UDC 341.222.001(497.12/.13) 
REGULARIS~ ON F INTER-
NATIONAL BOUNDARY LINE 
BETWEEN SLOVENIA AND 
CROATIA 
Božo Demšar 
MVOUP-Republiška geodetska uprava, Ljubljana 
Received far publication: Nov. 17, 1992 
Abstract 
Described and based with argumenti· is a suggestion fara 
boundary survey of a course of the international boundary line 
between Slovenia and Croatia by the virtue of valid 
documentation of the Republican boundary line in ex Tugoslavia. 
Keywords: cartographicbase, Croatia, history, international 
boundary line, land ownership boundary, organization, 
procedures, Slovenia 
INTRODUCTION 
By Slovenia's attainment of independence and statesmanship, the international boundary between the ex Republics of Yugoslavia, Slovenia and Croatia, has been 
reinstated. By the basic constitutional document ofthe attainment and autonomy ofthe 
Republic Slovenia (Official Gazette ofthe Republic ofSlovenia- Ur.l. RS No. 1-4/91) 
Slovenia has acknowledged international boundaries ofthe ex Socialist Federative 
Republic ofYugoslavia (SFRJ) with Austria, Italy, and Hungary, and the boundary 
between the Republic Slovenia and the Republic Croatia within the ex SFRJ. Both new 
states have declared on intemational level that they do not have any territorial 
pretensions, and that they respect the existing mutual Republican boundaries. 
THE BOUNDARY LINE OF THE REPUBUC SLOVENJA WITH ITALY, AUSTRIA AND 
HUNGARY 
The boundary line of the Republic Slovenia with Italy, Austria and Hungary was defined, marked on terrain and documented as the international boundary line of 
Yugoslavia. The boundary documentation comprises also the whole surveying 
documentation of the land survey of the course of the international boundary marked 
with numbered boundary stones, a detailed situation of bounda,ry stones, a detailed 
area boundary survey, and a trigonometric planimetric and altitude network. The 
whole documentation of the international bounda.ry of the ex Yugoslavia and also of 
Slovenia is kept at the ex Federal Foreign Office, which was in charge of affairs 
concerning international boundaries. In the execution of the international boundary 
survey the ex Foreign Office cooperated with the Military Geographic Institute in 
Belgrade and with the Hydrographic Institute in Split. 
eodetski vestnik 36 (1992) 4 
Slovenc Rcpuhlican Survcying and Mapping Administration has managed to 
some parts of documentation on the international boundaries in form of 
copies, yet these as such are not in force. The data on the international boundaries 
were inau·essihlc to puhlic. For this reason they were harcl to get to ancl this only for a 
spccific aim. The so far though informal talks with survcying offices in neighhoring 
statcs are vcry promising as to ohtaining from them without too many difficulties thc 
official data on the international houndaries. In spite of this it is neccssary to ohtain as 
soon as possible data on international boundaries and other surveying data for the 
tcrritory of Slovcnia also frnm the archives of the ex Yugoslavia. Thesc data are 
important for research work and are part of SI ovene national and precious archival 
material. Tn this task a larger group of cxperts frorn various professional fields ofwork 
will havc to cooperate with thc Slovene Foreign Of!ice. 
THE IWUNDARY LINE OF THE REPUBLIC SLOVENIA WITH nrn REPUBUC CROATIA 
boundary line of the Repub!ic Slovenia with the Rcpublic Croatia was dcfined 
nccnrcling to legal provisions about dividing the Peoplc's Republic Slovenia 
to towns, districts, and communes (Official Gazette of the Socialist Repuhlic of 
Slovenia - Ur.!. SRS No. 11/52 and amendments 9.7.1982), and hy thc Article 7 of thc 
Law on Procedures for a Foundation, Integration e.g. a Change of Territory of a 
Commune (Ur.!. SRS No. 82/80), which determine territories of communes with 
territories of cadastral communes. In equal general terms the coursc of the 
Repuhlican houndary was defined in Croatia hy the Article 4 of thc Constitution of 
the Socialist Republic of Croatia: The territory of the Socialist Republic of Croatia is 
composed of tcrritories of communcs defined by law. The territory of the SR Crnatia 
is an integral part of the territory of the Socialist Federative Republic of Yugoslavia. 
The boundaries of the Socialist Republic Croatia may he changed only by the virtue of 
law of the parliament of the SR Croatia, and in accordance with the expresscd will of 
the inhahitants affected by the change. The territory of communes in Croatia was 
defined hy Law on Territorics of Communes and Arondisscments in the National 
Repuhlic of Croatia (Official Gazette - NN 39/62). Consequently, the external 
boundarics of cadastral communes towards Croatia and vice versa form at thc same 
tirne also Republican houndary line hctween Slovenia and Croatia within the ex 
Yugoslavia, which hoth Repuhlics, resulting from the understanding of the attainment 
declaration, acknowledge. The detailed ascertaining and marking houndaries of 
cadastral communes is in hoth Rcpublics regulated by Law on Boundary Survey e.g. 
Law on Land Cadastre. 
From the above said we can s tate that the boundary in ex Yugoslavia between Slovenia and Croatia was defined and documented by official land cadastre maps 
of both republics and by the documentation of ascertainment and delimitation of 
boundarics of cadastral communcs, although today on terrain the boundary marks no 
longer exist. Eventual later mutually agreed on and correctly on the repuhlican leve! 
acknowlcdged changes of boundaries of bordering cadastral communes remain to be 
ascertained. The international houndary on land betwecn Slovenia and Croatia will 
therefore not be defined on terrain asa new horder on the basis of international 
princip les and regulations by taking into consideration natura! boundaries of rivers 
and other in nature characteristic lines or political international agreements as it 
Geodetski vestnik 36 (1992) 4 
usually was the casc in history in defining houndaries among states. The international 
boundary has to be ascertained on terrain, delimitated on the course of the current 
republican boundary on the basis of the documentation of this boundary, which are 
valid land cadastral maps. Corrections on terrain so ascertained boundary to the 
natura! boundary may then be the issue for an agreement between the two states. The 
boundary at see which has so far not been defined, has to be defined anew. A very 
important starting-point for defining the boundary at see is the fina! point of the land 
boundary, and because due to small area of the Slovene sea probably also very 
important and decisive is functionality of the territorial Slovene see. Due to given 
cartographic foundation of the houndary and its technical characteristics, an 
agreement hetween Slovenia ancl Croatia is neeclecl and in all particulars preparecl 
regulation ahout the mode and technology of the execution procedure of asccrtaining 
and clelimitation of the ex repuhlican ancl now international boundary between 
Slovenia and Croatia is also needed. 
CARTOGRAPHIC BASIS OF THE BOUNDARY COURSE WllTH THE REPUBUC CROATIA 
The detailed land cadastre survey for the territory of Slovenia was executed in years 1818 till 1829; til! 1864the Janci cadastre maps were renovatecl (reambulated), and 
graclually till 1890 used for the set up of the land register for lancl ownership records 
keeping and were also in use as the basis for agriculture tax assessment (fiscal,. tax 
cadastre). After 1890 the cadastral records are regularly maintained hy the surveying 
service. Land cadastral maps for the lerritory of Croatia were macle la ter from 1853 
till 1863 hy the same technology and procedures. 
The territory of a cadastral commune comprised land property of settlement inhabitants, which was included in individual cadastral communes. The 
clelimitation procedure was regulated by „Instructions for County Land Survey", 
issued in 1824 for the ex Austria-Hungary. The boundary line of a land cadastre 
eommune was delimitated by numbered boundary stones; about the clelimitation a 
detailed description was made. Unfortunately, the majority of cadastral stones is 
ruined. The whole documentation was carefully stored; when making use of the maps 
special care was taken not to damage any maps. During World War II much was 
destroyecl and after 1945, due to inattentiveness much damaged and lost, whereas the 
wholc clocumentation for the territory of Slovenia was not even taken into posses.sion 
from the archives of the ex Austria-Hungary. 
ASCERTAINMENT AND DEUMITATilON OF THE iNTERNATIONAL BOUNDARY UNE 
terrain, the boundary line between the Republics is not marked. In practice the 
boundary was treated as an administrative boundary, the actual 
course on termin was not known, what has resulted in a series of trouble and surprises 
at the set up of a boundary regime. Above all there oceurred a difference in boundary 
course interpretation, which bas to be settled by talks on diplomatic leve!. 
The land cadastra! maps were elaborated on the basis of calculatecl and condensed graphical triangulation in Soldner Projection for the territory of Slovenia in 3 
unlinked systems. The majority of triangular points is destroyed; how many of them 
are preserved on .the boundary area with Croatia is not known. However, we did find 
eodetski vestnik 36 (1992) 4 
out that to some extent the boundary stones of the delimitation of the county 
boundary in the Ptuj Commune still exist The detailed land survey was executed using 
technology of graphical line intersections of direction to detailed points (plane table 
survey). The detail survey was executed for individual areas by sheets in each 
commune. The result is that at commune boarders, on edge comparison and on 
borders of individual areas of the detailed survey discrepancies occur. It is impossible 
to lay out individual sheets continually into a cadastral commune and cadastral 
communes can not be laid out within the area of the coordinate system. Discrepancies 
occur also on edges among coordinate systems. 
The result of the technology elaboration analysis and accuracy of the plane table survey of the land cadastre maps is that due to the stated ascertainments the 
transfer of the position of border points from a map into terrain with the calculation 
of coordinates of points by transfer into terrain, from trigonometric and surveying 
network would be - as regards tirne and expenses highly exacting piece ofwork and 
professionally unreliable, e.g. irrational, since the results would not justify the 
expenses. As we know technology of plane table survey of land cadastre maps ensures 
relative accuracy of the form, surface of parcels and position of parcels, and parcel 
boundaries form smaller areas of land table survey in the same area of the basic detail 
survey. The regulations for the maintenance of land cadastral maps of land table 
survey have foreseen a survey technology appropriate mode of maintenance e.g. 
insertion of contents of parcels' boundaries. The new parcels' boundaries or the 
transfer of the existent contents into terrain is executed by graphical coordination of 
measured parcels' situation within the frame of a divided parcel and exceptionally for 
neighboring parcels for insertion of linear objects or larger surveys. The orientation of 
the position ofparcels' boundaries are on terrain measured existing marked and 
identified ownership boundaries. On the basis of the stated issues ascertained 
accuracy, technology of additional insertion during maintenance and in practice on 
terrain, a possibility is given, in Slovenia and also in Croatia, that according to law 
land owners may find out the ownership boundaries by actual course of the boundary 
on terrain and that in a legal procedure in which the participants are land owners of 
bordering parcels. The boundary is ascertained and delimitated by signing a statement, 
which has the status of an agreement. 
In search for a mode of designation e.g. delimitation of the boundary between Slovenia and Croatia on the basis of the course of boundaries in land cadastre maps 
and taking into consideration all facts, the most appropriate delimitation of the 
boundary is to delimitate boundaries on parcel ownership criteria on the Slovene side 
of the border and ownership parcels on the Croatian side (which is at the same tirne 
the boundary of the cadastral commune and the boundary between the two states) by 
the already described procedure. The expected tolerance in use of land parcels is, 
based on experience, minimal and irrelevant and within limits of accuracy of the 
elaborntion of graphical land cadastral maps. The article deals solely with graphical 
land cadastre maps, because of the fact that at the border area with Croatia in 
Slovenia there are no maps in G. K. coordinate system, e.g. in case they should exist, 
the cadastral commune boundaries would have to be brought into line with the 
already stated regulations in·mutual understanding and on the Republic level. 
Geodetski vestnik 36 (1992) 4 
We know already that the so ascertained boundary at the course of the cadastral commune boundaries will not always be functional and practical. In such cases 
necessity will arise for coordination and mutual arguments as to the course of the 
boundary, which is to suit both sides in the grcatest possible way, e.g. will run 
according to its natural boundary. To carry out the delimitation of the boundary on 
terrain, Slovenia and Croatia are to prepare regulations in which detailed mode and 
execution procedures wiU be defined. Appropriate working commissions will have to 
be formed to conduct the boundary ascertaining and delimitation procedures. It may 
seem practical to appoint to these commissions surveying experts, operational workers 
from competent communal surveying administrations and surveying organizations. It 
will be a necessity to define a mode of dissension solutions as to the course of the 
boundary among land owners, since these dissensions among land owners must not be 
a hindrance to ascertaining boundary between two states. As to expenses, a general 
agreement is already accepted for each s tate to cany its own expenses, expenses for 
mutual work are to be shared. 
A s suggested, the boundary between the states should first be ascertained and 
fi.marked as the ownership boundary line where agreed designations would be used 
- probably in the same way as are used already. All characteristic points, an boundary 
breaking, and at the minimum distance of 250 m, should be marked by marks of an 
international bound~ry line with a current serial numberings on condition that marks 
of the international boundary line can be scen from one to another mark. Designing 
the execution we have to take into consideration that the boundary area with Croatia 
is mostly less populated and covered with dense woods, which will intensify difficulties 
on terrain work and at land survey elaboratio·n, which must be executed right after the 
delimitation. To measure boundary control points a network of order control points 
and a triangular points network at the border will have to be developed. In talks the 
Republican Surveying and Mapping Administration of Slovenia and of Croatia 
ascertained, that Slovenia possesses an improved network of trigonometric first order 
points with a network calculation with data of measured geoid points and GPS-points, 
which were measured this year in the border area in Slovenia and Croatia, by which a 
possibility was given to improve the accuracy of the network even more. It has been 
settled that the Slovenc trigonometric network, expanded in the border area with 
Croatia, will be used. Among trigonometric first order points a survey network should 
be developed. The trigonometric network project and survey network have been 
prepared by the Surveying Institute of the Republic Slovenia. 
CONCLUSION 
The Republican Surveying and Mapping Administration of Slovenia has been aware of the importance of accurate ascertainment of the boundary line between 
the Republics. So in 1970's it gathered cases where dissensions occurred and warned 
the then government about the need ofboundaries regularisation. Again in 1985 
the Republican Surveying and Mapping Administration has warned when 
misunderstandings at the boundary at Dragonja river and at other sections occurred. 
We thought it our duty to draw attention of the new government to the problems of 
the boundary; this was done already on July 11, 1990, and again on Dec. 15, 1990. 
In spite of hindrances and misunderstanding in its own ministry, the Republican 
Geodetski vestnik 36 (1992) 4 
Surveying and Mapping Administration has devoted its full attention and adequalc 
activity to questions of houndary ascertainment and delimitation. It has prepared the 
systemization for an independent group, the duty ofwhich would be the organization 
of surveying works at boundary ascertainment and delimitation, boundary line 
markings, and cooperation in working groups dealing with international boundary 
issues. It is most likely that this group is to he enlarged in a very short tirne. 
References: 
Božičnik. M.. 7987, O /(ranicama SR !-lrvatske, Geodetski list, 7,agreb, .vtev. 10-12. 329-338. 
Božičnik. M.. 1988, O /(ranicama opčina kao osnovnih dm.ftveno političkih zajednica i o 
pmblemima njihovo1; utvrdivanja. Geodetski list, Zaf;reb, ,vtev. 7-9. 259-271. 
Dem.vm; B., 1988, O republiški meji SR Slovenije, Geodetski list, Zagreb, .vtei, 4-6. 177. 
Demfar, B .. 1992. Dif;i,talizacija zemlji.vkokatastrskih načrtov. Geodetski vestnik (36), Ljuhljana, 
.vtev. l. 42-47. 
Review: Franc Černe 
Boris Premzl 
Geodetski vestnik 36 (1992)