Acta Geod. Geoph. Hung., Vol. 44(1), pp. 79–94 (2009)
DOI: 10.1556/AGeod.44.2009.1.8
GEOREFERENCING THE FIRST BATHYMETRIC
MAPS OF LAKE BALATON, HUNGARY
A Zlinszky1 and G Molnár2,3
1 Balaton
Limnological Research Institute of the Hungarian Academy of Sciences,
POB 35, H-8237 Tihany, Hungary, e-mail: azlinszky@tres.blki.hu
2 Institute
for Photogrammetry and Remote Sensing, Vienna University of Technology,
Gußhausstraße 27–29, A-1040 Wien, Austria
3 Space
Research Group, Department of Geopyhsics, Institute of Earth Sciences, Eötvös
Loránd University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary,
e-mail: gmo@ipf.tuwien.ac.at
Open Access of this paper is sponsored by the Hungarian
Scientific Research Fund under the grant No. T47104 OTKA
(for online version of this paper see www.akkrt.hu/journals/ageod)
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 Sió River in the East.
Sámuel Krieger conducted the first known survey focusing on Lake Balaton in
1776. The original purpose of Sámuel Krieger’s 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 Sió 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 Sió 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.
Keywords: bathymetry; georeferencing; historic maps; Lake Balaton
c
1217-8977/$ 20.00 2009
Akadémiai Kiadó, Budapest
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A ZLINSZKY and G MOLNÁR
Introduction
Historic maps were always an important source for detecting changes in the
natural and culturally influenced environment. Geoinformation technologies allow
for accurate georeferencing and quick numeric measurement of possible changes in
the landscape depicted. The first thematic maps of a given area always represent
an important starting point for environmental research, so their georeferencing and
processing is crucial for understanding the spatial and time scale of changes on the
study area.
This paper presents a case study on the history, georeferencing and possible use
of the first bathymetric maps of Lake Balaton: The Balaton map of Sámuel Krieger
(1776), and the map of the first bathymetric survey of the lake (1895).
The main objective of digitizing Krieger’s map was to gain knowledge on the
area of wetlands adjoining Lake Balaton, and on habitats and land-use practices
around the lake. The first bathymetric survey represents the starting point of the
long process of measuring sediment accumulation in the Balaton Basin.
Study area
Lake Balaton is the largest lake in Central Europe, with an area of 594 km2 . The
lake lies in a shallow depression of probable neotectonic origin (Cserny and NagyBodor 2000) in the SE foreland of the Transdanubian Mountains in the Pannonian
Basin. The lake can be divided into four embayments: the Keszthely Basin, which
is the smallest and shallowest and receives the Zala River, the main tributary of the
lake; the Szigliget Basin, which was connected to extensive wetlands adjoining the
northern and southern shore; the elongated Szemes Basin which stretches between
uplands in the North and rolling hills in the South; and the largest of the four,
the Siófok basin, which has small bights with reed beds on the North, elevated
cliffs on the Eastern shore and beaches on the Southern shore (Fig. 1). The main
watercourse entering the lake is the Zala River, which runs from the forelands of
the Alps in Western Hungary through hills and a constructed wetland into the SW
of the lake, and generally supplies enough water to balance evaporation from the
surface of the lake. Some small streams enter the Szigliget Basin from the Northern
shore, but the rest of the lake is fed by the steady flow of water along the axis of the
lake and by some ephemeral torrents. The water level of Balaton is regulated by
occasional draining through a sluice system and lock gate located at Siófok. This
was built on the Sió River in 1863, which sometimes acted as a natural outlet of
the lake before the construction but probably ran dry between periods of extremely
high water level. The Sió River has a very slight slope, and its transport capacity
is low despite several canalization efforts. The building of the sluice and canal had
a drastic effect on the lake: it resulted in the lowering of the water level by more
than a meter, separating large wetland areas that were previously connected to
the water system during floods and changing the water balance of the lake due to
reduced evaporation.
Presence of human settlements can be documented around the lake since
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81
Fig. 1. Lake Balaton and its surroundings. Z.R.: Zala River, K.: Keszthely, T.B.: Tapolca Basin,
Sz.: Szigliget, Fo.: Fonyód, B.: Boglár, BF.:Balatonfüred, Ti.: Tihany, S.: Siófok, F.: Fűzfő, S.R.:
Sió River, K.B.: Keszthely Basin, Szig. B.: Szigliget Basin, Sz.B.: Szemes Basin, S.B.: Siófok
Basin. Numbered rectangles indicate approximate location of Figs 3, 4, 5 and 8
Neolithic times (Bendefy and V Nagy 1969). Human influence on the water level
of the lake is assumed by some to have started by the Romans, and although this
cannot be proved (Virág 1998), it shows that the lake and its surroundings are in a
semi-natural state since early times. In medieval times the lake was used for fishing
and as a transportation route when it froze over, and villages were built on elevated
land in a slight distance from the shore. The coastal areas were used for grazing and
valleys were used as ploughed fields while the slopes of the uplands on the northern
shore gave excellent vineyards since the Bronze Age (Virág 1998). The lake was
an important strategic border during the occupation of Hungary by the Ottoman
Empire in the 16th and 17th century and the remains of fortresses can still be found
on many hilltops around the area.
The use of the lake for recreational purposes started in the late 19th century, and
resorts and holiday villas were built on the previously uninhabited shore. The lake
was a popular holiday destination for Austrians and Germans as well as Hungarians
during the second half of the 20th century, and during the 1970’s and 1980’s, nearly
all the southern and large stretches of the northern shore were built in by hotels,
beaches and holiday homes. The widespread use of agricultural fertilizers and the
pollution caused by sewage discharged into the watershed of the lake led to intensive
eutrophication of Lake Balaton in this period, and large-scale pollution control
measures were initiated to solve this problem. The building of sewage works in the
towns of the watershed and the rise of the price of fertilizer reduced the nutrient load
of the lake, and nowadays the water quality is back to normal. The conservation
of the remaining natural wetlands around the shore remains a major concern, as
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A ZLINSZKY and G MOLNÁR
Fig. 2. The Balaton map of Sámuel Krieger (1776)
the reed stands are negatively affected by the stabilization of the water level (van
der Putten 1997). The sediment dynamics of the lake are also an important issue
of research, since the shallow Keszthely Basin receives large amounts of sediment
from the Zala River. The examination of the following maps provides information
badly needed for tackling these problems.
Sámuel Krieger’s map of Lake Balaton (1776) (Fig. 2)
History
The canalization and eventual full drawing off of the lake was first planned under
Queen Maria Theresia in the 18th century (Bendefy 1973). The main cause for this
was probably the fact that the army of the Habsburg Empire had switched to
central provisioning under Maria Theresia, and this meant an expanding demand
for agricultural products and also a strong need for safe water transport. The
center of the agricultural market was the town of Graz, and a large-scale navigable
canal network was planned to enable the shipping of grain from the Hungarian
Plain to Graz, along the rivers Danube, Sió, Zala and Mura through Lake Balaton.
The wetlands and open water of the lake were considered unhealthy areas with no
possible use for agriculture, and landowners around the lake were also interested in
enlarging field and pasture areas.
A royal commission was established in order to investigate the possibilities and
costs of draining Lake Balaton. Sámuel Krieger was a young surveyor who graduated at the Military Academy of Gumpendorf in 1768 and worked as an official
engineer for Zala County and later the town of Sopron (Bendefy 1972). We have no
written record of Krieger’s measurement methods, but the high quality and accuracy of the map suggests he used state-of-the-art methods of his time to complete
it: triangulation, leveling and astronomical geodesy. He also measured the depth
of the lake at several points. The surveyor summarized his measurements and recommendations to the royal committee in a detailed description in Latin, in five
written pages and several adjoined tables. This was republished by Cholnoky in
1918 in original language to save it from possible destruction (Krieger 1776a). As
this description has not been translated into English, and it gives unique first-hand
information on the features of the map and the condition of the lake in that time,
we find it necessary to cite a part of our translation of it in spite of its lengthiness
and occasional contradictions.
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83
“The lake originates from the river Zala, which meets numerous becks, torrents
and rivers that are summarized in table VI. The lake is completely covered with
swamps of reeds and sedges from its origin to the island of Iszép. The rest of the
lake’s waters are clear except on the northern shore where they are polluted by
some reeds. Its bottom is flat around its circumference, and rocky or muddy, or
if we note all differences, the northern side can be considered rocky, the southern
sandy, the eastern covered with pebbles and the western with swamps. Its depth in
its normal state is one fathom around the territory of Vörs and in the marshes of
Hévı́z, and this is the shallowest area, and it deepens uniformly towards the ferry
of Tihany, where it measures four and a half fathoms. This is the deepest point, so
the waters can run here from the vicinity. There are some other areas where the
water is somewhat deeper or shallower, but these are not worth considering because
of their small size.
Three dotted lines are drawn on the map: one painted with grey-green which
shows the depth of one fathom. The next, coloured green outlines the depth of
two fathoms, and the third, blue outline contains the depth of three fathoms and
two feet.
(The water level) rises from the month of October until April, this has an average
of two feet; and decreases from June to September by two feet again in two months.
The total difference is three feet, or three and a half in very dry years, which means
the maximum depths vary, as table VII shows. I think it decreases in dry periods to
such extent that it is no wonder that the mouth of the Sió (which is three fathoms
and five and a half feet higher than the deepest point of the lake) dries to the very
bottom, since the closer the bottom of the outlet of Sió would be, the more the
water level would have to decrease to cause such an event.”
Features
Two original remainders of Sámuel Krieger’s map exist to the present day, both
are hand drawn, probably by the Author himself. The manuscript which is now in
the Hungarian National Archives (Krieger 1776 (1766)) has a large and decorated
title field and a long official title (with an incorrect date, (Virág 1998)) and is probably the map that was presented to the royal committee. The second manuscript
is in the Archives of County Zala (Krieger 1776b), this is more simple with no title
area or other decorations, and was probably ordered by the County Zala. This
latter map was used in our investigations. Cholnoky describes two more original
specimens of the map (Cholnoky 1918), but these were destroyed during World
War II.
The map shows the administrative territories of settlements around the lake,
including the areas to be gained by the planned lowering of the water level. It also
depicts the canal system Krieger planned: one canal from the mouth of the Zala
River along the northern shore to the deepest point of the lake (labeled canalis fluvii
Szala navigabilis: navigable canal of the Zala River), the outlet canal eventually
planned to run from the straits of Tihany to the town of Fok (the present-day
city of Siófok) and along the Sió River, and a canal along the southern shore of
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Fig. 3. Extract of the Krieger map showing the area of the lake divided according to the extension
of the borders of the village territories on the shore, a proposed canal, and the road from Boglár
to Fonyód along the top of the sandbar
the Szigliget Basin to collect the waters of the swamp (labeled canalis secundarius
pro aqua superflua: second canal for overflowing waters), and the area of the lake
which would remain according to the maximum water level descent of three and
a half fathoms (labeled Residuum ex Lacu Balathon post demissionem ad pedes
20 juxta projectum 3ium: remaining area of Lake Balaton after descent of 20 feet
according to plan 3) (Fig. 3). Krieger proposed three separate plans based on
the same canal system: decreasing of the water level by 1 fathom, 2 fathoms or
three and one-third fathoms. He calculated the areas the settlements would gain
and also the profits to be earned if the resulting areas would be used as meadows,
according to plan 1, 2, and 3, summarizing these numbers in the tables of Descriptio
(Fig. 3). Krieger probably traveled all around the lake, as the roads and roadhouses
are very well mapped. The agricultural use of the territories of each settlement are
also meticulously mapped, with separate symbols depicting areas of ploughed fields,
meadows, forests, sandy coastal areas, and reed-covered wetlands. The symbols he
used are very much the same as the cartographic pictograms we use today (Fig. 4).
The colors are quite uniform and the lines are of remarkably even thickness which is
amazing for a hand-drawn map of 180× 40 cm. Krieger also mapped elevations, and
used fine hachures to symbolize slopes of valleys and mountains. Built-up areas of
settlements and some distinctive buildings are shown as approximate ground plans
in red with the lines of streets running between, but water-driven mills are carefully
mapped with little circles on the streams (Fig. 5). Krieger measured the height of
several mill dams since this was important for levelings of watercourses and listed
them in Table IX of Descriptio.
Krieger probably measured bathymetry in some places along the shore, since
he had to calculate the area to be won by lowering the water level. The depth
contours of 1 and 2 fathoms are very similar to the contours that can be measured
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BATHYMETRIC MAPS OF LAKE BALATON
85
Fig. 4. Extract of the Tihany Peninsula on the Krieger map, showing cartographic symbols and
land use
today according to the latest bathymetric survey (Sass 1979), but the contour of
3.33 fathoms is quite different. The bottom of the lake has a slight dip towards the
south, and the deepest area of the lake is very near the southern shore, not in the
central part as mapped by Krieger. As the lake floor has hardly any relief, Krieger
probably failed to notice this slight slope. He probably measured along the depicted
line of the 3.33 fathom contour and assumed the deepest part to lie between them,
which corresponds to the bathymetry he illustrated on the map.
Georeferencing
The map depicts most of the present-day settlements around the lake, and the
roads and the layout of buildings in the village centers can be assumed to have
remained unchanged. The crossings of the main streets of the villages on the map
were used as ground control points. As the axis of main roads around the lake has
also remained relatively unchanged, the location of bridges over some watercourses
could also be identified and used as ground control points, as well as some mills
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Fig. 5. Cutout of the Krieger map showing watermills, wetlands and the proposed outlet canal in
the vicinity of the town of Siófok and the outlet of the Sió River
and a church tower. ER Mapper 7.01 software was used for georeferencing, and 36
control points were located on the Krieger map and the 1:1000 national topographic
map of the region (surveyed between 1957–1980) we used as a reference. Linear
transformation was applied, and the RMS error of the points is under 70 pixels, or
350 meters. This may not seem very accurate, but mapping errors that may have
been caused by the simple methods Krieger used are estimated to be in the same
order of magnitude.
We had to face some problems due to the map’s large size (180 × 40 cm), since
we wanted to find a method for accurately georeferencing it while keeping the size
of the file small enough for computer visualization. The original map was scanned
on a wide format scanner (VIDAR Atlas 40) at the Department of Cartography
and Geoinformatics of Eötvös Loránd University in Budapest with a resolution of
400 dpi and a color depth of 24 bpp, but as the resulting file was over 2 GB it
could not be opened with most laptop or desktop PC-s. The Eastern and Western
parts of the map were also scanned separately, but even these separate files were too
large to handle. The files were LZW compressed and resampled to 250 and 100 dpi
(SCP EasyScan 7.1). Georeferencing was carried out on the 250 dpi copy, and the
resulting map file was cut up into a mosaic of tiles. As a final step, Global Mapper
9 software and a powerful desktop computer was used to georeference the scanned
and LZW compressed original file of 400 dpi, using the previously georeferenced
and resampled image of 250 dpi as a reference. The georeferenced 400 dpi file was
also cut into a mosaic of 6 × 3 separate GeoTiff files to enable handling of the tiles
with conventional software. As a result of this procedure, the Krieger map can now
be evaluated and distributed in full detail for further studies.
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BATHYMETRIC MAPS OF LAKE BALATON
87
Results
As the main objective of georeferencing the Krieger map was to gain knowledge
about the natural state of wetland areas around the lake before the lowering of
the water level, these were thoroughly investigated on the map. The large reeddominated areas of the present-day Kis-Balaton and Tapolca Basin are shown to be
in direct contact with the lake. Today, Kis-Balaton is a reconstructed wetland area
to the West of the Keszthely Basin, and the Tapolca Basin also has large reedswamps
and wet meadows fed by the northern tributaries of the Szigliget Basin, but no open
water. The water depth of these areas is shown to be under 1 fathom, and in some
places roads are mapped that lead across them. As Krieger documented the annual
water level fluctuation of the lake to be around three or four feet in Descriptio, it
is well possible that these reed areas were under shallow water in the winter and
dry during summer. On the southern shore of the lake, the wetlands SW of Boglár
are shown to be separated from the lake by a thin sandbar (Fig. 3). The road from
the village of Boglár to Fonyód (now major towns on the southern shore of the
lake) runs along the top of this bar, exactly the way it runs today. The southern
edge of the Fonyód wetland is not shown on the map, probably because Krieger
did not travel around it. Several smaller reedswamps are mapped on the southern
shore (near the villages of Lelle, Szemes, Szárszó, and Köröshegy) but these are all
separated from the lake by the sandy shoal. The reedlands on the Szántód tombolo
triangle are in direct connection with the lake on the Western side and separated by
a sandbar on the East. The outlet of the river Sió is shown clearly to the West of
the town of Siófok, and has two water-mills on either side of a small island. Under
the mills, the valley opens up into a wetland area with the river branching between
several islands (Fig. 5).
However, absolutely no reed stands were mapped by Krieger on the Northern
shore of the lake from the border between the Szigliget and Szemes Basin all the
way to Fűzfő, except on the NE side of the Tihany Peninsula. The northern shore
of the lake is steep and the hills run directly down to the water, sheltering many
small bays and coves. These bays are covered by large reed stands today, and the
presence of the reeds on the northern shore is documented since the 1900-s (Borbás
1900). Krieger probably visited these areas, since the road, the settlements, the
fields and the shoreline were carefully mapped all along the northern side of the
lake. We have to accept that the reed areas in the bays of the northern shore were
formed later than the wetlands of the Tapolca Basin and the small spot of reeds
near Tihany.
Agricultural areas are abundant all around the lake, and can be found in many
places where forests stand today. The most striking example is the Tihany Peninsula, which now has large forests and protected nature areas, and was nearly completely occupied by vineyards, pastures and ploughed fields in the 18th century
(Fig. 4).
The oldest known map of a complete survey of Lake Balaton, the Krieger
map thus provides us with valuable information on the ecological history of the
Balaton region.
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A ZLINSZKY and G MOLNÁR
The first bathymetric survey and map of Lake Balaton (1895) (Fig. 6)
History
The canal system Krieger planned was not built because of financial difficulties,
since the landowners around the lake were not willing to pay the price of the drainage
works. The plans for lowering the water level of the lake were subject of discussion
for a long time, and some of the mill dams on the Sió were demolished in order
to lower the water level. The Southern Railway line between Budapest and the
Adriatic Sea was built along the southern shore of the lake. There were no regular
measurements of the water level in that time, so the tracks were laid along the top
of the sandbar separating the wetlands from the lake. This was possible because of
a period of drought in Hungary, and after the water level of the lake rose back to
normal, the waves and especially the ice caused serious damage to the railway. The
Southern Railway Company offered to pay the price for building the canal and lock
system previously planned if the water level of the lake would be lowered by one
meter. This was accepted by the national authority and the landowners around the
Sió, and the canal was eventually opened in 1863.
This was expected to solve the problem of flooding around the lake, but as the
1870-s and 1880-s were years of exceptionally wet weather, it soon turned out that
the canal was not large enough to maintain the lowered water level. As one of the
important steps of scientific investigations, the surveying of a bathymetric map of
the lake was initiated in order to gain better understanding of the water volume and
balance of the lake. The Balaton Committee of the Hungarian Geographic Society
wrote a report to the Minister of Agriculture to draw attention to the importance
of a bathymetric survey for biological and geological research. Work was started
in 1891 by locating water gauges and elevation benchmarks at several places on
the shore. The years 1892 and 1893 were dedicated to the leveling of the elevation
benchmarks, the water depth of the lake was measured along sections perpendicular
to the shore in 1894, and the points in the central area of the lake were surveyed in
1895. The processing, mapping and publishing of the measurements was completed
in 1897 (Péch and Erdős 1898). Elevations were measured from the water level of
the Adriatic Sea. On the southern shore of the lake, elevation benchmarks of the
military survey were already located, but no benchmarks were built on the northern
shore of the lake. These new fixpoints were leveled and the measurements were also
connected to points of the military triangulation network. As the main objective
of the depth measurements was to complete a map of bathymetric contour lines of
the lake, measurement points were placed unevenly, in places thought to represent
the relief of the lake floor. The relief is quite distinctive for this lake: the lake
bottom is nearly completely flat on most of its area (with a slight dip to the South),
the North shore is relatively steep, the southern is flat, with a submerged sandbar
of about 1 km width all along the southern shore and a steep wall between the
sandbar and the deepest part of the lake, an area parallel to the lake’s axis and
about 1 km from the southern shore. As the main changes of relief are relatively
near to the shore, this zone was measured in transects running from the shore to
the deep water. The angle of the section was set to be perpendicular to the shore
Acta Geod. Geoph. Hung. 44, 2009
Fig. 6. The map of the first bathymetric survey of Lake Balaton (1895)
BATHYMETRIC MAPS OF LAKE BALATON
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A ZLINSZKY and G MOLNÁR
by triangulation with a sextant, or by measuring from the axis of the railway line.
A theodolite was used to fix the direction of each section perpendicular from the
shore, and distance along the sections was measured optically. The maximum range
for measuring distance optically was 1500 meters, so in areas further from the shore
water depth was measured at points determined by triangulation. 2884 points were
measured, covering the whole are of the lake, which adds up to about 5 points/km2 .
Features
The geodetic basis of the map was the stereographic projection of the Second
Military Survey (Geodetic Datum: Buda 1863) where distances were measured in
fathoms. The survey itself was completed in metric units and the map has a grid in
fathoms and a scale bar in kilometers (Fig. 7). As the survey area covers 11 sheets
of the military survey and each of these has its own coordinate system, a separate
coordinate system had to be compiled for the map. This was based on fixpoints of
the cadastral survey, and differences were equalized. The map has a scale of 1:150
000, and the grid interval is 4000 Viennese fathoms. As not all points could be
plotted due to lack of space, only points with integer depth values were selected and
mapped (Fig. 8), 1300 points altogether. The interval of the bathymetric contour
lines is 1 meter. The map shows very few objects on the shore, but the tributaries
of the lake are included. Landmarks used as triangulation points for navigation
are shown in black (hill tops, church towers, other buildings) including the railway
line with stations. The hydrographic benchmarks used for leveling are printed in
red, and a detailed list was published on their exact elevations and location (Péch
and Erdős 1898). Some of these benchmarks (mainly those built into the walls of
churches) still survive to the present day (Fig. 9).
Georeferencing
The original copy of this map could not be found, but the published version
(which is half the size of the original) could be obtained in a scanned format from
the library of the Geological Institute of Hungary (Péch and Erdős 1898). The Old
Hungarian Stereographic projection of this map is recognized by ER Mapper 7.01,
but Viennese fathoms had to be converted to meters for known point registration.
We reprojected the map into the Hungarian Uniform National Projection (EOV)
for processing, but the results were unsatisfying due to probable mapping errors.
As a relatively large number of landmarks suitable for ground control points could
be identified (benchmarks, triangulation points, railway bridges etc.) triangulation
could be used for local-scale correction of georeferencing. The reprojected map
was georeferenced by triangulation based on 63 ground control points, which were
located on the same 1:10 000 Hungarian topographic map used for the Krieger map.
The average RMS error of these control points was 10 pixels with the largest being
17 pixels. (Pixel size was 12.5 meters.)
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BATHYMETRIC MAPS OF LAKE BALATON
91
Fig. 7. Title field, scale bar and grid of the map of the first bathymetric survey. Indicated
length of scale bar: 10 km. Translation of inscriptions: Öl: Viennese fathom; Mérték: Scale; A
BALATON TÉRKÉPE : Map of Lake Balaton; A VÍZMÉLYSÉGEK – A VÍZRAJZI OSZTÁLY
189 4/5 ÉVI FÖLVÉTELEI SZERINT – A BALATON KÖZÉPVÍZSZÍNÉRE VONATKOZNAK,
MELY VÍZSZÍN AZ ADRIAI TENGER SZÍNE FÖLÖTT 104.52 MÉTER MAGASSÁGBAN
VAN: Water depths – according to the measurements of the Dept. for hydrography in the years
1894–1895 – are measured from the mean water level of Lake Balaton, which is 104.52 meters
above the water level of the Adriatic Sea
Fig. 8. Cutout of the 1895 bathymetric map, showing measurement points with depth labels, bathymetric contour lines, railway line with station, church tower (landmark), fixpoint and
tributary
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Fig. 9. Photograph of the elevation benchmark on the wall of the “Round Chapel” near the
shore in Balatonfüred. Inscription of the bronze plaquett: Vı́zrajzi magassági jegy: Hydrographic
elevation mark (in Hungarian)
Results
The main objective of the processing of this map was to measure sediment accumulation processes in the lake and other changes in the bathymetry. As Lake
Balaton is very shallow, the accumulation of sediment arriving from the Zala River
is a cause of concern ever since the lake is used for recreation. The measurement
points shown on the map were digitized with the water depth saved as an attribute,
and the elevation of these points above sea level was calculated by subtracting from
the elevation of the mean water level. The shore line was also digitized, and its
points were added to the measurement point set with an elevation corresponding to
the water level of the lake. A digital elevation model was interpolated from this 3D
point set using Golden Software Surfer 8. The uneven spacing of the measurement
points is in agreement with the uneven relief of the lake floor and so is suitable for
drawing a bathymetric map by hand, but causes major problems for mathematical interpolation. Several methods were tried, and the most satisfying results were
obtained by Natural Neighbor interpolation with an anisotropy of 1.5 in the direction of the axis of the lake. This applied interpolation method smoothed anomalies
caused by the measurement sections perpendicular to the shore, but enhanced them
on the short stretches of the shore which were not in the main direction of the lake
(Fig. 10). This depth profile is remarkably similar to the present-day depth profile
of the lake. We created a grid of the same cell size by resampling the digital elevation model of the latest bathymetric survey of the lake which was carried out in
1975 (Sass 1979), and created a new grid by point-by-point subtraction of the elevaActa Geod. Geoph. Hung. 44, 2009
BATHYMETRIC MAPS OF LAKE BALATON
93
Fig. 10. Depth-shaded bathymetric Digital Elevation Model of Lake Balaton based on measurement points of the first bathymetric survey. Scale bar shows elevation above sea level. Inset shows
the effect of anisotropy applied on interpolation
tions of the cells of the 1895 grid from the 1975 grid. The resulting dataset showed
that on this spatial scale no considerable change has happened in the elevation of
the lake floor during this period of 80 years. Although this was not a quantitative
examination — which would be impossible due to the small number of measurement points on the 1895 map — it suggests that the concern about the sediment
accumulation of Lake Balaton is not necessarily based on scientific evidence.
Conclusions
Maps produced in Hungary in the late 18th and 19th century have a spatial
relevance that allows for georeferencing with an accuracy that is comparable to the
errors of the original surveying methods. Nowadays, efforts of nature conservation
are focusing more and more on recreating the original, natural state of protected
areas based on state-of-the art scientific evidence. Information about natural vegetation, land use practices and even bathymetry in times before industrialization
can be utilized for planning restoration efforts.
The Krieger map shows a detailed depiction of agricultural and natural areas
around the lake, which can now be exactly localized because the map is georeferenced in full detail. The 1895 bathymetric map can be used as input data for
modern GIS-based bathymetry studies (Table I).
Acknowledgements
The Krieger map was provided by the archives of County Zala, scanning was generously
provided by the Department for Cartography and Geoinformatics of the Eötvös Loránd
University, Budapest. The published copy of the 1895 bathymetric map was kindly scanned
and provided by the library of the Hungarian Geological Institute. D Ligeti is thanked for
correction of our translations from Latin.
This work was supported by the Hungarian Scientific Research Fund, project
number T47104.
Acta Geod. Geoph. Hung. 44, 2009
94
A ZLINSZKY and G MOLNÁR
Table I. The basic attributes of the Krieger and the 1895 bathymetric map
Year
Geodetic datum
Coordinate system
Horizontal unit
Vertical unit
Bathymetric contours
Measurement points
Shoreline
Shore land use
Shore relief
Basis of georeferencing
Method of georeferencing
Krieger map
First bathymetric survey
1776
local
unknown local
Viennese fathoms
Viennese fathoms
1, 2, and 3.5 fathoms
unknown
(except deepest point)
mapped
mapped
hachured
settlements, landmarks
linear
1895
Buda 1863
stereographic
Viennese fathoms and kilometers
meters
1, 2, 3, 4, meters
2884 measured,
1310 points mapped
mapped
not mapped
not mapped
benchmarks, buildings, railway
coordinate registration,
(correction by triangulation)
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