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A. Zlinszky, G. Molnár:
"Georeferencing the first bathymetric maps of Lake Balaton, Hungary";
Acta Geodaetica et Geophysica Hungarica, 44 (2009), 1; 79 - 94.

Lake Balaton is located in the Pannonian Basin, Hungary (46◦50 N, 17◦50 E),
and is characterized by its large area (594 km2) and very shallow water depth (avg.
3.5 meters). The main tributary is the Zala River, which enters the western bay, and
the only outlet is the SiŽo River in the East.
SŽamuel Krieger conducted the first known survey focusing on Lake Balaton in
1776. The original purpose of SŽamuel KriegerŽs work was to illustrate his plans of
draining and canalizing Lake Balaton. This map indicates several proposed canals
and bathymetric contour lines according to a water level drop of 1, 2, or 3.33 Viennese
fathoms (1 Viennese fathom = 1.89 meters). The map also shows settlements, land
use and relief. Krieger measured water input from tributaries, documented the water
level fluctuations of the lake, and summed his results in the "Descriptio", a document
with several tables of data and a written description of Lake Balaton, the SiŽo River,
and the possible benefits of his plan of draining the lake.
Almost 90 years later, the water level was lowered by approximately 1 meter in
1863, cutting off large marsh areas from the water system of the lake. The first
bathymetric map was surveyed in 1895 after the lake was partially drained. The
bathymetric survey was carried out with the purpose of estimating the water volume
held by the lake. Understanding water balance was important for flood control
after the SiŽo Canal and lock was built in 1863. Water depth was measured in 2884
points, along sections near the shore, and scattered points in areas of low relief.
Depth was measured with a sounding line or pole. Horizontal positions were measured
optically from military triangulation points, and elevations were leveled from
a network of benchmarks placed for this survey. Distances were measured in fathoms
but elevations were measured in meters for better accuracy. Reprojection of
the scanned map was possible, but we had to correct minor errors by triangulation.
Surviving benchmarks, depicted buildings and railway bridges were used as control
points. The resulting map was used to create a Digital Elevation Model of the lake
floor for investigating sedimentation processes.

bathymetry; georeferencing; historic maps; Lake Balaton

http://dx.doi.org/10.1556/AGeod.44.2009.1.8

http://www.akademiai.com/content/597p7qw1n40t3422/fulltext.pdf