Widespread use of GPS / GNSS technology sets the task of determining the normal (orthometric) heights of points. We know that it is necessary to determine the initial level surface – the surface of the geoid / quasigeoid. Determination of the quasigeoid surface can be performed by: 1) a gravimetric readout in the relevant region and building the regional geoid / quasigeoid; 2) a model of potential of gravitational field of the Earth; 3) an interpolation of quasigeoid’s heights on a surface given by leveling reference points, on which GNSS-leveling is carried. Most often the quasigeoid surface іs determined with a global gravity a model, for example EGM08, the standard deviation of this quasigeoid from the adopted system of heights, depending on the region, is from 3.5 to 25 cm. In the previous studies authors of the article show that the determination of the relative heights from processing of GNSS-observations is performed with the mean square error of about 5 mm at a distance of 3 km. The goal of the article is the calculation of the possible accuracy of determination of heights of the basic geodetic network points of the reference polygon both from geometric leveling with the Program of II class and from GNSS-definitions. The task of the practical metrology is in providing the compliance of the units of measurement of the device to the reference ones and in using the methods or methodologies of measuring performance that retain this unit of measurement. In case of using indirect measurements, which are satellite observations, it is necessary to provide the preservation of the standard unit of measurements during the measurements themselves, while processing the array of observations and during obtaining the resulting value. Then you can compare the distance or elevations between points, measured by ground-based methods and by processing satellite observations. It also necessary to consider that the terrestrial methods and satellite technologies of measurements are not equally influenced by the Earth’s gravity and the atmosphere. The accuracy of determination of points heights with the use of GNSS technology is influenced by several key factors, but the size of the errors mostly depends on the duration of observations. Therefore we will explore the change of the error of height determination caused by the change of the observation session duration. The accuracy of GNSS-leveling attestation as a method is influenced by such errors: definition of geodetic point’s height with processing of GNSS-observations; determination of the point’s height by geometric leveling; restoration of the reference surface of the sea level to determine the quasigeoid heights. To analyze the value of the error of point’s height determination using GNSS technology, daily observations of three GNSS-vectors, whose length were respectively – 10, 14 and 20 km, were performed. Geodetic coordinates of points were determined by sessions of GNSS-observations, the duration of which was increased gradually by 1 hour. For accurate values of points heights have been taken those, which were determined by the daily sessions of observations. The errors in determining the heights of points during a day describe sinusoids, moreover, with up to 6 hours of the session of observations the oscillation amplitude can reach 30 mm, for sessions lasting up to 16 hours – 5–10 mm and for sessions lasting more than 19 hours – about 1 mm. Therefore, to recieve accurate definitions of geodetic points’ heights and, accordingly, heights of quasigeoid using GNSS-leveling, the observation session should last from 19 to 24 hours. Between the daily sessions of GNSS-observation, the error the height determination is about 5 mm and it depends not only on the distance between points. The heights of quasigeoid, as the heights of points from GNSS-leveling, are always defined as absolute, that is, from the accepted level surface. The position of the level surface (Baltic system of heights 1977) is determined with bigger error, than the geodetic heights H from the surface of the ellipsoid (WGS-84), what can be concluded from the research. This way, it is proposed to determine the relative heights or elevations over the reference point. The study of definition accuracy of points’ heights from processing GNSS-observations prove that if daily sessions of observation are performed, the error of determination of geodetic point’s height can reach up to 5 mm. Thus, the accuracy of GNSS-leveling, that is, of determination of the geoid’s height, can increase the error by 5 mm at a distance of 10 km.

1. Druzjuk V., Mazur A., Trevoho I., Tsyupak I. Suchasni geodezychni prylady i tehnologii': naukovo-tehnichne metrologichne zabezpechennja [Modern surveying instruments and technology, scientific and technical metrological provision]. Metrologija ta prylady [Metrology and instruments]. 2010, no.3, pp. 19–26.

2. Zakon Ukrayiny "Pro topohrafo-heodezychnu i kartohrafichnu diyal'nist" [The Law of Ukraine "On surveying and mapping activities" ]. KMU. Resolution no. 379, May 27, 2015

3. Zubarev A. Je., Lebedev S.V., Nadezhdina I.E., Fedoseev Ju.E. Sovremennye problemy obespechenija territorij vysokotochnymi znachenijami vysot. [Modern problems of areas with precision values of heights]. Geoprofi [Geoprofi]. 2012, no. 3, pp. 54–57.

4. Instrukcija po nivelirovaniju I, II, III i IV klassov [Manual leveling I, II, III and IV klassov]. Moscow: Nedra [Moscow: Nedra]. 1990, 160 p.

5. Karpins'kyy Yu., Kucher O., Zayets' I. Obgruntuvannya metodu ta pobudova transformatsiynoho polya peretvorennya koordynat mizh systemamy SK-42 ta USK2000 [Justification of the method of transformation and building of the field coordinate transformation between systems SC-42 and USK2000] [Text] Geodesy, cartography and aerial photography. 2013, issue78, pp. 169–172.

6. Kostec'ka Ja., Pishko Ju. Do pytannja tochnosti dovzhyn vektoriv, otrymanyh za rezul'tatamy vidnosnyh GPS-sposterezhen' dvochastotnymy pryjmachamy [On the question of the accuracy of the lengths of the vectors obtained results relative observation dual-frequency GPS-receivers].Suchas. dosjagnennja geodez. nauky ta vyr-va: zb. nauk. pr. Zah. geodez. t-va UTGK [Modern achievements of geodetic science and industry: Coll. Science. pr. UTHK Western geodesic company]. 2009, issue 1, pp. 92–97.

7. Kostec'ka Ja., Pishko Ju., Geshel' D. Zalezhnist' tochnosti vyznachennja polozhennja punktiv u suputnykovyh merezhah vid tryvalosti seansiv sposterezhen' [The dependence of the accuracy of the paragraphs in satellite networks duration of observation sessions]. Suchas. dosjagnennja geodez. nauky ta vyr-va [Modern achievements of geodetic science and industry]. 2011, issue 2, pp. 96–102.

8. Kostec'ka Ja., Pishko Ju., Vplyv typu efemeryd na tochnist' vyznachennja polozhennja punktiv suputnykovyh merezh [Influence of the type of ephemerides on the accuracy of paragraphs satellite networks]. Suchas. dosjagnennja geodez. nauky ta vyr-va: zb. nauk. pr. Zah. geodez. t-va UTGK [Modern achievements of geodetic science and industry]. 2013, issue 1, pp. 67–69.

9. Kucher O. V., Zayets' I. M., Stopkhay Yu. A., Renkevych O. V. Peretvorennya koordynat iz derzhavnoyi heodezychnoyi systemy u svitovu systemu WGS-84 [The transformation of the state geodetic coordinate system into the global system WGS-84 ]. Visnyk heodeziyi ta kartohrafiyi [Journal of Geodesy and Cartography]. 2002, no. 3, pp. 8–14.

10. Kucher O. V., Kurylyak I. S., Marchenko O. M. Pro peretvorennya koordynat iz systemy SK-42 v systemu USK-2000 [On the coordinate transformation from the system IC-42 in USC-2000] [Text], Visnyk heodeziyi ta kartohrafiyi [Journal of Geodesy and Cartography]. 2009, no. 2, pp. 6–13.

11. Kucher O. V, Marchenko D. O., Zajec' I. M. Pro vykorystannja global'nyh modelej EGM08 ta EGG08 dlja vyznachennja vysot kvazigeoi'da na terytorijuUkrai'ny [On the use of global models EGM08 and EGG08 to determine the heights quasigeoid to Ukraine]. Visnyk geodezii' i kartografii' [Bulletin of Surveying and kartografy]. 2012, no. 4, pp. 13–17.

12. Marchenko O. M., Kucher O. V., Renkevych O. V. Rezul'taty pobudovy kvazigeoi'da dlja regionu Ukrai'ny (UKG2006) [Results for constructing quasigeoid region of Ukraine (UKH2006)]. Visn. geodezii' ta kartografii [Bulletin of Surveying and kartografy]. 2007, no. 2, pp. 3–13.

13. Marchenko O. M., Kucher O. V., Marchenko D. O., Rezul'taty utochnennja kvazigeoi'da UKG2012 dlja terytorii' Ukrai'ny [Results for clarification quasigeoid UKH2012 in Ukraine ].Visnyk geodezii' i kartografii' [Bulletin of Surveying and kartografy]. 2013, no. 3, pp. 3–10.

14. Marchenko O. M., Tretjak K.R., Jarema N.P. Referencni systemy v geodezii': navch. posibnyk [The referents systems in geodesy, teach. Manual]. L'viv: Vydavnyctvo L'vivs'koi' politehniky [Lviv Polytechnic National University Publishing House], 2013, 216 p.

15. Trevoho I. S., Tsyupak I. M. Problemy koordynatno-chasovogo prostoru pry suputnykovyh i nazemnyh geodezychnyh vymirjuvannjah [Coordinate and time in space satellite and terrestrial geodetic measurements]. Suchasni dosjagnennja geodezychnoi' nauky ta vyrobnyctva [Modern achievements of geodetic science and industry]. L'viv: Nac. universytet "L'vivs'ka politehnika" [Lviv Polytechnic Nat. University]. 2014, issue II (28), pp. 24–28.

16. Trevoho I. S., Tsyupak I. M. Analiz rezul'tativ novyh ekspedycij na metrologichnyh ob'jektah naukovogo geodezychnogo poligonu [Analysis of new expeditions to sites metrological research surveying Landfill ]. Suchasni dosjagnennja geodezychnoi' nauky ta vyrobnyctva. L'viv: Nac. universytet "L'vivs'ka politehnika" [Lviv Polytechnic Nat. University]. 2015, issue I (29), pp. 66–69.

17. Turchak L. I., Plotnikov P.V. Osnovy chislennyh metodov [Basics of numerical methods]. uchebn. posob., 2-e izd., pererab. i dop.- M.: FIZMATLIT, 2003, 304 p. ISBN 5-9221-0153-6.

18. Tsyupak I. M. Tochnist' vyznachennja koordynat punktiv i dovzhyn linij za sesijamy GPS-sposterezhen' riznoi' tryvalosti [The accuracy of coordinates of points and lengths of lines for GPS-observation sessions of varying lengths]. Suchasni dosjagnennja geodezychnoi' nauky ta vyrobnyctva [Modern achievements of geodetic science and industry]. L'viv: Vydavnyctvo L'vivs'koi' politehniky, 2012, issue I (23), pp. 57–59.

19. Jakovlev N. V. Vysshaja geodezija. Uch. dlja vuzov [Higher Geodesy. Textbook for vuzov]. Moscow: Nedra, 1989, 445 p.

20. Novak P., J. Klokocnik, J. Kostelecky, А. Zeman Testing EGM08 using Czech GPS/leveling data. Newton's Bulletin, 2009, no. 4, pp. 126–132, ISSN 1810-8555.

21. Rio M-H., Hernandez F. A mean dynamic topography computed over the world ocean from altimetry, in situ measurements, and a geoid model. Journal of Geophysical Research. 2004, Vol. 109, pp. C12032, doi:10.1029/ 2003JC002226.

22. Uzun S. The Reliability of Surface Fitting Methods in Orthometric Height Determination from GPS Observations. Sibel Uzun, Leyla Çakir. Paper proceedings on XXIII FIG Congress "Shaping the Change".- Munich, Germany, October 8-13,2006 (http://www.fig.net/resources/proceedings/fig_proceedings/fig2006/papers/...

23. Haijun Xu, Yongzhi Zhang, Hurong Duan. Gravity gradient distribution in mainland China from GOCE satellite gravity gradiometry data. Geodesy and Geodynamics. 2015, V. 6, Issue 1, pp. 41–45.

https://doi.org/10.1016/j.geog.2015.01.001