Transcript National report of LITHUANIA Eimuntas Parseliunas Geodetic
National report of LITHUANIA
Transition to European Vertical Reference System – EVRS:
Status of the geodetic vertical control of Lithuania and further movements Eimuntas Parseliunas
Geodetic Institute of Vilnius Technical University [email protected]
THE 4th BALTIC SURVEYORS FORUM
, 2013, Ventspils, LATVIA
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
Benchmark Tide gauge
Physical height difference Ellipsoidal height difference and geoid model
GNSS Precise levelings and gravimetric observations (leveling approach) Oceanographic model (gravity field approach) Satellite altimetry
General ideas
Ellipsoidal height, orthometric height, local geoid, vertical datum...
General ideas
m 2 s -2
Geopotential number
Dynamic height Nominal value of gravity at mid-latitude Orthometric height Average value of gravity along the plumb line Normal height Average value of normal gravity along the normal plumb line
General ideas
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 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
.
World Geodetic Vertical Datum and System
World Geodetic Vertical Datum and System
Different teams computed W 0 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 System Some examples of W 0 estimates
World Geodetic Vertical Datum and System Remarks on W 0
The reference level W 0 for potential differences
can arbitrarily be appointed
. However, to get the worldwide consistency desired within a global vertical reference system, the selected
W 0 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 W 0 (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 W 0 computations.
World Geodetic Vertical Datum and System
All the computations are delivering very close results (
around 62 636 854 m 2 s -2
), but there are still differences of about
0,5 m 2 s -2
(~ 5 cm). It is necessary to start defining the standards and conventions for a formal recommendation on W 0 .
Final recommendation (till the end of 2013):
62 636 854,0 +/- 0,2
m 2 s -2
But...
Canada
: November 2013, CGVD2013 with
62 636 856,0 m 2 s -2 USA
till 2020 also with
62 636 856,0 m 2 s -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 the NKG-project „
Computation of the NKG2014 geoid model“
.
Local (European) Vertical Reference System
Spirit leveling Approach EVRF2007
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) 6250000 6200000 6150000 6100000 6050000 6000000 300000 350000 400000 450000 500000 550000 600000 650000
Vertical network (1st and 2nd order) Red lines – foreseen 2nd order lines
Vertical network - numbers Characteristics of projected 2nd order Network Total lenght of lines – 3100 km: Ready - 300 km (in 2007) + 300 km (in 2012)
Foreseen – 2200 km (in 2013-2015)
Total number of points - 3300 (new –2800)
Conclusions
•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
Future plans
•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
Thanks…