International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
[In a previous publication (Niederóst, 2003) the methods for the 
digital recording of Pfyffers Relief and the quantitative 
evaluation of the virtual relief and related old maps were 
presented (they are shortly summarized in Section 2). The 
analysis yields a number of statistic and visual products, which 
have a great potential for the research in the history of 
cartography. Now the most important question is to be 
answered: Which conclusions can be drawn from the results of 
the accuracy analysis? This paper aims at the reconstruction of 
Pfyffers surveying procedures (Section 3) as well as at the 
interpretation of the estimated relief accuracy in the context of 
European cartography in the 18th century (Section 4). The 
research is based on several sources: a few autographic letters 
(Pfyffer, 1761) and maps of Pfyffer, archive publications as a 
testimony of the surveying and cartographic standards of that 
time and of course, the results of the performed quantitative 
analyses. 
2. DATA PROCESSING 
For the generation of a 3D computer model of Pfyffer's Relief, 
the procedures of image-based object reconstruction were 
applied. The photogrammetric stereo processing resulted in a 
digital surface model of 1 cm raster width, an orthoimage and a 
structured vector data set of significant relief features. The 
precise digital data set of Pfyffers Relief including 
visualization products (Fig. 2) was archived at the 
Kulturgüterschutz of Lucerne for the documentation of cultural 
heritage. 
    
dens 
reconstructed 
Fig. 2: A view of the photogrammetricall 
texture-mapped Pfyffer Relief 
tt 
The accuracy analysis of Pfyffer's Relief is based on a number 
of identical points in the historical and modern data set. 
Applying a 9-parameter spatial transformation, the accuracy of 
the relief as well as its metric parameters such as scales and 
rotation angles were determined. The calculated distortion grid 
(Fig. 3) allows for a visual presentation of the numeric results 
of the analysis. Furthemore a new procedure for georeferencing 
of the historical height, image and vector data was developed. 
The overlay of the georeferenced data set with the current map 
information (Fig. 1b) represented a basis for the numerical 
accuracy analysis of polygonal relief features such as lake 
forms. Finally, the surface of Pfyffer's model was compared 
with the national terrain model DHM25 of swisstopo. 
In order to understand the spatial and temporal coherences of 
the relief creation, the following relief-related old maps were 
also included in the analysis (see also Table 1): 
   
   
  
: rA Ea i rug dam 
Fig. 3: The distortion grid of Pfyffers Relief showing the 
deformation of 2-km coordinate lines on the background of the 
current national DTM (DHM25, copyright swisstopo). 
e The coloured small-scaled drawing of Central Switzerland 
by Pfyffer's own hand (Fig. 4), 
e The fragment of a large-scaled manuscript map of Pfyffer 
from the region of Rengg valley, which was - re-used as 
wasted paper - surprisingly found inside the relief during 
its restoration (Fig. 5), 
e The engraved Carte en Perspective du Nord au Midi, 
created by Jakob Joseph Clausner (1744-1795) on the 
basis of Pfyffer's measurements in 1786 (Fig.6). 
  
      
    
Bier d | ———3À2km | 
Fig. 4: A part of the georeferenced manuscript map of Central 
Switzerland of F. L. Pfyffer overlaid with current lake contours. 
: A part of the large-scaled manuscript map of F. L. 
Pfyffer overlaid with residuals on identical points (red lines). 
  
  
    
Inter. 
  
  
Tabl 
obse 
map 
3. 
FE. 
perf 
a co 
a se 
gain 
serv 
Surv 
inst 
Bac 
hom 
forn 
exis 
chal 
incl 
ove 
3.1 
On 
Swi