Magyarország 100 évvel ezelőtt létesített első gravimetriai főalappontjának újramérése a Műegyetemen
Date: 2018
Subject: first gravity reference station
gravity
Oltay Károly
első gravitációs főalappont
nehézségi térerősség
gravity
Oltay Károly
első gravitációs főalappont
nehézségi térerősség
Abstract:
The first gravity reference station of
Hungary was established by Károly
Oltay, professor and head of former
Department of Geodesy, Technical
University of Budapest. The station
was located in the pendulum hall and
its gravity value (g = 980 852 mGal)
was derived in 1915 from relative
pendulum measurements with respect
to the reference station at Geodetic
Institute in Potsdam. The network of
European gravity reference stations
was adjusted by C. Morelli in the
1940's and he got g = 980 853 mGal
for the station established by Oltay.
This value only slightly differs from
the one obtained by Finnish professor
R.A. Hirvonen (g = 980 853.3 mGal),
who used isostatic reduction in his
calculations.
The pendulum hall was
reconditioned in 2016, during which
the reference station was identified
and restored. Gravity was measured
at the reference station between
26–27 May, 2016 with the FG5X (No.
251) absolute gravity meter by staff
members of the Czech Geodetic
Observatory (Pecny, Ondrejov). Vertical
gravity gradient was also required to
be measured at the station to reduce
gravity measurements to the benchmark
and to compare with the old g
value. The measured vertical gravity
gradient (–0.3091 mGal/m) served
on the one hand to calculate g for the
benchmark (allowing our reference
station to be fit into the present
operative gravity base network of
Hungary [MGH-2013]). On the other
hand it facilitated calculating g for
the benchmark established by Oltay
for comparisons. When the systematic
difference of –14 mGal between the
reference system of Potsdam and
the absolute system (or the value of
–13.94 mGal based on local studies)
is accounted for, the value obtained by
us in 2016 (g = 980 839 431.55 μGal)
agrees well with the value obtained
by Oltay.