table. 
CONCLUSION 
This system adopts the automatic scan digitizing to 
replace the manual digitizing and realizes the automation 
of the graphic input. So it can greatly increase the effi- 
ciency of digitization. And it can provide a advanced 
means for the graphic input of land use statistics and 
GIS. 
This software system use Paintbrush and Auto- 
CAD to do the raster and vector graphic editing, it can 
greatly increase the efficiency of graphic editing, which 
makes this system more practicable. 
Besides the above mentioned land use statistics, at 
present the customer can use it to do digitizing for engi- 
neering and contour line map. 
REFERENCE 
1. David D. Greenlee, Raster And Vector Pro- 
ceesing For Scanned Linework 
2. Vijay Nagasamy, Engineering Drawing Process- 
ing and Vectorization System, Computer Vi- 
sion, Graphic and Image Processing No. 49, 
379—397, 1990 
3. Andreas Illert and Jun Yang, Extraction Texts 
and Symbols from Unstructured Vector Data