National report of LITHUANIA

THE 4th BALTIC SURVEYORS FORUM , 2013, Ventspils, LATVIA

Eimuntas ParseliunasGeodetic Institute of Vilnius Technical University

eimis@vgtu.lt

Transition to European Vertical Reference System – EVRS:

Status of the geodetic vertical control of Lithuania and further movements

Outline

•General ideas

•World Geodetic Vertical Datum and System

•Local (European) Vertical Reference System

•National Geodetic Vertical Network

•Further movements

General ideas

Approaches for the construction and unification of Geodetic Vertical Reference Systems and Frames:

• Spirit leveling • Gravity field

Marker of the vertical reference frame

Physical height difference

Ellipsoidal height difference and geoid

model

Benchmark Precise levelings and gravimetric observations

(leveling approach)

GNSS

(gravity field approach)

Tide gauge Oceanographic model Satellite altimetry

Ellipsoidal height, orthometric height, local geoid, vertical datum...

General ideas

General ideas

Geopotential number

Dynamic height

Orthometric height

Nominal value of gravity at mid-latitude

Average value of gravity along the plumb line

Normal height

Average value of normal gravity along the normal plumb line

m2s-2

General ideas

As there is a similar problem for the uncertainty in the topographic density distribution in determining orthometric heights (but not for normal heights), we conclude that a normal height system is the best choice for a future height system. Once the normal gravity field is defined, the normal heights and the quasigeoid can be determined without any error stemming from the topographic mass distribution, and the quasigeoid can be estimated more precisely than the geoid as the reference surface.

L. E. Sjöberg. The geoid or quasigeoid – which reference surface should be preferred for a national height system? Journal of Geodetic Science, 3(2), 2013, 103-109

World Geodetic Vertical Datum and System

World Geodetic Vertical Datum and System

Different teams computed W0 using the same input data, but their own methodologies:

Input data Mean sea surface models (MSS): CLS11 (Schaeffer et al. 2012) DTU10 (Andersen 2010)

Global gravity models (GGM): EGM2008 (Pavlis et al, 2012) EIGEN6C (Förste et al. 2011) GOCO3S (Mayer-Gürr et al. 2012)

World Geodetic Vertical Datum and SystemSome examples of W0 estimates

World Geodetic Vertical Datum and System

The reference level W0 for potential differences can arbitrarily be appointed. However, to get the worldwide consistency desired within a global vertical reference system, the selected W0 value must be realisable with high-precision at any time and anywhere around the world.

Therefore, it is necessary to estimate it from real observations of the Earth's gravity field and surface.

The uniqueness, reliability and repeatability of the global reference level W0 (or global geoid) can only be guaranteed by introducing specific conventions (like any other reference system!). On the contrary, there will exist as many height systems as W0 computations.

Remarks on W0

World Geodetic Vertical Datum and System

All the computations are delivering very close results (around 62 636 854 m2s-2), but there are still differences of about 0,5 m2s-2 (~ 5 cm).

It is necessary to start defining the standards and conventions for a formal recommendation on W0.

Final recommendation (till the end of 2013):

62 636 854,0 +/- 0,2 m2s-2

But...Canada: November 2013, CGVD2013 with 62 636 856,0 m2s-2

USA till 2020 also with 62 636 856,0 m2s-2

World Geodetic Vertical Datum and System

(EGM96)

World Geodetic Vertical Datum and System

Project

„Investigations of the requirements for a future 5 mm (quasi)geoid model“

has recently been started within the Nordic Geodetic Commission (NKG).

The NKG gravity database will soon be updated in connection with theNKG-project „Computation of the NKG2014 geoid model“.

Local (European) Vertical Reference System

Spirit leveling ApproachEVRF2007

Local (European) Vertical Reference System

Local (European) Vertical Reference System

Local (European) Vertical Reference System

Spirit leveling approach Transformation parameter

Estimation of 3 parameters (plane) as transformation parameters between the national

vertical reference frames and EVRF2007

http://www.crs-geo.eu

Local (European) Vertical Reference System

Local (European) Vertical Reference System

Local (European) Vertical Reference System

Local (European) Vertical Reference System

Local (European) Vertical Reference System

Local (European) Vertical Reference System

National Geodetic Vertical Network (1)

Lithuanian vertical (height) system is still not adopted.

The project of The Resolution of the Government of Lithuania is prepared!

It is based on EVRS Conventions 2007.

National Geodetic Vertical Network (1)

10 datum points

National Geodetic Vertical Network (1)

Data of datum points

National Geodetic Vertical Network (1)

National Geodetic Vertical Network (3)

National Geodetic Vertical Network (11)

National Geodetic Vertical Network (12)

National Geodetic Vertical Network (13)

National Geodetic Vertical Network (14)

Differences between some height systems

National Geodetic Vertical Network (14)

Precise levelling in 2009-2011 (in green) and near future plans (in red)

Vertical network (1st and 2nd order)

300000 350000 400000 450000 500000 550000 600000 650000

6000000

6050000

6100000

6150000

6200000

6250000

Vertical network (1st and 2nd order)

Red lines – foreseen 2nd order lines

Vertical network - numbers

Total lenght of lines – 3100 km:

Ready - 300 km (in 2007) + 300 km (in 2012)

Foreseen – 2200 km (in 2013-2015)

Characteristics of projected 2nd order Network

Total number of points - 3300 (new –2800)

•Lithuanian state geodetic vertival network fits to the requirements of the modern society

•It necessary to speed up the adoption of the Vertical (height) and Gravity systems in Lithuania

•The densification of the first order vertical network should be executed to fulfill the all needs of the geodesy science

Conclusions

•Adoption of vertical (height) and gravity systems – 2013

•Quasigeoid model (2 cm) - 2014

•NKG GNSS campaign – 2013

•LitPOS modernization – 2013-2015

•Second order vertical network – 2013-2015

•Absolute gravity measurements at Vilnius, Panevezys and Klaipeda – 2013

•Gravity survey – 2016-2018

•GNSS campaign at vertical network points - 2019

•Quasigeoid model (5mm) - 2020

Future plans

Thanks…

Thank you for your attention!