terrestrial laser scanning for the visualization of a ... · 31.92” e ina rock-wall...

Photogrammetrie • Fernerkundung • Geoinformation 4/2009, S. 329–339

DOI: 10.1127/1432-8364/2009/0025 1432-8364/09/0025 $ 2.75© 2009 DGPF / E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart

Terrestrial Laser Scanning for the Visualization of aComplex Dome in an Extreme Alpine Cave System

Manfred f. Buchroithner, Dresden & thoMas Gaisecker, horn, Österreich

Keywords: Cave Surveying, 3D Visualisation, Dachstein, Karst Hydrology,Terrestrial Laser Scanning

pacity and to model both seepage/percolationand run-off.

Moreover, caves allow geologists and inparticular structural geologists, to combinescarce and often vague surface evidences con-cerning the geological structure of mountainswith explicit and indicative subterraneous ob-servations to a clear(er) three-dimensionaltectonic development model of the respectivearea. This applies especially to the DachsteinMassif where mighty layers of carbonaticrocks have been thrusted over the metamor-phic clastites of the East-Alpine GreywackeZone (Buchroithner 1993).

1 Motivation and Location

Being the most valuable resource of the 21st

century, water – and in particular potable wa-ter – is gaining increasing importance, also inresearch. In the Alps and world-wide the cal-careous karst mountains are the main bearersof underground water. Therefore it is certainlyof high interest for karst hydrologists and,hence, speleologists to obtain detailed infor-mation about shape and volume of the cavitiesinside the limestone mountain ranges. This al-lows to get a grip onto their water storage ca-

Summary: The 3D surveying of two big cavitieswith very complex shapes in the Dachstein South-face Cave, Styria, Austria, serves as an example todemonstrate the efficiency of exact coordinate reg-istration in caves by means of laser scanning. Thesurveyed cave is not open to the public and classi-fied as difficult. The complicacy of a suggestivevisualisation of such complex cavities is shown us-ing the so-called Ramsau Dome as an example.Digital animations are considered the only possi-bility to adequately visualise such cave systems.During a surveying campaign of several days theRiegl Z-420i laser scanner worked reliably as dataacquisition instrument despite the extreme condi-tions regarding temperature, air humidity and dirt.The generated point cloud models represent thepresently best data bases for application modellinglike for well discharges in karst hydrology and pho-to-realistic visualisations.

Zusammenfassung: Terrestrisches Laserscanningzur Visualisierung eines komplexen Hohlraums ineinem extremen alpinen Höhlensystem. Am Bei-spiel der Vermessung von zwei mächtigen undformmäßig komplexen Hohlräumen in der Dach-steinsüdwandhöhle, Steiermark, Österreich, wirddas Potential für deren Formerfassung mittels La-ser-Scanner erläutert. Die Höhle ist nicht für dieÖffentlichkeit zugänglich und gilt als schwer be-gehbar. Anhand des so genannten Ramsauer Domswird die sehr schwierige graphische Darstellungsolch komplexer Hohlräume demonstriert und alseinzige Möglichkeit für eine adäquate Visualisie-rung die digitale Animation erkannt. Der einge-setzte Laser-Scanner Riegl LMS Z420i hat sichunter extremen Bedingungen hinsichtlich Tempe-ratur, Luftfeuchtigkeit und Schmutz während desmehrtägigen Einsatzes als Datenerfassungsinstru-ment bewährt. Die letztendlich entstandenenPunktwolkenmodelle stellen die bislang besten Da-tengrundlagen für verschiedene Applikationsmo-dellierungen, wie z. B. für Quellschüttungen in derKarsthydrologie und fotorealistische Visualisie-rungen, dar.

330 Photogrammetrie • Fernerkundung • Geoinformation 4/2009

statements by the first author formulated bySchön 2007a, 2007b).

Moreover, the application of modern 3Dsurveying techniques like 360° rotational la-ser scanning to very complex cave systemshad been another challenge. Their outcomemight be expected to serve the visualisation ofthe complex best. Hence, one of the major mo-tivation aspects of another 3D cave surveyingcampaign (cf. Section 4) was the attempt toachieve adequate measurements for a close-to-nature optimised geovisualisation. Sincedifferent textures and colours do not play thatbig a role in this pure limestone cave, prioritywas given to the mere extraction of the caveshape, and no photographs were acquired si-multaneously.

The entrance of the DSFC is located rightbelow the prominent peak of Hoher Dachstein(2995 m), at 47° 28’ 00.85” N and 13° 36’31.92” E in a rock-wall called Mitterstein (cul-

Based on our present knowledge of theDachstein South Face Cave (DSFC) the ideasounds both intriguing and plausible that deepin the mountain the cave might intersect alongthe aforementioned thrust-plane, thus allow-ing not only a visual inspection of this majortectonic feature of the Alps but also the possi-bility of quantitative subterraneous measure-ments.

A particular appeal and challenge for theexploration of the DSFC is the expectationthat possibly the connexion between the DSFCand the complex cavity system of the HierlatzCave System on the northern side of theDachstein Massif, which has already beenproved by tracer experiments, may one day becrossable, i. e., climbable, by men. Such an ex-treme traverse under the whole massif of theDachstein Mountains would then representone of the most adventurous and hugest spe-leological enterprises in the world (cf. also

Fig. 1: Digital terrain model of the Dachstein Massif, view towards northwest, in the near rangerepresented as a triangular network draped with a geo-coded Landsat TM imagery viewed againstthe Dead Mountain Range in the background. In the upper left corner the position of the DachsteinSouth Face Cave (DSFC) can be seen through the wireframe of the relief model. For location ofcave entrance in map see Fig. 2. 4 mm left the Ramsau Dome.

M.F. Buchroithner & T. Gaisecker, Terrestrial Laser Scanning 331

scanning in order to survey some of the biggerhalls in this complex cave system which is,moreover, comparatively difficult to climb.

2 Previous Surveys

Already in 1910, the Moravian speleologistIng. Hermann Bock, his wife and companionsset out from Graz and made a first survey ofthe outer parts of the DSFC, which was dis-covered by the Dachstein mountain guide Jo-hann Knauß in 1886 and even earlier by localhunters, and published in 1913 a first simplesketch-map up the famous Ramsau Dome.One-hundred years later, in 1986, the Salz-burg-based karst hydrologist W. Gadermayrand companions performed an uranine tracerexperiment at a spring between Bivouac 2 and3 and also produced a new map (Graf 1996).Based on these advance efforts in the sameyear a first surveying reconnaissance trip intothe cave until close to Bivouac 3, i. e., behindthe Schladming Dome, was carried out byFritz Ebner, Mining University in Leoben,Austria, Anton Streicher, Vice Mayor of theCity of Schladming and head of the Cave Re-search Group in Schladming, Austria, and thefirst author. The years 1996 to (spring of) 2007

minating at 2122 m) in 1834 m at the foot of themighty, almost 900 m high and roughly 2900 mwide Dachstein South Face. It can only bereached by climbing. From the end of thecurvy Dachstein Road at 1710 m a mountaintrail, passing the Dachstein South Face Hut(1910 m), leads close to the Mitterstein rockface where a one-pitch rock climb allows toreach the cave entrance (cf. Fig. 1 and 2). Theposition of the “Dachstein Hole”, as it is calledby the local population, is illustrated in Fig. 1.The cave is indexed in the Austrian Cave Cat-alogue under Code No. 1543/28. Its exploredextension under the Dachstein at the end of2007 is shown in Fig. 2.

Due to the initiative and the repeated invita-tion of the Cave Research Group of the Schlad-ming Chapter of the Austrian Alpine Club(OeAV), in 1996 (Graf 1996) the first authorof this paper and a group of venturesome stu-dents from Dresden started a series of surveycampaigns in the DSFC. Their intention wasto obtain a three-dimensional cave model byconventional geodetic measurements. In orderto achieve this, a traverse with frequent cross-sectional measurements has been surveyed,an undertaking of extreme hardness. This fi-nally resulted in the Dresden proposal to testthe advanced technique of rotational laser-

Fig. 2: Depiction of the complex system of the Dachstein South Face Cave (as explored until theend of 2006) in between a wireframe representation of the relief and a reproduction of a part of the1 : 25 000 sheet “Dachstein” of the Alpenverein Map Series, Edition 2005. The vertical red spikerepresents the famous Schladming Shaft which reaches a height of at least 150 meters and whichwas also measured by laser scanner during the described campaign.


Dresden speleology groups. Moreover, car-tography students of the Dresden Universityof Technology were employed as porters fornutrition and gear along the small trail up tothe cave entrance. Last but not least the laserscanner weighing some 16 kg incl. wrapping,the laptop, several smaller lead-acid batteries(cf. Section 4) and the tripod had to be carriedinto the cave – and finally back out!

The whole surveying campaign was real-ised under extreme circumstances regardingboth the accessibility of and the rock-climbingdifficulties in the cave: So the way back fromthe bottom of the Schladming Shaft, a near-vertical cavity of some 12 m in diameter andapprox. 150 m in height requires about 60 m ofjumar-ascending on a freely suspended rope.Moreover, constrictions barely wide enoughto squeeze the laser scanner (cf. Figs. 2 + 3)through them had to be negotiated.

Thanks to the cooperation with the caversfrom Schladming a nearly horizontal suspen-sion rope-bridge of 9.4 m length (calculatedusing the Riegl RiPROFILE® post-processingsoftware) had been installed in the RamsauDome in order to facilitate movement in thispart of the DSFC (cf. Fig. 4, 6, and 9). Previ-

saw seven multi-day cave expeditions jointlyperformed by the Institute for Cartography ofthe Dresden University of Technology (TUD),the Cave Explorer Group from Landshut, Ba-varia, and naturally the aforementioned caversfrom Schladming. Within these years theDSFC was measured using traditional survey-ing-equipment, i. e., theodolite and suspensioncompass, in the manner described above (cf.Section 1). A short speleological history ac-count by VHO (2008) is also accessible underwww.hoehle.at/deutsch/SuedwandGeschichte.htm.

As an outcome of these operations, apartfrom a final internal surveying report of theInstitute for Cartography of the Dresden Uni-versity of Technology written by Graf (1998)and a comprehensive diploma thesis about thedetailed 3D modeling and animated carto-graphic visualization of the – at that time sur-veyed parts of the – “Dachstein Hole” byteichmann (1999), two popular-scientific edu-cational films about the activities of the Dres-den Group were published. These films of 18and 36 minutes length respectively were sev-eral times on the programs of various TVchannels, thus very well documenting the sur-veying methods used for the public. Usingthese methods, the measuring of extremelybig cavities with adequate precision was ratherunrealistic. To get a more detailed 3D-modelof these halls the first author of this paper de-cided to make use of the advantages of laser-scanning.

3 Campaign Logistics

In the winter semester 2006/07 speleologistsfrom Bad Mitterdorf in Styria, Austria, to-gether with 8 cavers from Dresden undertooka big combined surveying campaign of 10days under the leadership of Robert Seebach-er, Bad Mitterdorf, and the first author. Thisenterprise which comprehended the surveyingof both, the so-called Ramsau Dome and theSchladming Shaft, and an advance to the mostdistant parts of the cave system, some 8.7 kmaway from the entrance, required an intensivepreparation and complex logistics. The latterones included precursors to this event per-formed by both the Bad Mitterndorf and the

Fig. 3: At the lower end of the 60 m-rappelthrough the nearly vertical Schladming Shaft.Note the caving pack containing the60 cm×40 cm×25 cm wrapping and the laserscanner which is all in all weighing approx.16 kg.


Moreover, the decision to use this scanner in-stead of a phase difference scanner was trig-gered by the fact that the very model had al-ready previously been successfully used forthe scanning of open pits and constructed tun-nels. Riegl Corp. also welcomes another testof their LMS Z420i under extreme condi-tions.

Despite the exceptional circumstances re-garding temperature, air humidity, argilla-ceous dirt and dripping water, the instrumentdemonstrated in these harsh situations its out-standing qualities with respect to robustnessand usability. Fig. 3 documents a typicalclimbing situation during the scanner trans-portation inside the cave, and Fig. 5 shows apicture taken during the work with the laserscanner in the Ramsau Dome.

The scanner can be manually tilted in 5-de-gree steps to guarantee a full 360°×360° fieldof view. Fig. 4 illustrates this and all the otherfeatures described in this paragraph (cf. Num-ber 1 in Fig. 4). The system is complementedby a data acquisition system based on a stan-dard laptop (3). Data acquisition, sensor con-figuration, data processing and storage areoperated by the companion software RiSCANPRO®. The scanner is mounted on a standard

ously, it had only been possible to proceed byrappelling 11.5 m to the base of the dome onone side and ascending the other one by diffi-cult rock climbing. In any case, to reach theSchladming Shaft, first 17.3m have to beclimbed on a free-suspended rope by jumar-ascending. This is, above all, an interestingstatement that corrects the passed-on overesti-mation of the cavers that you have to negotiatea vertical distance of 20 m plus. (All distancescalculated using the Riegl RiPROFILE® soft-ware).

4 Laser Scanning

As already mentioned, it was unrealistic tomeasure the extremely large cavities insidethe DSFC by using the described traditionalmethods. In order to get a more detailed 3D-model of these cavities the first author decidedto use a Riegl LMS Z420i laser scanner (cf.Fig. 4). Its technical specifications can be ob-tained from the product information providedby Riegl Laser Measurement Systems. Thewhole system is battery-powered and easilyportable, but yet robust and operable under awide range of environmental conditions.

Fig. 4: Operating the Riegl LMS Z420i at a rock pulpit in the Ramsau Dome. Location cf. Fig. 2. Forexplanation of the figure see text above.


tion of the scanner guarantees a maximumprecision and accuracy for the target measure-ments. The resulting coordinates are stored inthe scanner’s own coordinate system. To reg-ister a scan position into global coordinates itis necessary to calculate the correct transla-tion- and rotation matrix which was also doneby means of the aforementioned software.

If a minimum number of only three targetsis available, the matrix is calculated fully au-tomatically by finding corresponding pointsbetween the scanner’s own coordinate systemand the given global coordinates. The algo-rithm which is used to find the correspondingpoints compares all 3D distances between thetargets. In this case the user can mount thescanner in any orientation. In principle thescanner can be also mounted over a ground-control point and leveled by means of the laserscanner’s inclination sensors. One visible tar-get is enough to calculate the correct bearingangle. This workflow, called “backsightingorientation”, however, turned out to be not ap-plicable under the narrow conditions insidethe cave.

RiSCAN PRO® also allows registering thepoint-cloud of a certain scan position by justusing overlapping scan areas of an alreadyregistered scan position. This workflow is notlimited to two scan positions, it can be run ona number of different scan positions at thesame time. The algorithm (the so-called ICPalgorithm, BeSl & mcKay 1992) works itera-tively and detects the closest point of the otherpoint-clouds for each point in a point-cloud.The adjustment iteratively modifies positionand orientation information of each scan posi-tion until the error reaches a minimum.

All these registration tasks deliver results ofjust a few millimeters of standard deviation.The overall accuracy (geo-reference) dependson the precision of the given ground controlpoints (cf. above).

5 Visualization of SurveyingResults and Derivates

After the registration at each scan station theprimary output delivered is one combinedpoint cloud for each of the surveyed huge cav-ities (halls, domes), representing a sampled

surveying tripod (2), power supply can be re-alized by any power-resource between 12 and28 voltage. Inside the cave special light-weighted battery-packs were used (4). Thelaptop was also running on these batteries.Recharging of the battery-packs was realizedby using a generator-station located in the“base-camp” at the cave entrance.

Marked ground-control points already pre-cisely measured in both directions (inboundand outbound) by measuring tape and ana-logue theodolite during previous campaignswere used to obtain the correct orientation ofthe point-cloud acquired by the scanner, with-in the global coordinates. Special fixing equip-ment was used to guarantee an exact positionof the reflector targets. Despite the high hu-midity no difficulties occurred with the signalreflection.

Five 360° high-resolution scans with 12000points were acquired on each side of the basalcanyon (cf. Fig. 4, 6, and 9). In order to obtainnear-realtime point-cloud visualisations of themeasured surfaces – last not least for qualitycontrol and the detection of concealed spaces– Riegl software was used, too. The compan-ion program systems RiSCAN PRO® and thepost-processing tool RiPROFILE® enabled anautomatic registration of the acquired point-clouds using a minimum of three but mostlyfour targets. This allows skipping the levellingof the scanner and the measuring of the scan-position to a degree of sub-minute accuracy.RiSCAN PRO® and RiPROFILE® automati-cally detected the targets because of their highreflectivity. Due to the complexity of theirshape and the resulting occluded surface por-tions, in the Ramsau Dome as well as in theSchladming Shaft measurements at severalscan positions and with different tilting anglesat each position had to be carried out.

Using control points measured in a tradi-tional geodetic way (accuracy some millime-ters) each point cloud, acquired from differentscan positions, was then automatically regis-tered into the given global coordinate system.In a first step the global coordinates of theground control points were imported as ASCIIinto RiSCAN PRO®. For each scan-positionthe scanner detects all visible ground controlpoints because of the high reflectivity of thereflector targets. The highest possible resolu-


Fig. 5: Illustration of an ~ 200° sector of the point cloud of one single rotational laser scan showingthe rock pulpit (“plateau”) where (the former) Bivouac 1 is located below the rock face in the back-ground (cf. Figs. 7–9). Note the rope of the suspension bridge (lower left) and another fixed ropeobliquely leading some 25 m up the rock face to the cave tunnel which leads to the SchladmingShaft. Distance from viewing point to far range approx. 25 m.

Fig. 6: Visualization of a portion of the point cloud of one scan of the Ramsau Dome as seen fromnear the measuring position with relief-shaded and color-coded visualization. Distance from thereddish near range, which corresponds more or less to the position of the laser scanner in thedepicted scene, to the blue far range amounts to approx. 23.6 m. The RGB arrows indicate theorientation of the laser scanner at this scan position. Red lines correspond to the ropes of a sus-pension bridge erected for easier crossing of the basal canyon of the cavity.


replica of the objects’ surface (cf. Fig. 6). Tri-angulating the point-cloud results in a 3D sur-face model (cf. Figs. 6, 8, and 9), this modelcan then be used for further post-processing:volume calculation, contouring and horizontalas well as vertical and horizontal profiling (cf.Fig. 7) can easily be performed.

The total height of the dome is approx.46.9 m, its maximum horizontal diameter 28.1m. Its volume amounts to 325 m³. This calcula-tion is based on the fact that some remaininguncovered patches of the irregular surface ofthe cavity have simply been closed by an ap-proximating algorithm (see below). Hence,this figure represents a minimum value.

The impossibility to make extrapolationsfor surface portions not shown in the pointclouds prevents to close holes subject to deadcorners/blind spots by methods commonlyused for geometrically well-defined objects inurban environments (e. g., SchnaBel et al. 2006cum lit.). Here, the use of methods based onBézier splines like NURBS led to acceptableresults. It has, however, to be kept in mind that– in contrast to anthropogenous objects – prin-cipally these interpolations represent solutionsvoid of any proximity to reality. In any case,the closed point cloud models outweigh by far

Fig. 7: East–West trending vertical cross-sec-tion through the Ramsau Dome showing 1 mcontours in red. Black coordinate lines corre-spond to the vertical rotation axis of the differ-ent visualizations of the cavity and the inter-nally defined “zero level” of the laser scanningcampaign. The total height of this cavityamounts to 47 m (which cannot be displayed inone vertical section though). On the right is therock pulpit of Bivouac 1 at a height of some11 m above the bottom (cf. Figs. 4 + 8).

Fig. 8: The individual figures show color-coded views from 4 different directions into the slit cavityof the Ramsau Dome. Apart from animated visualizations, possibly such multiple illustrations rep-resent the best possible way of conveying an impression of the complex shapes of such cavedomes. Spectral color-coding in this and the following figure is not to scale but adjusted to therespective maximum range.


6 Assessment of Results

Until present time laser scanning has been fre-quently used for the three-dimensional surfacedocumentation of cultural heritages of differ-ent size such as architectural, archaeologicalor natural ones (cf. herdt & JoneS 2008, Pet-titt et al. 2007, Birch 2008, www.stonepages.com/ news/archives/ 000757.html, KerSten etal. 2009, notheGGer & dorninGer 2009).

Caves have mainly been surveyed by 3D la-ser scanning if their access and their “walka-bility” were comparatively easy (cf. fryer etal. 2008, www.high-pasture-cave.org/index.php/news/comments/ 168/), as it is usually thecase with caves affiliated to mines (which aremostly easily accessible; cf. the Cueva de losCristales near Naica, Mexico, a site connectedto mining shafts; www.faro.com/ content.aspx?ct=ge&content=news&item=14; caneveSe etal. 2008) and with natural tourist caves whichare open to the public. Actual “research caves”which are only climbable for speleologists

the previous results made with bump-mappingtechniques draped on TIN models which weregenerated by the “classical” surveying meth-ods described above (cf. teichmann 1999).

Comparisons between laser distometermeasurements of the distances between poly-gon points of previous surveys and the corre-sponding distances acquired during the laserscanning campaign showed practically no de-viation, i. e., less than 2 cm. The absolute ele-vation of the afore mentioned suspended rope-bridge in the Ramsau Dome amounts to1780.4 m asl (WGS84). This statement is pos-sible due to the fact that the interior measure-ments within the DSFC were linked to previ-ously surveyed points tied to the National Ge-odetic Network of Austria. It corroborates thepreviously made relative vertical measure-ments, which indicate a 60 m descent from thecave entrance.

Fig. 9: Top-down view (radial color-coding from central axis into the Ramsau Dome). The sus-pended 9.4 m long rope bridge over the basal canyon with its wirings can be clearly seen.


stone massifs, and hence possible dischargerates of karst wells.

With respect to a visualisation which allowsthe viewer of “flat” (i. e., non-autostereoscop-ic) depictions to obtain a realistic conceptionof the respective complex cavities, however,one has to state that the only means providingan adequate picture of the shapes is a digitalanimation. Even a series of different cross-sections and colour-coded oblique views fromdifferent directions (see above, in particularFig. 10) cannot be sufficiently suggestive ofthe physical shape. In this respect electronicvisualisation means are clearly superior tohardcopy displays. At this point the animationof the High Pasture Cave published by Birch

(2008) in the digital version of Past Horizonshas to be seen as one of, if not the first reason-able example.

Acknowledgements

The strong support of Robert Koschitzky,Dresden University of Technology (TUD),and his devoted team of Dresden hobby spe-leologists during the preparatory phase of thesurveying campaign and during the field-workis highly appreciated. Robert Seebacher, inter-nationally renowned speleologist and head ofthe Cave Research Group in Bad Mitterdorf,Styria/Austria, kindly assisted with his wideexperience in both the mission planning andthe further surveying of the Dachstein Hole.Anton Streicher, Deputy Mayor of the City ofSchladming, Austria, provided substantial in-frastructural, logistic and financial support.Bernd Hetze, Centre for Information Technol-ogy Services and High-Performance Comput-ing of the TUD, kindly assisted in the dataprocessing for Fig. 1 and 2. For all other fig-ures depicting the point clouds of the laserscanning results Thomas Himpel from the In-stitute for Cartography of TUD has to bethanked. Finally, without the generous provi-sion of the LMS-Z420i 3D scanner throughRiegl Inc., Horn, Austria, the whole projectcould not have been carried out at all. Further,the critical reading of three unknown review-ers significantly improved the quality of thisarticle.

have, so far, only rarely been surveyed bymeans of laser-scanners. To the authors’knowledge, the second-largest cave chamberin the world at Majlis Al Jinn in Oman hasbeen surveyed using a laser scanner. This hall,however, is “easily” accessable by “simple”rappelling over a distance of 150 meters (www.youtube.com/watch?v=QgDHTDQp8Q0).There, neither creeping through super-narrowbottlenecks nor climbing is required. Also interms of visualisation of complex naturalcaves, so far almost exclusively simplifiedbox-shape representations have been pub-lished (cf. www.esri.com/industries/cavekarst/graphics/karst_ro_bg.jpg).

Hence, the surveying reported in this paperto some degree represents a premiere. Cer-tainly, the transportation of a terrestrial laserscanner of the quality and weight of the RieglLMS Z420i both through a bottleneck whichwas barely big enough to squeeze the laserscanner through and over a freely suspended60 m rappel-and-ascend pitch with drippingwater is a rather unique undertaking.

7 Conclusions and Outlook

In conclusion, the described cave surveyingcampaign, which was from its beginningmeant to serve as a test operation, well dem-onstrated the feasibility of the used methodol-ogy and also of the utilised laser scanning de-vice for the three-dimensional measuring ofcomplex irregular cavities of medium to largesize (up to several tens of meters) with fre-quent dead spots. The instrument, accordingto the producer’s fact sheet dust- and splash-water-proof, turned out to be also reasonably“mud- proof“.

Future operations of this type will – person-nel with adequate scientific and technicalbackground and alpinistic and speleologicalskills provided – certainly be able to serveboth the purpose of solving tectonic under-ground conditions and of quantifying theshapes and volumes of subterraneous cavities.This, again, allows to acquire informationabout the genesis of particular karst caves andto come closer to a quantitative model of karst-water behaviour, and thus to better estimatesof the “porosity” and storage volume of lime-


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Addresses of the Authors:

Prof. Dr. phil. habil. manfred f. Buchroithner,Technische Universität Dresden, Institut für Kar-tographie, D-01062 Dresden, Tel.: +49-351-4633-7562, Fax: +49-351-4633-7028, e-mail: [email protected]

Mag. Thomas GaiSecKer, Riegl Laser Laser Measu-rement Systems GmbH, A-3580 Horn, Riedenburg-straße 48, Österreich, Tel. +43 2982 4211. Fax +432982 4210, e-mail: [email protected]

Manuskript eingereicht: Januar 2009Angenommen: April 2009

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