CIP A 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
measurements at a profile distance of 1 cm with additional 
breaklines, which gave us about 300'000 points in total. The 
grid calculation with an interpolation software system DTMZ 
developed at the Institute resulted to a regular raster of 1 cm 
grid width. 
Orthoimage generation. The 87 coloured images were 
scanned on an UltraScan 5000 scanner of Vexcel Imaging with 
the resolution of 1270 dpi corresponding to a footprint of 0.4 
mm in the object. This assures that even the smallest relief 
details are clearly visible. For orthoimage generation the system 
SocetSet of LH Systems was used. The resulted mosaic covers 
the whole DTM area and uncompressed has a file size of about 
306 MB. 
Extraction of 3D vector data. In order to get a vector data set 
for the accuracy analysis of Pfyffer’s relief, significant relief 
features like roads, rivers, lakes and settlements were captured 
three-dimensionally in a manual mode on the analytical plotter. 
Texture mapping and visualization. Mapping the orthoimage 
onto the DTM, a variety of visualization products were derived 
(Figure 4): anaglyph images, interactive VRML models and 
flyovers. A virtual flight over the reconstructed relief or an 
online navigation in the model is nowadays as fascinating as in 
the age of Franz Ludwig Pfyffer the relief itself. 
Figure 4. A view of reconstructed model of the Pfyffer’s relief 
(created using the software Skyline) 
The complete digital data set of Pfyffer's relief was archived at 
the Kulturgiiterschutz of Lucerne for the documentation of 
cultural heritage. In case of the damage of the relief or its parts, 
the precise digital data can be used for physical reconstruction 
of the original. 
4. ACCURACY ANALYSIS OF THE RELIEF 
In order to determine the accuracy of Pfyffer’s relief, the 
reconstructed model must be compared with current map 
information. Considering relief distortion in all three directions, 
various methods of spatial geometric transformations have been 
implemented and solutions are proposed in this section. In 
particular, a comparison of the historical terrain model with the 
current data represents a new problem in the historical 
cartography: rather than rectifying and georeferencing a planar 
old map, the 3D model has to be analysed. An important goal of 
accuracy analysis is a good visual presentation of the work; the 
methods and results must be easily understandable for project 
partners - historians with less technical background. As 
programming languages C and Matlab are used. The input data 
and all the results are georeferenced, maintained and visualised 
in ArcView GIS. 
Two data sets are used for the comparison: 
1. Historical data in the local coordinate system: DTM of 
1 cm grid width, orthoimage of 0.5 mm footprint 
(13T20 x 7780 pixel) and structured 3D vector data. 
The data set covers the whole relief area (6.7 x 3.9 m 2 ). 
2. Current data in the Swiss national coordinate system: 
DTM of 25 m grid width, digital map 1:25000 with 2.5 
m footprint and structured 2D vector data VECTOR25. 
The data set covers an area of about 96 x 87 km 2 . 
The accuracy analysis of Pfyffer’s relief is based on a number 
of identical points selected according to principles of historical 
cartography. The procedures described in the following include 
definition and transformation of identical points, transformation 
of image, height and vector data, visualization of the results, 
analysis of lake contours accuracy and the DTM comparison. 
4.1 Definition and transformation of identical points 
Identical points are objects in Pfyffer’s relief, which in reality 
have existed for centuries and which can reliably be found in 
both data sets: churches, crossings, mountain peaks, bridges 
etc. For each point, 3D coordinates x, y, z of historical data in 
the local system and X, Y, Z of current data in the national 
coordinate system are stored. Additionally, identical points are 
assigned to one of three categories according to their estimated 
reliability. In co-operation with historians, overall 221 well 
distributed identical points were defined (Figure 5). 
Figure 5. A chapel on a lake island as a reliable identical point, 
left in Pfyffer’s relief, right in the 1:25'000 map 
To determine the absolute accuracy of Pfyffer’s relief, identical 
points have been transformed using a spatial transformation 
with 9 degrees of freedom - 3 shifts, 3 rotations and 3 scales, 
which proved to be particularly suitable for old relief models 
(see Niederoest, 2002a): 
f’X> 
a: 
V 
(x' 
Y 
= 
■*, 
+ 
m y 
-R(a,j3,r)- 
y 
, m z) 
where x, y, z = coordinates in historical data set 
X, Y, Z = coordinates in current data set 
d x , d y , d z = shifts in three coordinate directions 
m x , m y , m z = scales in three coordinate directions 
a, P, y= rotation angles 
R = rotation matrix