1. INTRODUCTION 
With the extended spreading of geographic 
information systems (GIS) high demands are 
made on photogrammetry and mapping. As the 
underlying data is of utmost importance for 
geographic information systems, the need for a 
fast and cost-effective data acquisition changes 
the pre-requirements and working procedures in 
photogrammetry and mapping tremendously. 
The new photogrammetric and mapping 
methologies are characterized by: 
- kinematic methods 
- sensor fusion 
- increased automatization 
- real-time applications 
From all the above mentioned characteristics the 
real-time aspect is by far the most demanding, as 
it implicitly contains all the other mentioned 
features. In real-time photogrammetry and 
mapping, data acquisition is usually kinematic. 
Further, the real-time aspect can often only be 
solved if a full automatization of all data 
processing steps can be guaranteed. And this 
automatization can only be achieved if as much 
information as possible can be gathered from a 
multi-sensor system. 
In principle, two major problems have to be 
solved in real time mapping applications. On 
one hand the parameters of exterior orientation 
have to be determined for the full description of 
the observation geometry (see fig. 1). And, on 
the other hand, as much information as possible 
about the object space is required for the real- 
time, automatic reconstruction and classification 
of relevant objects. The automatic reconstruction 
and classfication of objects from image or other 
data sources is a highly complex problem and 
for the time beeing it can only be solved in real- 
time for some specific applications. This 
automatic interpretation step is a highly complex 
research topic on its own and it will not be 
treated in the remainder of this paper. Rather, 
the paper will concentrate on the real time 
determination of exterior orientation parameters 
with the aid of the NAVSTAR/Global 
  
  
  
  
[Figure 1 Exterior Orientation Parameters 
  
Positioning System (GPS). Again, the problem 
of determining the exterior orientation of a 
sensor platform can be divided in two seperate 
tasks. The exterior orientation of airborne sensor 
systems consists of a positioning part for the 
determination of the projection center 
coordinates (X,, Y, Z,) and an attitude part 
where we have to solve for the attitude (c, d, K) 
of the sensor system with respect to a known 
coordinate system. 
2. REAL-TIME DETERMINATION OF 
PROJECTION CENTER COORDINATES 
The precise determination of the projection 
center coordinates of airborne sensors has been 
significantly simplified by the recent 
development of the NAVSTAR/Global 
Positioning System (GPS). Although, GPS real- 
time, high precision positioning has become 
routinely available for airborne 
photogrammetric and mapping applications, 
extreme care has to be taken especially for large 
scale mapping. Depending on the map scale the 
positioning accuracy requirements for mapping 
applications can be fairly stringent (see table 1). 
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