New gravity control in Poland – needs, the concept and the design

Abstract

Abstract:The existing Polish gravity control (POGK) established in the last few years of 20 th century according to the international standards is spanned on 12 absolute gravity stations surveyed with four different types of absolute gravimeters. Relative measurements performed by various groups on nearly 350 points of POGK with the use of LaCoste&Romberg (LCR) gravimeters were linked to those 12 stations. The construction of the network, in particular the limited number of non homogeneously distributed absolute gravity stations with gravity determined with different instruments in different epochs is responsible for systematic errors in g on POGK stations. The estimate of those errors with the use of gravity measurements performed in 2007-2008 is given and their possible sources are discussed.The development of absolute gravity measurement technologies, in particular instruments for precise fi eld absolute gravity measurements, provides an opportunity to establish new type of gravity control consisting of stations surveyed with absolute gravimeters. New gravity control planned to be established in 2012-2014 will consist of 28 fundamental points (surveyed with the FG5 -gravimeter), and 169 base points (surveyed with the A10 gravimeter). It will fulfi ll recent requirements of geodesy and geodynamics and it will provide good link to the existing POGK. A number of stations of the new gravity control with precisely determined position and height will form the national combined geodetic network.Methodology and measurement schemes for both absolute gravimeters as well as the technology for vertical gravity gradient determinations in the new gravity control were developed and tested. The way to assure proper gravity reference level with relation to ICAG and ECAG campaigns as well as local absolute gravimeter comparisons are described highlighting the role of metrology in the project. Integral part of the project are proposals of re-computation of old gravity data and their transformation to a new system (as 2 nd order network) as well as a defi nition of gravity system as "zero-tide" system. Seasonal variability of gravity has been discussed indicating that the effects of environmental changes when establishing modern gravity control with absolute gravity survey cannot be totally neglected.

Modernization of the basic gravimetric control network Polish Geological Institute – implementing a modern international gravimetric system and relationship with the historical Potsdam system

“…The network of absolute points was established with a non-homogeneous set of absolute ballistic gravimeters, therefore in this control network there were some errors caused by non-homogenous reference levels. However, adjustment of errors to up to 0.014 mGal was obtained with the accuracy of g determination at absolute points of about 0.005 mGal (Sas-Uhrynowski et al, 2000;Kryński et al, 2013). Each point had a separate pillar, which facilitated the relative measurements.…”

The contribution of an urban gravity survey to the determinable perspective of Athens city (Greece) underground structure

“…In the past, several authors (e.g., [8,17,23,45,46,74,80,83]. have discussed the establishment of absolute gravity bases networks, in several areas of the world, mostly for quite larger areas.…”

Geodynamics

“…Однією з основних вимог є вимога щодо точності представлення характеристик гравітаційного поля Землі. Так, актуальним завданням є створення моделей гравітаційного поля Землі, які б забезпечували точність визначення аномалій прискорення вільного падіння, висот квазігеоїда і складових відхилень прямовисних ліній із середніми квадратичними похибками 0,3-0,5 мГал, 0,1-0,3 м і 0,05-0,1" відповідно [ICGEM, Krynski, 2013].…”