Nakon uspostave šest apsolutnih točaka nultog reda (1996.-2000.) te razvoja mreže prvog reda koja... more Nakon uspostave šest apsolutnih točaka nultog reda (1996.-2000.) te razvoja mreže prvog reda koja sadrži 36 točaka pravilno raspoređenih po cijelom teritoriju države (2003.), prišlo se poslovima vezanim uz daljnja progušćenja na način da se krenulo s uspostavom mreže drugog reda. Kao pilot područje na kojem će biti ispitane metode pri planiranju, odabiru i stabilizaciji novih točaka, načinima izmjere te primjerenosti postignutih rezultata, odabrano je područje Istre. Terenski radovi okončani su u travnju ove godine te su na točkama osim gravimetrijskih mjerenja obavljena GPS i nivelmanska mjerenja sa svrhom uključivanja gravimetrijskih točaka drugog reda u službeni položajni i visinski sustav. Mreža na području Istre sastoji se od ukupno 18 točaka od čega su tri točke iz gravimetrijske mreže prvog reda i služe za uklapanje mreže u službeni gravimetrijski sustav dok je 15 točaka novo stabilizirano te predstavljaju prve točke drugog reda uspostavljene u Republici Hrvatskoj. Postignuta standardna odstupanja nepoznanica nakon izjednačenja koja iznose do 0.04 μms-2 te ostali pokazatelji koji će biti dani u članku govore u prilog primjerenosti metoda korištenih pri uspostavi ove mreže te daju dobru podlogu za nastavak njenog razvoja u ostalim dijelovima Hrvatske. Slijedeće područje na kojem se planira razvoj gravimetrijske mreže drugog reda je područje istočne Slavonije i planirano je za ovu jesen. Ukoliko se uspije održati nametnuta dinamika poslovi bi mogli biti okončani kroz 6-7 godina čime bi Hrvatska dobila homogenu mrežu od oko 250 točaka na kojima su osim ubrzanja sile teže kvalitetno određeni i visina te položaj. Ova mreža dati će odgovor na mnoga praktična pitanja vezana uz fizikalnu geodeziju na nacionalnoj i regionalnoj razini, pomoći pri kontroli postojeće te razvoju novih visinskih mreža, izradi novih modela geoida...
By demand for densification of EUVN_DA network with additional points on state territory, Republi... more By demand for densification of EUVN_DA network with additional points on state territory, Republic Croatia is again activated in project EUVN_DA on national level in year 2005. During project EUVN_DA network is expanded from 8 existing points to 20 points. Difference between EGG97 and EUVN model showed possible errors on some areas or points (HR05 Split). Therefore, those errors were eliminated by measurements and results were free of errors from first EUVN campaign in year 1997. Differences between national model of geoid HRG2000 and EUVN show better adjustment of geoid surface for state area than continental EGG97 geoid. Therefore they are additional control in densification of EUVN_DA project. Result analysis along coast showed large differences between geoid models. From the old gravity network (84 gravity points) 25 gravity points were used. After stabilization of 11 new gravity points Basic Gravity Network comprises 36 gravity points. Finalization of establishment of the Fundamental Gravity Network of the Republic of Croatia is also planned to improve absolute national geoid orientation. As well, EUVN points in Croatia, based on Fundamental Gravity Network, will ensure better identification of geoid differences on continental level.
In the Croatian part of the Adriatic Sea, there are 698 islands, 389 islets and 78
reefs, which m... more 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.
Posljednjih godina u svijetu, a također i kod nas, inženjerska geodezija u graditeljstvu je suoče... more Posljednjih godina u svijetu, a također i kod nas, inženjerska geodezija u graditeljstvu je suočena sa sve složenijim mjerno tehničkim zahtjevima. Obzirom na prevladavajuću primjenu inženjerske geodezije u graditeljstvu može se utvrditi da je glavno područje primjene inženjerske geodezije upravo graditeljstvo. Sve ono što je u ne tako dalekoj prošlosti s aspekta geodetske znanosti sa svojim zahtjevima predstavljala niskogradnja, danas a posebice u budućnosti težište primjene inženjerske geodezije preseljavati će se sve više na visokogradnju s naglaskom na čelično betonske konstrukcijske elemente. Sukladno sve kompleksnijim zahtjevima koje pred sebe postavlja graditeljstvo inženjerska geodezija u graditeljstvu konfrontirana je sa sve većim zahtjevima preciznosti. Sustav i analiza mjerenja na branama, tunelima, mostovima, industrijskim postrojenjima, tornjevima, neboderima su posebno komplicirani i iziskuju često uspostavljanje mreža najveće preciznosti i s time u svezi efektivne mjerne metode i obradu podataka mjerenja.
Mjerenje visina u geodeziji se kontinuirano provodi već nekoliko stoljeća. Tijekom vremena došlo
... more Mjerenje visina u geodeziji se kontinuirano provodi već nekoliko stoljeća. Tijekom vremena došlo je do značajnog razvoja instrumentarija i mjernih postupaka. Jedna specijalna i relativno zahtjevna zadaća je prijenos visina preko velikih voda. Utjecaji raznorodnih pogrešaka, kao što su simetrična i nesimetrična refrakcija, su posebice preko otvorenih vodenih površina nepredvidivi i u konačnom iznosu neizračunljivi. Uobičajena metoda, prebacivanja visina geometrijskim nivelmanom s milimetarskom preciznošću se ovdje kao prihvatljivi mjerni postupak može u potpunosti isključiti. Vrlo brzo se nailazi na granične mogućnosti budući da udaljenosti od nivelira do nivelmanskih letava trebaju biti jednake. Osim toga, egzaktna očitanja na nivelmanskim letvama na tako velikim udaljenostima nisu moguća. U okviru projekta prijenosa visina s kopna na otoke sjevernog Jadrana uspoređene su visine određene geometrijskim, trigonometrijskim i GNSS nivelmanom. U tu svrhu je korišten HRG2000 model geoida pomoću kojeg su elipsoidne visine transformirane u (normalne) ortometrijske. Tek nakon toga je bilo moguće usporediti relativne visinske razlike određene različitim metodama mjerenja i provesti analizu preciznosti ostvarenih rezultata. Temeljem provedenih analiza dobio se odgovor na pitanje da li je moguće ostvariti prijenos visina trigonometrijskim nivelmanom sa zahtijevanom subcentimetarskom preciznošću, koristeći nova tehnološka instrumentalna rješenja. U tu svrhu poslužila je usporedba prijenosa visina s kopna na otok Rab gdje je 60- tih godina prošlog stoljeća ostvaren prijenos visina geometrijskim nivelmanom pomoću specijalnog postupka.
Težište primjene inženjerske geodezije preseljava se sve više s niskogradnje na visokogradnju s
n... more Težište primjene inženjerske geodezije preseljava se sve više s niskogradnje na visokogradnju s naglaskom na sve kompleksnijim projektnim zadaćama koje pred sebe postavlja graditeljstvo. Inženjerska geodezija u graditeljstvu konfrontirana je sa sve većim zahtjevima pri čemu se geodetski mjerni postupci primjenjuju sve učestalije za potrebe ispitivanja geometrijskog oblika građevina ili njihovog praćenja tijekom i nakon građenja. Najčešće se pri tome u različitim vremenskim epohama uspoređuju koordinate karakterističnih reprezentativnih točaka objekta, odnosno područja koji je predmet promatranja. U tu svrhu prikladni su elektronski tahimetri, posebno automatizirane verzije s integriranim računalom i automatskim prepoznavanjem prizme odnosno njenim automatskim praćenjem. Kombiniraju li se geodetski senzori u apsolutnom referentnom sustavu s daljnjim senzorima na objektu koji je predmet mjerenja u hibridni mjerni sustav te realizira li se funkcija dojavljivanja u slučaju graničnih uvjeta ostvaren je sustav kontinuiranog praćenja. Posebno osjetljiva i vrlo važna zadaća pri tome je pouzdano prezentiranje rezultata mjerenja te njihovo stavljanje na raspolaganje u realnom vremenu kako bi se prevenirale negativne posljedice koje su rezultat slijeganja, pomaka ili u krajnjoj konzekvenci deformacija objekta.
The Fundamental Gravity Network (FGN) is foundation for all national gravity measurements.
This n... more 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. Like the other geodetic networks in the Republic of Croatia, gravity network also followed the trend of connecting at the European level. The result of this trend was UNIGRACE project. Six absolute gravity points have been established (0. Order Gravity Network) during two phases of UNIGRACE project. These points provided reference for all other gravity works in Croatia. After the finalization of UNIGRACE project the main preconditions for gravity network of the first order, which leans on established six absolute stations, were accomplished. In the year 2000 revision of inherited gravity network of the first order was started. The revision showed that 25 old points could be used for the new, I. order, gravity network. Also, 11 new I. order gravity points were stabilized. With the 11 new I. order gravity points the frame for the Fundamental Gravity Network has been founded, that comprises 36 points. The gravity measurements have been performed during year 2003. After processing and measurement adjustment, the gravity value at each point has been obtained. Levelling connection of the absolute and 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.
Independent quality control of the national geoid model HRG2000 was performed using 65 control po... more 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. The latest geoid model HRG2000 is related to the old vertical system. The analysis indicated the need for a new improved national geoid model which has to be connected to the new vertical system HVRS71. As preparation, and as first step, an analysis of the global geopotential models was made, using eleven recent CHAMP and/or GRACE global models. The statistics of the differences between GNSS/levelling height anomalies (ζHVRS71) and corresponding anomalies obtained from global geopotential models (ζMODEL) shows that EGM2008 model is most suitable at this moment. Another interesting fact is that all global models are approximately 93 cm above the new Croatian vertical datum.
In September and November 2007
Croatian Fundamental gravity network (FGN) has
been extended to no... more In September and November 2007 Croatian Fundamental gravity network (FGN) has been extended to north Adriatic islands by relative gravimetry. The paper describes FGN extension measurements, applied adjustment models and analyses of results with critical remarks. In order to ensure homogeneity of the network, the extension has been designed in accordance with initial FGN, apart from station separation and mean of transportation. The extension has been adjusted according to the least squares principle, first as independent free network, subsequently as biased network with stations from present FGN fixed. Two adjustment models have been applied for both datum definitions. For one model of adjustment daily drift corrections have been determined prior to adjustment, while in second introduced as parameters in functional model. For both models of adjustment, stochastic model is based on variances of gravity readings but involves total mathematical correlation and estimated uncertainty of daily drift corrections (if determined prior to adjustment). Although drift values differs significantly, estimated gravity values from two models show no significant difference (up to 0.008 μms-2). Standard deviations of estimated gravity values for model 1 and 2 do not exceed 0.08 μms-2 and 0.09 μms-2, respectively. All computations have been preformed automatically by several programming functions developed in Matlab. Since within next 2 years FGN extension to all significant Adriatic islands is planned, described extension procedure is only a first phase that shall provide valuable experience in forthcoming projects.
The EUVN points are represent one basic element of the European geodetic infrastructure. They
ser... more The EUVN points are represent one basic element of the European geodetic infrastructure. They serve as a control of the existing continental and national geoid solutions and for the estimation of height datum differences. After the first analysis, discrepancies between gravimetric geoid EGG97 and the point-wise EUVN geoid were detected due to errors in one of compared models. Croatian Geodetic Institute (CGI) received all materials related to EUVN project from the State Geodetic Administration. Analyse of the received materials shows that some height data, which have been sent to the EUREFUELN data centre, were calculated using benchmarks whose heights are in different height datum. This paper represents discrepancies between EGG97 and EUVN after using uniform new official height datum in Croatia – HVRS71 and densification project EUVN_DA on the territory of the Republic of Croatia.
Crta srednjih viših visokih voda (SVVV) određuje granicu unutar pomorskog dobra između
morske oba... more Crta srednjih viših visokih voda (SVVV) određuje granicu unutar pomorskog dobra između morske obale i ostalog dijela pomorskog dobra. Razradom pravne regulative vezane uz pomorsko dobro javlja se potreba da se crta SVVV kvalitetno i jednostavno odredi. Pošto je crta SVVV usko vezana uz mareografska mjerenja, za shvaćanje njene definicije potrebno se upoznati s rezultatima tih mjerenja. Praktično određivanje crte SVVV svodi se na prijenos visina različitim nivelmanskim metodama pri čemu je neophodno korištenje točaka visinskog sustava. Pošto se trenutno nalazimo u prelaznom razdoblju u kojem je potrebno dosadašnju upotrebu povijesnog referentnog visinskog sustava zamijeniti novim referentnim visinskim sustavom, više pažnje bit će posvećeno tome što nam te promjene donose.
Nakon uspostave šest apsolutnih točaka nultog reda (1996.-2000.) te razvoja mreže prvog reda koja... more Nakon uspostave šest apsolutnih točaka nultog reda (1996.-2000.) te razvoja mreže prvog reda koja sadrži 36 točaka pravilno raspoređenih po cijelom teritoriju države (2003.), prišlo se poslovima vezanim uz daljnja progušćenja na način da se krenulo s uspostavom mreže drugog reda. Kao pilot područje na kojem će biti ispitane metode pri planiranju, odabiru i stabilizaciji novih točaka, načinima izmjere te primjerenosti postignutih rezultata, odabrano je područje Istre. Terenski radovi okončani su u travnju ove godine te su na točkama osim gravimetrijskih mjerenja obavljena GPS i nivelmanska mjerenja sa svrhom uključivanja gravimetrijskih točaka drugog reda u službeni položajni i visinski sustav. Mreža na području Istre sastoji se od ukupno 18 točaka od čega su tri točke iz gravimetrijske mreže prvog reda i služe za uklapanje mreže u službeni gravimetrijski sustav dok je 15 točaka novo stabilizirano te predstavljaju prve točke drugog reda uspostavljene u Republici Hrvatskoj. Postignuta standardna odstupanja nepoznanica nakon izjednačenja koja iznose do 0.04 μms-2 te ostali pokazatelji koji će biti dani u članku govore u prilog primjerenosti metoda korištenih pri uspostavi ove mreže te daju dobru podlogu za nastavak njenog razvoja u ostalim dijelovima Hrvatske. Slijedeće područje na kojem se planira razvoj gravimetrijske mreže drugog reda je područje istočne Slavonije i planirano je za ovu jesen. Ukoliko se uspije održati nametnuta dinamika poslovi bi mogli biti okončani kroz 6-7 godina čime bi Hrvatska dobila homogenu mrežu od oko 250 točaka na kojima su osim ubrzanja sile teže kvalitetno određeni i visina te položaj. Ova mreža dati će odgovor na mnoga praktična pitanja vezana uz fizikalnu geodeziju na nacionalnoj i regionalnoj razini, pomoći pri kontroli postojeće te razvoju novih visinskih mreža, izradi novih modela geoida...
By demand for densification of EUVN_DA network with additional points on state territory, Republi... more By demand for densification of EUVN_DA network with additional points on state territory, Republic Croatia is again activated in project EUVN_DA on national level in year 2005. During project EUVN_DA network is expanded from 8 existing points to 20 points. Difference between EGG97 and EUVN model showed possible errors on some areas or points (HR05 Split). Therefore, those errors were eliminated by measurements and results were free of errors from first EUVN campaign in year 1997. Differences between national model of geoid HRG2000 and EUVN show better adjustment of geoid surface for state area than continental EGG97 geoid. Therefore they are additional control in densification of EUVN_DA project. Result analysis along coast showed large differences between geoid models. From the old gravity network (84 gravity points) 25 gravity points were used. After stabilization of 11 new gravity points Basic Gravity Network comprises 36 gravity points. Finalization of establishment of the Fundamental Gravity Network of the Republic of Croatia is also planned to improve absolute national geoid orientation. As well, EUVN points in Croatia, based on Fundamental Gravity Network, will ensure better identification of geoid differences on continental level.
In the Croatian part of the Adriatic Sea, there are 698 islands, 389 islets and 78
reefs, which m... more 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.
Posljednjih godina u svijetu, a također i kod nas, inženjerska geodezija u graditeljstvu je suoče... more Posljednjih godina u svijetu, a također i kod nas, inženjerska geodezija u graditeljstvu je suočena sa sve složenijim mjerno tehničkim zahtjevima. Obzirom na prevladavajuću primjenu inženjerske geodezije u graditeljstvu može se utvrditi da je glavno područje primjene inženjerske geodezije upravo graditeljstvo. Sve ono što je u ne tako dalekoj prošlosti s aspekta geodetske znanosti sa svojim zahtjevima predstavljala niskogradnja, danas a posebice u budućnosti težište primjene inženjerske geodezije preseljavati će se sve više na visokogradnju s naglaskom na čelično betonske konstrukcijske elemente. Sukladno sve kompleksnijim zahtjevima koje pred sebe postavlja graditeljstvo inženjerska geodezija u graditeljstvu konfrontirana je sa sve većim zahtjevima preciznosti. Sustav i analiza mjerenja na branama, tunelima, mostovima, industrijskim postrojenjima, tornjevima, neboderima su posebno komplicirani i iziskuju često uspostavljanje mreža najveće preciznosti i s time u svezi efektivne mjerne metode i obradu podataka mjerenja.
Mjerenje visina u geodeziji se kontinuirano provodi već nekoliko stoljeća. Tijekom vremena došlo
... more Mjerenje visina u geodeziji se kontinuirano provodi već nekoliko stoljeća. Tijekom vremena došlo je do značajnog razvoja instrumentarija i mjernih postupaka. Jedna specijalna i relativno zahtjevna zadaća je prijenos visina preko velikih voda. Utjecaji raznorodnih pogrešaka, kao što su simetrična i nesimetrična refrakcija, su posebice preko otvorenih vodenih površina nepredvidivi i u konačnom iznosu neizračunljivi. Uobičajena metoda, prebacivanja visina geometrijskim nivelmanom s milimetarskom preciznošću se ovdje kao prihvatljivi mjerni postupak može u potpunosti isključiti. Vrlo brzo se nailazi na granične mogućnosti budući da udaljenosti od nivelira do nivelmanskih letava trebaju biti jednake. Osim toga, egzaktna očitanja na nivelmanskim letvama na tako velikim udaljenostima nisu moguća. U okviru projekta prijenosa visina s kopna na otoke sjevernog Jadrana uspoređene su visine određene geometrijskim, trigonometrijskim i GNSS nivelmanom. U tu svrhu je korišten HRG2000 model geoida pomoću kojeg su elipsoidne visine transformirane u (normalne) ortometrijske. Tek nakon toga je bilo moguće usporediti relativne visinske razlike određene različitim metodama mjerenja i provesti analizu preciznosti ostvarenih rezultata. Temeljem provedenih analiza dobio se odgovor na pitanje da li je moguće ostvariti prijenos visina trigonometrijskim nivelmanom sa zahtijevanom subcentimetarskom preciznošću, koristeći nova tehnološka instrumentalna rješenja. U tu svrhu poslužila je usporedba prijenosa visina s kopna na otok Rab gdje je 60- tih godina prošlog stoljeća ostvaren prijenos visina geometrijskim nivelmanom pomoću specijalnog postupka.
Težište primjene inženjerske geodezije preseljava se sve više s niskogradnje na visokogradnju s
n... more Težište primjene inženjerske geodezije preseljava se sve više s niskogradnje na visokogradnju s naglaskom na sve kompleksnijim projektnim zadaćama koje pred sebe postavlja graditeljstvo. Inženjerska geodezija u graditeljstvu konfrontirana je sa sve većim zahtjevima pri čemu se geodetski mjerni postupci primjenjuju sve učestalije za potrebe ispitivanja geometrijskog oblika građevina ili njihovog praćenja tijekom i nakon građenja. Najčešće se pri tome u različitim vremenskim epohama uspoređuju koordinate karakterističnih reprezentativnih točaka objekta, odnosno područja koji je predmet promatranja. U tu svrhu prikladni su elektronski tahimetri, posebno automatizirane verzije s integriranim računalom i automatskim prepoznavanjem prizme odnosno njenim automatskim praćenjem. Kombiniraju li se geodetski senzori u apsolutnom referentnom sustavu s daljnjim senzorima na objektu koji je predmet mjerenja u hibridni mjerni sustav te realizira li se funkcija dojavljivanja u slučaju graničnih uvjeta ostvaren je sustav kontinuiranog praćenja. Posebno osjetljiva i vrlo važna zadaća pri tome je pouzdano prezentiranje rezultata mjerenja te njihovo stavljanje na raspolaganje u realnom vremenu kako bi se prevenirale negativne posljedice koje su rezultat slijeganja, pomaka ili u krajnjoj konzekvenci deformacija objekta.
The Fundamental Gravity Network (FGN) is foundation for all national gravity measurements.
This n... more 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. Like the other geodetic networks in the Republic of Croatia, gravity network also followed the trend of connecting at the European level. The result of this trend was UNIGRACE project. Six absolute gravity points have been established (0. Order Gravity Network) during two phases of UNIGRACE project. These points provided reference for all other gravity works in Croatia. After the finalization of UNIGRACE project the main preconditions for gravity network of the first order, which leans on established six absolute stations, were accomplished. In the year 2000 revision of inherited gravity network of the first order was started. The revision showed that 25 old points could be used for the new, I. order, gravity network. Also, 11 new I. order gravity points were stabilized. With the 11 new I. order gravity points the frame for the Fundamental Gravity Network has been founded, that comprises 36 points. The gravity measurements have been performed during year 2003. After processing and measurement adjustment, the gravity value at each point has been obtained. Levelling connection of the absolute and 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.
Independent quality control of the national geoid model HRG2000 was performed using 65 control po... more 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. The latest geoid model HRG2000 is related to the old vertical system. The analysis indicated the need for a new improved national geoid model which has to be connected to the new vertical system HVRS71. As preparation, and as first step, an analysis of the global geopotential models was made, using eleven recent CHAMP and/or GRACE global models. The statistics of the differences between GNSS/levelling height anomalies (ζHVRS71) and corresponding anomalies obtained from global geopotential models (ζMODEL) shows that EGM2008 model is most suitable at this moment. Another interesting fact is that all global models are approximately 93 cm above the new Croatian vertical datum.
In September and November 2007
Croatian Fundamental gravity network (FGN) has
been extended to no... more In September and November 2007 Croatian Fundamental gravity network (FGN) has been extended to north Adriatic islands by relative gravimetry. The paper describes FGN extension measurements, applied adjustment models and analyses of results with critical remarks. In order to ensure homogeneity of the network, the extension has been designed in accordance with initial FGN, apart from station separation and mean of transportation. The extension has been adjusted according to the least squares principle, first as independent free network, subsequently as biased network with stations from present FGN fixed. Two adjustment models have been applied for both datum definitions. For one model of adjustment daily drift corrections have been determined prior to adjustment, while in second introduced as parameters in functional model. For both models of adjustment, stochastic model is based on variances of gravity readings but involves total mathematical correlation and estimated uncertainty of daily drift corrections (if determined prior to adjustment). Although drift values differs significantly, estimated gravity values from two models show no significant difference (up to 0.008 μms-2). Standard deviations of estimated gravity values for model 1 and 2 do not exceed 0.08 μms-2 and 0.09 μms-2, respectively. All computations have been preformed automatically by several programming functions developed in Matlab. Since within next 2 years FGN extension to all significant Adriatic islands is planned, described extension procedure is only a first phase that shall provide valuable experience in forthcoming projects.
The EUVN points are represent one basic element of the European geodetic infrastructure. They
ser... more The EUVN points are represent one basic element of the European geodetic infrastructure. They serve as a control of the existing continental and national geoid solutions and for the estimation of height datum differences. After the first analysis, discrepancies between gravimetric geoid EGG97 and the point-wise EUVN geoid were detected due to errors in one of compared models. Croatian Geodetic Institute (CGI) received all materials related to EUVN project from the State Geodetic Administration. Analyse of the received materials shows that some height data, which have been sent to the EUREFUELN data centre, were calculated using benchmarks whose heights are in different height datum. This paper represents discrepancies between EGG97 and EUVN after using uniform new official height datum in Croatia – HVRS71 and densification project EUVN_DA on the territory of the Republic of Croatia.
Crta srednjih viših visokih voda (SVVV) određuje granicu unutar pomorskog dobra između
morske oba... more Crta srednjih viših visokih voda (SVVV) određuje granicu unutar pomorskog dobra između morske obale i ostalog dijela pomorskog dobra. Razradom pravne regulative vezane uz pomorsko dobro javlja se potreba da se crta SVVV kvalitetno i jednostavno odredi. Pošto je crta SVVV usko vezana uz mareografska mjerenja, za shvaćanje njene definicije potrebno se upoznati s rezultatima tih mjerenja. Praktično određivanje crte SVVV svodi se na prijenos visina različitim nivelmanskim metodama pri čemu je neophodno korištenje točaka visinskog sustava. Pošto se trenutno nalazimo u prelaznom razdoblju u kojem je potrebno dosadašnju upotrebu povijesnog referentnog visinskog sustava zamijeniti novim referentnim visinskim sustavom, više pažnje bit će posvećeno tome što nam te promjene donose.
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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.
je do značajnog razvoja instrumentarija i mjernih postupaka. Jedna specijalna i relativno zahtjevna zadaća
je prijenos visina preko velikih voda. Utjecaji raznorodnih pogrešaka, kao što su simetrična i nesimetrična
refrakcija, su posebice preko otvorenih vodenih površina nepredvidivi i u konačnom iznosu neizračunljivi.
Uobičajena metoda, prebacivanja visina geometrijskim nivelmanom s milimetarskom preciznošću se ovdje
kao prihvatljivi mjerni postupak može u potpunosti isključiti. Vrlo brzo se nailazi na granične mogućnosti
budući da udaljenosti od nivelira do nivelmanskih letava trebaju biti jednake. Osim toga, egzaktna očitanja
na nivelmanskim letvama na tako velikim udaljenostima nisu moguća. U okviru projekta prijenosa visina s
kopna na otoke sjevernog Jadrana uspoređene su visine određene geometrijskim, trigonometrijskim i GNSS
nivelmanom. U tu svrhu je korišten HRG2000 model geoida pomoću kojeg su elipsoidne visine
transformirane u (normalne) ortometrijske. Tek nakon toga je bilo moguće usporediti relativne visinske
razlike određene različitim metodama mjerenja i provesti analizu preciznosti ostvarenih rezultata.
Temeljem provedenih analiza dobio se odgovor na pitanje da li je moguće ostvariti prijenos visina
trigonometrijskim nivelmanom sa zahtijevanom subcentimetarskom preciznošću, koristeći nova tehnološka
instrumentalna rješenja. U tu svrhu poslužila je usporedba prijenosa visina s kopna na otok Rab gdje je 60-
tih godina prošlog stoljeća ostvaren prijenos visina geometrijskim nivelmanom pomoću specijalnog
postupka.
naglaskom na sve kompleksnijim projektnim zadaćama koje pred sebe postavlja graditeljstvo. Inženjerska
geodezija u graditeljstvu konfrontirana je sa sve većim zahtjevima pri čemu se geodetski mjerni postupci
primjenjuju sve učestalije za potrebe ispitivanja geometrijskog oblika građevina ili njihovog praćenja
tijekom i nakon građenja. Najčešće se pri tome u različitim vremenskim epohama uspoređuju koordinate
karakterističnih reprezentativnih točaka objekta, odnosno područja koji je predmet promatranja. U tu svrhu
prikladni su elektronski tahimetri, posebno automatizirane verzije s integriranim računalom i automatskim
prepoznavanjem prizme odnosno njenim automatskim praćenjem. Kombiniraju li se geodetski senzori u
apsolutnom referentnom sustavu s daljnjim senzorima na objektu koji je predmet mjerenja u hibridni mjerni
sustav te realizira li se funkcija dojavljivanja u slučaju graničnih uvjeta ostvaren je sustav kontinuiranog
praćenja. Posebno osjetljiva i vrlo važna zadaća pri tome je pouzdano prezentiranje rezultata mjerenja te
njihovo stavljanje na raspolaganje u realnom vremenu kako bi se prevenirale negativne posljedice koje su
rezultat slijeganja, pomaka ili u krajnjoj konzekvenci deformacija objekta.
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. Like the other geodetic networks in the Republic
of Croatia, gravity network also followed the trend of connecting at the European level. The result
of this trend was UNIGRACE project. Six absolute gravity points have been established (0. Order
Gravity Network) during two phases of UNIGRACE project. These points provided reference for
all other gravity works in Croatia. After the finalization of UNIGRACE project the main
preconditions for gravity network of the first order, which leans on established six absolute
stations, were accomplished. In the year 2000 revision of inherited gravity network of the first
order was started. The revision showed that 25 old points could be used for the new, I. order,
gravity network. Also, 11 new I. order gravity points were stabilized. With the 11 new I. order
gravity points the frame for the Fundamental Gravity Network has been founded, that comprises 36
points. The gravity measurements have been performed during year 2003. After processing and
measurement adjustment, the gravity value at each point has been obtained. Levelling connection
of the absolute and 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 latest geoid model HRG2000 is related to the old vertical system. The analysis indicated the need for a new improved national geoid model which has to be connected to the new vertical system HVRS71. As preparation, and as first step, an analysis of the global geopotential models was made, using eleven recent CHAMP and/or GRACE global models. The statistics of the differences between GNSS/levelling height anomalies (ζHVRS71) and corresponding anomalies obtained from global geopotential models (ζMODEL) shows that EGM2008 model is most suitable at this moment. Another interesting fact is that all global models are approximately 93 cm above the new Croatian vertical datum.
Croatian Fundamental gravity network (FGN) has
been extended to north Adriatic islands by relative
gravimetry. The paper describes FGN extension
measurements, applied adjustment models and
analyses of results with critical remarks.
In order to ensure homogeneity of the network,
the extension has been designed in accordance with
initial FGN, apart from station separation and mean
of transportation.
The extension has been adjusted according to the
least squares principle, first as independent free
network, subsequently as biased network with
stations from present FGN fixed. Two adjustment
models have been applied for both datum
definitions. For one model of adjustment daily drift
corrections have been determined prior to
adjustment, while in second introduced as
parameters in functional model. For both models of
adjustment, stochastic model is based on variances
of gravity readings but involves total mathematical
correlation and estimated uncertainty of daily drift
corrections (if determined prior to adjustment).
Although drift values differs significantly,
estimated gravity values from two models show no
significant difference (up to 0.008 μms-2). Standard
deviations of estimated gravity values for model 1
and 2 do not exceed 0.08 μms-2 and 0.09 μms-2,
respectively.
All computations have been preformed
automatically by several programming functions
developed in Matlab.
Since within next 2 years FGN extension to all
significant Adriatic islands is planned, described
extension procedure is only a first phase that shall
provide valuable experience in forthcoming
projects.
serve as a control of the existing continental and national geoid solutions and for the estimation of height
datum differences. After the first analysis, discrepancies between gravimetric geoid EGG97 and the
point-wise EUVN geoid were detected due to errors in one of compared models. Croatian Geodetic
Institute (CGI) received all materials related to EUVN project from the State Geodetic Administration.
Analyse of the received materials shows that some height data, which have been sent to the EUREFUELN
data centre, were calculated using benchmarks whose heights are in different height datum. This
paper represents discrepancies between EGG97 and EUVN after using uniform new official height datum
in Croatia – HVRS71 and densification project EUVN_DA on the territory of the Republic of Croatia.
morske obale i ostalog dijela pomorskog dobra. Razradom pravne regulative vezane uz pomorsko dobro
javlja se potreba da se crta SVVV kvalitetno i jednostavno odredi. Pošto je crta SVVV usko vezana uz
mareografska mjerenja, za shvaćanje njene definicije potrebno se upoznati s rezultatima tih mjerenja.
Praktično određivanje crte SVVV svodi se na prijenos visina različitim nivelmanskim metodama pri čemu
je neophodno korištenje točaka visinskog sustava. Pošto se trenutno nalazimo u prelaznom razdoblju u
kojem je potrebno dosadašnju upotrebu povijesnog referentnog visinskog sustava zamijeniti novim
referentnim visinskim sustavom, više pažnje bit će posvećeno tome što nam te promjene donose.
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.
je do značajnog razvoja instrumentarija i mjernih postupaka. Jedna specijalna i relativno zahtjevna zadaća
je prijenos visina preko velikih voda. Utjecaji raznorodnih pogrešaka, kao što su simetrična i nesimetrična
refrakcija, su posebice preko otvorenih vodenih površina nepredvidivi i u konačnom iznosu neizračunljivi.
Uobičajena metoda, prebacivanja visina geometrijskim nivelmanom s milimetarskom preciznošću se ovdje
kao prihvatljivi mjerni postupak može u potpunosti isključiti. Vrlo brzo se nailazi na granične mogućnosti
budući da udaljenosti od nivelira do nivelmanskih letava trebaju biti jednake. Osim toga, egzaktna očitanja
na nivelmanskim letvama na tako velikim udaljenostima nisu moguća. U okviru projekta prijenosa visina s
kopna na otoke sjevernog Jadrana uspoređene su visine određene geometrijskim, trigonometrijskim i GNSS
nivelmanom. U tu svrhu je korišten HRG2000 model geoida pomoću kojeg su elipsoidne visine
transformirane u (normalne) ortometrijske. Tek nakon toga je bilo moguće usporediti relativne visinske
razlike određene različitim metodama mjerenja i provesti analizu preciznosti ostvarenih rezultata.
Temeljem provedenih analiza dobio se odgovor na pitanje da li je moguće ostvariti prijenos visina
trigonometrijskim nivelmanom sa zahtijevanom subcentimetarskom preciznošću, koristeći nova tehnološka
instrumentalna rješenja. U tu svrhu poslužila je usporedba prijenosa visina s kopna na otok Rab gdje je 60-
tih godina prošlog stoljeća ostvaren prijenos visina geometrijskim nivelmanom pomoću specijalnog
postupka.
naglaskom na sve kompleksnijim projektnim zadaćama koje pred sebe postavlja graditeljstvo. Inženjerska
geodezija u graditeljstvu konfrontirana je sa sve većim zahtjevima pri čemu se geodetski mjerni postupci
primjenjuju sve učestalije za potrebe ispitivanja geometrijskog oblika građevina ili njihovog praćenja
tijekom i nakon građenja. Najčešće se pri tome u različitim vremenskim epohama uspoređuju koordinate
karakterističnih reprezentativnih točaka objekta, odnosno područja koji je predmet promatranja. U tu svrhu
prikladni su elektronski tahimetri, posebno automatizirane verzije s integriranim računalom i automatskim
prepoznavanjem prizme odnosno njenim automatskim praćenjem. Kombiniraju li se geodetski senzori u
apsolutnom referentnom sustavu s daljnjim senzorima na objektu koji je predmet mjerenja u hibridni mjerni
sustav te realizira li se funkcija dojavljivanja u slučaju graničnih uvjeta ostvaren je sustav kontinuiranog
praćenja. Posebno osjetljiva i vrlo važna zadaća pri tome je pouzdano prezentiranje rezultata mjerenja te
njihovo stavljanje na raspolaganje u realnom vremenu kako bi se prevenirale negativne posljedice koje su
rezultat slijeganja, pomaka ili u krajnjoj konzekvenci deformacija objekta.
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. Like the other geodetic networks in the Republic
of Croatia, gravity network also followed the trend of connecting at the European level. The result
of this trend was UNIGRACE project. Six absolute gravity points have been established (0. Order
Gravity Network) during two phases of UNIGRACE project. These points provided reference for
all other gravity works in Croatia. After the finalization of UNIGRACE project the main
preconditions for gravity network of the first order, which leans on established six absolute
stations, were accomplished. In the year 2000 revision of inherited gravity network of the first
order was started. The revision showed that 25 old points could be used for the new, I. order,
gravity network. Also, 11 new I. order gravity points were stabilized. With the 11 new I. order
gravity points the frame for the Fundamental Gravity Network has been founded, that comprises 36
points. The gravity measurements have been performed during year 2003. After processing and
measurement adjustment, the gravity value at each point has been obtained. Levelling connection
of the absolute and 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 latest geoid model HRG2000 is related to the old vertical system. The analysis indicated the need for a new improved national geoid model which has to be connected to the new vertical system HVRS71. As preparation, and as first step, an analysis of the global geopotential models was made, using eleven recent CHAMP and/or GRACE global models. The statistics of the differences between GNSS/levelling height anomalies (ζHVRS71) and corresponding anomalies obtained from global geopotential models (ζMODEL) shows that EGM2008 model is most suitable at this moment. Another interesting fact is that all global models are approximately 93 cm above the new Croatian vertical datum.
Croatian Fundamental gravity network (FGN) has
been extended to north Adriatic islands by relative
gravimetry. The paper describes FGN extension
measurements, applied adjustment models and
analyses of results with critical remarks.
In order to ensure homogeneity of the network,
the extension has been designed in accordance with
initial FGN, apart from station separation and mean
of transportation.
The extension has been adjusted according to the
least squares principle, first as independent free
network, subsequently as biased network with
stations from present FGN fixed. Two adjustment
models have been applied for both datum
definitions. For one model of adjustment daily drift
corrections have been determined prior to
adjustment, while in second introduced as
parameters in functional model. For both models of
adjustment, stochastic model is based on variances
of gravity readings but involves total mathematical
correlation and estimated uncertainty of daily drift
corrections (if determined prior to adjustment).
Although drift values differs significantly,
estimated gravity values from two models show no
significant difference (up to 0.008 μms-2). Standard
deviations of estimated gravity values for model 1
and 2 do not exceed 0.08 μms-2 and 0.09 μms-2,
respectively.
All computations have been preformed
automatically by several programming functions
developed in Matlab.
Since within next 2 years FGN extension to all
significant Adriatic islands is planned, described
extension procedure is only a first phase that shall
provide valuable experience in forthcoming
projects.
serve as a control of the existing continental and national geoid solutions and for the estimation of height
datum differences. After the first analysis, discrepancies between gravimetric geoid EGG97 and the
point-wise EUVN geoid were detected due to errors in one of compared models. Croatian Geodetic
Institute (CGI) received all materials related to EUVN project from the State Geodetic Administration.
Analyse of the received materials shows that some height data, which have been sent to the EUREFUELN
data centre, were calculated using benchmarks whose heights are in different height datum. This
paper represents discrepancies between EGG97 and EUVN after using uniform new official height datum
in Croatia – HVRS71 and densification project EUVN_DA on the territory of the Republic of Croatia.
morske obale i ostalog dijela pomorskog dobra. Razradom pravne regulative vezane uz pomorsko dobro
javlja se potreba da se crta SVVV kvalitetno i jednostavno odredi. Pošto je crta SVVV usko vezana uz
mareografska mjerenja, za shvaćanje njene definicije potrebno se upoznati s rezultatima tih mjerenja.
Praktično određivanje crte SVVV svodi se na prijenos visina različitim nivelmanskim metodama pri čemu
je neophodno korištenje točaka visinskog sustava. Pošto se trenutno nalazimo u prelaznom razdoblju u
kojem je potrebno dosadašnju upotrebu povijesnog referentnog visinskog sustava zamijeniti novim
referentnim visinskim sustavom, više pažnje bit će posvećeno tome što nam te promjene donose.