Cadastral data play important role in many fields directly or indirectly associated with their use (land surveying, architecture and urban planning, civil engineering, agronomy forestry, transport, tourism, etc.). In forestry cadastral data mostly are used to manage forest land through the planning, protection, conservation and sustainable development. In past 10 years there are significant changes in legislation concerning the official spatial data which are also reflected on the cadastral data. Certainly two of the most important changes are the introduction of new geodetic datum and map projection, and also transition to real estate cadastre. These processes for a wide range of users will induce new investments in the transformation of existing, or acquisition of new related maps in the new datum and projection if they want to be overlaid with the cadastral data. Except the transformation to new datum and projection, in the process of transition from land cadastre to real estate cadastre it is necessary to conduct homogenization. This process is needed after transformation, for cadastral municipalities with older cadastral surveys conducted with graphical method. This process is required for solving poor cadastral plan geometric accuracy related to graphical method technical limitations. Homogenization is defined with identical points collected by the usage of Digital OrtoPhoto in scale 1:5000 (DOP5). Since Croatia is on the beginning of this kind of works, this paper examines the transformation methods of cadastral data and the optimal selection of identical point's density on the sample of cadastral district Brckovljani (Figure 1). The transformations of cadastral data were performed by the national GRID model transformation and 7-parameter transformation (Table I). For transformations control purposes, coordinates of 4 trigonometric points measured with CROPOS system (directly in new datum with specified precision of 2 cm) are used. Statistical values for the GRID transformation meet the expectations (Table 2, left), and some improvements in 7-parameter transformation (Table 2, right) could be expected if locally estimated parameters will be used. However, main problems with the local parameters are extra efforts for their district level estimation and related complications with continuity of transformations on district borders. The GRID transformation model, after it become official, seems like appropriate solution. In the process of homogenization basic principle for the selection of an identical point is its stability since the time of cadastral survey. Most of the cadastral plans (approximately 75%) are created by surveys older than 100 years, so this principle is very difficult to meet. Before the selection of identical points, 200 x 200 meters grid was constructed to support their easier selection and regular distribution. Selection is performed in 3 different densities overlaying DOP5 (density I - 0,16 IP/ha, density II - 0,07 IP/ha and density III - 0,02 IP/ha). For the control of identical point's density impact on the final results of homogenization, set of 44 control points is used. The situation with geometry of the cadastral plan before homogenization could be seen in Figure 3 and Table 3. Impact of identical point's density is evaluated comparing statistics on control points before homogenization (Table 3, right), and after this process (Table 4). Only the densest set of identical points (0,16 IP/ha) has statistical indicators better after than before homogenization. Density has crucial impact on the costs of the homogenization process but on this example it is easy to see that savings in this segment could degrade geometry of cadastral plan which is unacceptable.

In the Croatian part of the Adriatic Sea, there are 698 islands, 389 islets and 78 reefs, which make the Croatian archipelago the largest in the Adriatic Sea and second largest in the Mediterranean Sea (after the Greek’ s). Only 47 of the 698 islands are inhabited. The local economy is relatively underdeveloped, though strong expansion of tourism in the last decade stimulates it. Stronger economy growth with new infrastructural projects demands better definition of geodetic datum. Most of islands have never been unified under the same official height datum. In the course of new official geodetic datum introduction, expansion of height network on larger islands is planned. Problem of outer islands height datum definition arises. In this paper differential sea level measurement is proposed as first approximate solution. Systematic measurements of sea level in the Adriatic Sea began in 1859 in Trieste. It is interesting that the old official height datum, which is still in use, is defined as the mean sea level at tide gauge Trieste in 1875. Since this first step more than 40 tide gauge stations have been placed at the eastern part of the Adriatic Sea. These efforts had two purposes: to scientifically research the tide and to fulfil practical demands of the hydrographic survey (safety of navigation). An impressive database of sea level data measured along the east coast of the Adriatic Sea has been a base for numerous scientific researches. Sea level data of five tide gauges along eastern Adriatic Sea coast, on which new height datum is constrained, were analysed. Their time stability, differences between differential sea level measurements and geometric levelling, values of mean sea level and different geoid models fit are given. As a conclusion, usage of historical sea level data on some outer islands and new sea level measurements with sufficient time span for this purpose are suggested.

Prelaskom na novi položajni datum (ETRS89) i projekcijski referentni koordinatni sustav (ETRS89/TM ili HTRS96/TM), potrebno je transformirati i konvertirati prostorne podatke iz starog položajnog datuma (Bessel 1841) i projekcijskog referentnog koordinatnog sustava (HDKS/TM) u nove sustave. U Republici Hrvatskoj je oko 5% digitalnih prostornih podataka katastra oslonjeno na homogena polja koja su određena pomocu satelitskih metoda mjerenja. Za potrebe transformacije tih podataka u stari datum, svojevremeno su određeni parametri transformacije pomocu Helmertove sedam parametarske metode (Metoda koordinatnog okvira). Određen je cijeli niz županijskih, gradskih i drugih lokalnih parametara koji su implementirani u racunalni program Dat_Abmo, te se jos uvijek koriste kao službeni u RH. Zbog potrebe „vracanja“ prostornih podataka u ETRS89 položajni datum, koristenjem originalnih transformacijskih parametara, napravljena je analiza invertnih formula Helmertove 7-parametarske transformacije. Osim upotrebe invertnih formula, numericki su izracunani i invertni parametri (HDKS→ETRS89). Generirane su dvije rasterske mreže elipsoidnih koordinata, te je pretpostavljeno da su mreže izražene u ETRS89 položajnom referentnom koordinatnom sustavu. Testne položajne koordinate su transformirane u HDKS te potom „vracene“ natrag u ETRS89, s tri skupa originalnih i tri skupa numericki nanovo izracunanih parametara. Napravljena je analiza ulaznih i „vracenih“ ETRS89/TM projekcijskih koordinata te su prikazani rezultati.

ISO norma 19111 je prihvacena kao hrvatska norma od strane Hrvatskog zavoda za norme, a kao takva je objavljena u Oglasniku za normativne dokumente u prosincu 2008. godine. Puni naziv norme je HRN EN ISO 19111:2008 en ; Geoinformacije – Prostorno referenciranje koordinatama (eng. Geographic information – Spatial referencing by coordinates ; ISO 19111:2007). Ova norma definira geodetske referentne koordinatne sustave, datume, koordinatne sustave, složene koordinatne referentne sustave i ostale parametre koji su potrebni za određivanje prostornih podataka pomocu koordinata. Osim navedenih velicina, norma također definira postupak transformacije koordinata između razlicitih datuma, odnosno postupak pretvorbe (konverzije) koordinata između razlicitih koordinatnih sustava unutar jednog referentnog datuma. U Hrvatskoj do danas nisu jednoznacno definirani nazivi referentnih koordinatnih sustava i okvira te pripadajucih datuma (položajni, visinski, projekcijski). Tako se u literaturi, od strane razlicitih autora, može naci nekoliko naziva za isti referentni sustav, okvir, datum. Potrebno je sto prije jednoznacno definirati nazive i kratice novih i starih sustava, datuma i okvira zbog sve vise korisnika prostornih podloga koji nisu geodetske struke. Prostorne podloge su danas temelj svih baza prostornih podataka koje služe za planiranje, projektiranje, analize u razlicitim državnim i javnim institucijama te privatnim tvrtkama. Također, važan je razlog za standardizaciju nacionalnih geodetskih referentnih koordinatnih sustava u Republici Hrvatskoj da cemo ulaskom u Europsku uniju morati koordinirati i razmjenjivati prostorne podatke s drugim državama clanicama. Sam proces ce biti puno jednostavniji sa sređenim, te u skladu s međunarodnim normama, usklađenim definicijama geodetskih referentnih sustava. Kljucne rijeci: ISO norma 19111, referentni

Ovaj rad bavi se ispitivanjem metoda transformacije katastarskih podataka, kao i izborom najbolje gustoce identicnih tocaka potrebnih za naknadni proces homogenizacije katastarskog plana nastalog grafickom metodom izmjere. Kao pilot podrucje odabrana je K.o. Brckovljani. Transformacija katastarskih podataka obavljena je koristenjem Jedinstvenog transformacijskog modela i 7–parametarske transformacije. Rezultati usporedbe dviju transformacija upucuju na Jedinstveni transformacijski model kao bolje rjesenje, buduci da za razliku od 7-parametarske transformacije izbjegava dodatne radove potrebne za određivanje lokalnih parametara te daje zadovoljavajucu tocnost. U postupku homogenizacije, glede gustoce, određena su tri uzorka identicnih tocaka uspoređujuci katastarski plan s digitalnim ortofoto planom mjerila 1:5000. Najveca postignuta gustoca od 0, 16 IT/ha, iako ekonomski najnepovoljnija, pokazala se kao jedina opravdana opcija u tehnickom smislu, buduci da su manje gustoce na kontrolnim tockama upucivale na degradaciju tocnosti katastarskog plana, sto ni u kom slucaju nije dopustivo.

Independent quality control of the national geoid model HRG2000 was performed using 65 control points, obtained through the realization of EUVN and EUVN_DA projects and the Croatian fundamental gravity network. Ellipsoidal heights and positions of the control points are precisely determined by GNSS measurements while the geodetic heights are obtained by geometric levelling.

Odlukom Vlade RH definiran je novi referentni koordinatni sustav kartografske projekcije (HTRS96/TM) koji bi do 2010. godine morao uci u službenu primjenu. Poveznica između starog i novog referentnog koordinatnog sustava ostvarena je pomocu novog Jedinstvenog transformacijskog modela. U Hrvatskoj je oko 25% katastarskih planova izrađeno pomocu numerickih metoda izmjere (polarna i ortogonalna) pri cemu je kao oslonac geodetske osnove koristena trigonometrijska mreža razvijena u starom položajnom referentnom koordinatnom sustavu (HDKS). Numericke izmjere su u najvecem opsegu provedene u razdoblju od pedesetih do sedamdesetih godina proslog stoljeca. Tocnost tih izmjera je prilagođena mjerilima katastarskog plana, ali se opcenito krece u intervalu od ±10 cm. Preliminarna analiza izmjere je provedena za katastarsku opcinu Topusko. Numericka izmjera katastarske opcine Topusko je provedena s ukupno 270 tocaka geodetske osnove. Izabrane tocke geodetske osnove (10 tocaka osnove + 3 trigonometra) su izražene u novom položajnom datumu (ETRS89) na dva razlicita nacina. Prvi nacin određivanja koordinata u HTRS96/TM sustavu proveden je transformacijom starih koordinata, izraženih u HDKS/GK, primjenom Jedinstvenog transformacijskog modela. Drugi nacin određivanja koordinata je proveden terenskom izmjerom pomocu visoko preciznog pozicijskog servisa (VPPS) CROPOS sustava. Rezultati su uspoređeni, te je napravljena ocjena primjenjivosti Jedinstvenog transformacijskog modela za ovakve potrebe.

In Republic of Croatia the Law on State Survey and Real Estate Cadastre regulates the maintenance of cadastre and its gradually adjustment to the real estate cadastre, Currently, is in progress the establishment of real estate cadastre by the new cadastral surveys for 5% of the Croatian territory. For the remaining areas establishment is planned by individual parcel translation. The most important and difficult precondition is cadastral plan geometric accuracy improvement (homogenization). Pursuant to Law Article 71 and Article 12 of the Ordinance on the cadastral survey and technical reambulation, geometric accuracy improvement is done by comparing orthophoto with cadastral plan thru identical points. This paper analyzes the number and selection of identical points, as well as compares three different computer programs which can perform local transformation. Quality of geometric accuracy improvement was observed thru several analyses.

The Fundamental Gravity Network (FGN) is foundation for all national gravity measurements. This network consists of 42 points: 6 absolute gravity points (0. Order Gravity Network) and 36 relative gravity points (I. Order Gravity Network). Further densification of FGN will be carried out by the lower order networks (II. Order Gravity Network). Fundamental gravity points should be homogeneously spaced over the whole state. In some large countries the distance between gravity points can be more than few hundred kilometres. Levelling connection of the absolute an first order gravity points at the national levelling network benchmarks was not performed. Also, the position of gravity points in respect to existing geodetic network stayed unknown. Quality positional and height definition of gravity points is necessary for calculating different corrections, which are needed for processing gravimetric measurements. By implementation of the FGN Finalization Project, along with already finalized projects, the modern gravity foundation for the Republic of Croatia will be established.

The paper depicts concise historical overview on gravity measurements on the territory of the Republic of Croatia, as well as on going activities in the field of fundamental gravity works and, in the last part, outlines planned activities in same field. Although first gravimetric measurements on the territory of the Republic of Croatia where relative measurements performed between 1887 and 1894 in the area of Rijeka city, first activities on establishment of the Fundamental Gravity Network were done just about 1950s by the VGI (Military Geographical Institute), when Croatia was part of former Yugoslavia. In course of mentioned works, the First Order Gravity Network of Yugoslavia was established with connection of central station (Belgrade) to absolute stations in Paris. Six of 15 first order stations where on the territory of Croatia. Subsequently, work on the second order network started, by finalization of which, the Fundamental Gravity Network of former Yugoslavia was established in late 1960s. Even though considerable part of the Fundamental Gravity Network of former Yugoslavia was on the territory of Croatia, after gaining independence, because of inability to gain data on the network that is kept in Belgrade and because of condition and layout of existing gravity stations, the Republic of Croatia had to start over with establishment of a fundamental gravity network. Hence, Croatia established 6 absolute gravity stations that form the Zero Order Gravity Network of the Republic of Croatia. Following, the First Order Gravity Network has been established that comprises 36 relative stations (including 25 stations from old fundamental network). Today, the Fundamental Gravity Network that comprises zero and first order network is completely established and there is an on going project of the Second Order Gravity Network. In addition, realization of the gravity meter calibration line, cyclic re-surveys of the Fundamental Gravity Network, as well as its densification on land area and extension on the Croatian islands are planned.

Mjerenje visina u geodeziji se kontinuirano provodi vec nekoliko stoljeca. Tijekom vremena doslo je do znacajnog razvoja instrumentarija i mjernih postupaka. Jedna specijalna i relativno zahtjevna zadaca je prijenos visina preko velikih voda. Utjecaji raznorodnih pogresaka, kao sto su simetricna i nesimetricna refrakcija, su posebice preko otvorenih vodenih povrsina nepredvidivi i u konacnom iznosu neizracunljivi. Uobicajena metoda, prebacivanja visina geometrijskim nivelmanom s milimetarskom preciznoscu se ovdje kao prihvatljivi mjerni postupak može u potpunosti iskljuciti. Vrlo brzo se nailazi na granicne mogucnosti buduci da udaljenosti od nivelira do nivelmanskih letava trebaju biti jednake. Osim toga, egzaktna ocitanja na nivelmanskim letvama na tako velikim udaljenostima nisu moguca. U okviru projekta prijenosa visina s kopna na otoke sjevernog Jadrana uspoređene su visine određene geometrijskim, trigonometrijskim i GNSS nivelmanom. U tu svrhu je koristen HRG2000 model geoida pomocu kojeg su elipsoidne visine transformirane u (normalne) ortometrijske. Tek nakon toga je bilo moguce usporediti relativne visinske razlike određene razlicitim metodama mjerenja i provesti analizu preciznosti ostvarenih rezultata. Temeljem provedenih analiza dobio se odgovor na pitanje da li je moguce ostvariti prijenos visina trigonometrijskim nivelmanom sa zahtijevanom subcentimetarskom preciznoscu, koristeci nova tehnoloska instrumentalna rjesenja. U tu svrhu poslužila je usporedba prijenosa visina s kopna na otok Rab gdje je 60-tih godina proslog stoljeca ostvaren prijenos visina geometrijskim nivelmanom pomocu specijalnog postupka.

Geodetsku osnovu za katastarske izmjere i inženjerske zadace manjih zahtjeva preciznosti, tradicionalno je do sada predstavljala mreža stabiliziranih tocaka na zemljinoj povrsini s koordinatama određenim u državnom koordinatnom sustavu. Uzmu li se u obzir suvremene tehnologije koje su u primjeni može se reci da takva mreža tocaka, s motrista sustava za globalno satelitsko pozicioniranje, pri određivanju položaja tocaka detalja, predstavlja pasivnu geodetsku osnovu. Nasuprot tome aktivna geodetska osnova s mrežom referentnih stanica s precizno određenim koordinatama u globalnom geocentricnom referentnom sustavu osigurava servis satelitskog pozicioniranja razlicitih razina preciznosti. Primjena satelitskog pozicioniranja s pasivne geodetske osnove moguca je uspostavom referentnog uređaja na jednoj ili vise tocaka primjenom kinematickog i statickog pozicioniranja. U cilju eksperimentalnog istraživanja preciznosti i efikasnosti razlicitih metoda pozicioniranja na kracim udaljenostima opažanjem umjetnih zemljinih satelita obavljena su testna mjerenja na kalibracijskoj bazi Geodetskog fakulteta u odnosu na samo jednu referentnu stanicu.

Realizacijom mreže referentnih stanica vec nekoliko godina u vecem broju država Europe posredstvom servisa za satelitsko pozicioniranje u potpunosti su podržane najcesce primjene u postprocessingu za raznovrsne geodetske zadace. Na osnovu uspostavljene mreže referentnih stanica, njene raspoloživosti i konceptu koji je stavlja na raspolaganje krajnjem korisniku svakom je korisniku zajamceno da ce pri odgovarajucem mjernom postupku moci prikupljati mjerenja kao infrastrukturnu uslugu od strane države i to primjerene kvalitete, koja osigurava obradu podataka mjerenja u postprocessingu do subcentimetarske razine preciznosti u položajnom i 1-3 cm u visinskom smislu. Mreže referentnih stanica su kvalitetna supstitucija dosadasnjim klasicnim mrežama stalnih geodetskih tocaka. Primjena satelitski podržanih postupaka dostigla je u međuvremenu novu kvalitetu. GPS se ne primjenjuje samo kao precizan, fleksibilan i ekonomican mjerni postupak, nego je prerastao u osnovu za određivanje stalnih tocaka geodetske osnove. Uvođenje satelitski podržanih postupaka u podrucju katastra nekretnina znacajno se reflektira na buducu strukturu klasicnih mreža stalnih tocaka geodetske osnove kao i na izgradnju koordinatnog katastra. Posebice, uspostava satelitskih sustava za poziciniranje smanjuje potrebu za trajno stabiliziranim tockama.