International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
sketches (Fig. 10a). Due to the lines of sight to the surrounded,
precisely labelled or numbered summits it was previously
assumed that Pfyffer created these drawings in connection with
his surveying. However, a recent analysis with the help of
landscape models has shown that the sketches were created and
also used much later for the formation of the relief surface.
Their distorted geometry excludes any systematic, perspective
or panorama-like landscape projection, whereas the quality and
excessive details of the morphology are amazing (Fig. 10). The
computer-generated views confirm Pfyffer's concentration on
the forms of selected mountains and his disregarding of
geometric aspects in the surrounding area. The crucial point of
the analysis was to find the places where the sketches had been
drawn, which was not an easy task due to the distortions,
unusual fields of view and missing or confusing station
descriptions.
4. PFYFFER'S PROCEEDURES AND RESULTS IN
EUROPEAN COMPARISON
The first product of modern geodesy and systematic land
survey was the Carte géometrique de la France (1739-1793) at
a scale of 1:86'400. The state- and military supported mapping
of France under the direction of four generations of the Cassini
family was based on one superordinate and two subordinate,
computationally evaluated triangulation networks. With the
exception of this work, nearly all other 18th century maps were
created applying similar procedures and instruments to those of
Pfyffer. The following outstanding cartographic products based
on graphical triangulation using a plane table and simple
instruments to measure angles can be mentioned:
e The huge work of military officers of the Habsburg
monarchy at a scale of 1:28'800, created within the first, so
called Joseph's survey (Josephinische Landesaufnahme,
1764-1787) and covering several countries of today's
central and eastern Europe.
e The Atlas Tyrolensis at a scale of 1:103'000, created by P.
Anich and B. Hueber between 1760 and 1769. The atlas
depicts a large area of northern Tyrol in Austria.
e Schmettaus map of Preussen (Schmettausche
Kabinettskarte, 1767-1787) at a scale of mostly 1:50'000,
covering a big part of present Germany.
e. Schmit's map of south Germany (Schmittsche Karte,
1793-1797) at a scale of 1:57'600.
e The Atlas Suisse (1786-1802) at a scale of about 1:110'000
by J. R. Meyer, J. H. Weiss und J. E. Müller. The atlas
displays the entire area of Switzerland.
In order to be able to interpret the geometric quality of Pfyffer's
topographic work (Table 1), the results of numerical evaluation
of other maps of that period must be taken into consideration.
Unfortunately, the research on accuracy analysis of 18th
century maps is very rare and in addition, the measures used to
express map accuracy are usually very diverse. The numeric
results of several investigations are shown in the following:
e According to (Finsterwalder, 1988), the mean position
error of 38 identical points of the distortion grid of the
mentioned Schmittsche Karte (1793-1797) of south
Germany is +2.5 km. The middle distance error of this
map by the average distance of 15 km amounts to +1 km.
e (Brunner, 2002) analyzed the accuracy of the first
topographic land survey of Sachsen in Germany (so called
Meilenblátter. 1780-1825). This map at a scale of 1:12'000
is based on theodolite measurements and a numerically
evaluated one-step triangulation. Within the accuracy
analysis, the map sheet size was compared with its to-be
value of one local mile (6796.56 m). The map is very
precise: the 15 sclected map sheets created in 1785, 1797
and 1810 deviate from this value in average of 3 m, 68 m
and 14 m respectively.
e As a representative of Swiss 18th century maps, the
already mentioned Atlas Suisse (1786-1802) - considered
to be the best map of the country until the first official land
survey - was analyzed within the presented project. For the
accuracy analysis the sheet Nr. 7 covering the area of
Central Switzerland was selected. The evaluation using
115 identical points and applying the same procedures as
those for the maps of Pfyffer (Section 2) resulted in the
sigma a posteriori of 335 m in the X- and 247 m in the Y-
direction respectively.
The way of creation of the above listed European maps provide
evidence that at the time of Pfyffer's surveying and relief
construction (1750-1786) his procedures and instruments were
up to scientific standards of that period. His results hold well
with the accuracy of contemporary maps and in particular, his
substantial contribution lies in performing pioneering area-wide
height measurements and detailed 3D modelling. Considering
the conditions under which the relief was constructed - an
unfavourable age for landscape exploration and surveying in
Switzerland and a large mountainous area modelled at a large
scale - Franz Ludwig Pfyffer's achievement is admirable even
from today's point of view.
5. CONCLUSIONS
Finished in 1786, Pfyffer's relief attracted numerous visitors
from all over Europe to Lucerne. Its unusual bird's eye
perspective of an inaccessible mountain barrier was an absolute
novelty, a virtual flight in the age of enlightenment. However,
with the appearance of new, more precise maps at the turn of
the century the opinions on the topographic quality of the relief
started to change; the relief was reduced to a kind of handicraft
and had almost been forgotten. Due to its complexity and a lack
of primary documentation the relief was never investigated
until the procedures of photogrammetry and image analysis
allowed for drawing conclusions from the geometric evaluation.
The results of the presented interdisciplinary research give the
painstaking work of Pfyffer its original value back again. The
relief must be considered an excellent topographic achievement
of that time and a milestone on the way to modern cartography.
REFERENCES
Brunner, H., 2002: Wie Sachsen vermessen wurde. Die
Meilenblätter und die kursächsische Landesvermessung von
1780 bis 1825. Dresden, pp. 91-92.
Finsterwalder, R., 1988: Massstab und Genauigkeit alter Karten
- gezeigt an einigen Kartierungen Bayerns. In: Cartographia
Bavariae: Bayern im Bild der Karte, München, pp. 193-211.
Fischer, G., Schnegg, P.-A., 1994: Updating the geomagnetic
survey of Switzerland, in Matériaux pour la Géologie de la
Suisse. Géophysique No 27. Neuchátel, Fig. 2.
Niederüst, J., 2003: A bird's eye view on Switzerland in the
18" century: 3D recording and analysis of a historical relief
model. IAPRS, Volume XXXIV-5/C15, pp. 589-594.
Pfyffer, F. L., 1761: 10 letters of Pfyffer to Micheli du Crest,
from April 28 to September 15. Landecy, Arch. Micheli,
Papiers JBMC no 720bis.
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