DIGIRAST 
The Powerful Entry Level Interactive Semi-Automated Digitizer 
R. Casini, M. Nardini, M. Scarton 
Galileo Siscam S.p.A. 
Florence, Italy 
ABSTRACT: 
The application of a new approach for data conversion based on interactive semi-automated digitalization 
is described. The realization of a software package based on the same algorithm and based on Personal 
Computer platform is presented. 
KEY WORDS: Data Conversion, Digitalization, Vector from Raster, Line Follower, PC based 
1. INTRODUCTION 
Most of the cost for a complete commissioned job 
in GIS is often due to the conversion of data 
represented on paper sheet. Few of such maps have 
been processed for conversion to digital form and 
both the laboriously hand digitizing and some 
early approaches by expensive software based on 
nowadays obsolete computer equipment failed to 
cut the conversion cost. DIGIRAST starting from 
experiences of both the manual and the complete 
automatic way solves most of the problem using a 
Personal Computer, a standard graphic board, an 
ease to use user interface and an interactive 
approach that allow the operator to check the 
automated digitalization. 
2.DIGITALIZATION OF RASTER DRAWING 
Galileo Siscam has been always very sensitive to 
new needs in photogrammetry and mapping. One of 
those is how to convert old map sheets in a 
simple floppy disk. There are several software 
packages that, using different approaches, are 
able to obtain good results but most of the time 
they run under expensive or not standard 
workstations and they approach the problem in a 
complete automated way. 
Unfortunately by a complete automated method the 
map sheet, with there coded information and all 
kind of different symbols, are very difficult to 
interpret and the user often dislikes to correct 
the mistakes off line and spending anyway a long 
time. The operator would prefer to control this 
job in progress in an interactive way. 
Furthermore due to the nowadays high performance 
Personal Computers and due to their cost much 
lower than any workstations the need is also for 
a package able to run on this platform with the 
most common operating system as MS/DOS . 
So DIGIRAST was born. DIGIRAST is a software 
package written in C language addressed to 
transform any raster format drawing in vector 
format drawing but with a particular 
specialization in cartographic drawing as contour 
lines maps, cadastral and tax maps at low and 
high scale. 
It has been taken particular care to the graphic 
by implementation of routines and data structures 
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particularly suited for a real time management of 
the raster and vector image by means of  panning 
and zooming at high speed. 
One of the biggest problem to be solved is how to 
adapt a digitalization method to the different 
cartographic information contained in every 
different maps. For example, the information 
contained in a contour line is quite simple: 
following the line and getting x-y coordinates, 
associating the relevant z of the contour to each 
point of the line. The situation is different for 
a tax or cadastral map: the line to be followed 
is most of the time a closed property border line 
it is better to start from the inside of the 
property, getting to the perimeter and then 
following the line. Besides that, why do not use 
the display of the computer as a standard 
digitizer with advanced functions as zoom and 
automated coding? 
The Digitalization has been provided with three 
different methods to answer to these and other 
further needs: 
- Manual 
Semi-automated by DIRECTIONS 
Line Following 
2.1 The digitalization in plate coordinates 
The cartographic drawings have a big difference 
respect on the mechanical drawing: the coding. In 
fact a cartographic drawing is not just a set of 
lines but it consists of information as type of 
line, color, thickness, code of elements, 
elevation. So to avoid the mistakes and the lack 
of information that a traditional automated 
digitalization software produces, it has been 
preferred to maintain a level of freedom to the 
operator. Instead of running an automated 
procedure that produce a final vector file with 
many errors to be corrected anyway off-line by 
the operator, by means of DIGIRAST the user is 
able to follow the job and then to decide when to 
input other information or to correct some errors 
in real time. The final goal is to decrease 
drastically the revision time of the final vector 
file that anyway has to be performed by a CAD 
software after the digitalization. 
But sometimes it is not possible to use just one 
of the above mentioned methods. The experience