Jamet -1 
Two examples of semi-automatic capture processes 
in a national mapping agency 
Olivier JAMET, Sylvain AIRAULT, Philippe GUIAVARC'H 
Laboratoire MATIS, Institut Géographique National 
2, avenue Pasteur, F-94 160 Saint-Mandé (France) 
Phone: +33-1-43-98-80-69, Fax: +33-1-43-98-85-81, Email: jamet,airault,phil@matis.ign.fr 
Abstract 
This paper shortly presents two studies on the integration of automatic tools within a 
cartographic data capture process from aerial imagery. The first one concerns road extraction. 
The proposed solution is an interactive environment offering an automatic functionality. The 
second one is the automatic computation of contour lines from the results of an automatic 
correlation algorithm. A first analysis of the operationality of the proposed solutions shows the 
current bottlenecks of automatic techniques, and points out the need for a control of automatic 
procedures by more complete models, in order to achieve a more efficient management of the 
operator interaction. 
Keywords: digital photogrammetiy, aerial images, automation, interactivity 
1. Introduction 
As a national mapping agency, the National Geographic Institute (IGN) is in charge of 
the capture and updating of the French topographic information. In 1985, it was decided 
to build up a topographic database (BDTopo) from a new photogrammetric plotting of 
the whole territory. This new acquisition was to correspond to a complete refection of 
the topographic information, and to a real upgrade of its content and accuracy, 
compared to the former 1:25 000 scale mapping. It is currently running on 24 analytical 
stereo plotters, which will be soon extended with 20 to 24 digital photogrammetric 
workstations. The achievement of the base, that will represent at least 2 millions hours 
stereo plotting, is scheduled within 15 years. 
In this context, IGN is working at introducing semi-automatic tools on its digital stereo 
plotters, in order to shorten the initial capture delay, and to reduce its cost. 
The scope of this paper is to present two examples of automatic tools that have reached 
enough maturity for an operationality evaluation, with a focus on the questions raised 
by their integration in a production line. 
The first one is a semi automatic road plotting method, based on a road tracker 
developed by Sylvain Airault [AIRAULT 93]. After a short presentation of the